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1. A Growing Braking Index and Spin-down Swings for the Pulsar PSR B0540–69

Author: Cristóbal M. Espinoza, Lucien Kuiper, Wynn C. G. Ho, Danai Antonopoulou, Zaven Arzoumanian, Alice K. Harding, Paul S. Ray, and George Younes
Subjects: Compact objects, Neutron stars, Pulsars, Rotation powered pulsars, Astrophysics, QB460-466
Abstract: The way pulsars spin down is not understood in detail, but a number of possible physical mechanisms produce a spin-down rate that scales as a power of the rotation rate ( $\dot{\nu }\propto -{\nu }^{n}$ ), with the power-law index n called the braking index. PSR B0540−69 is a pulsar that in 2011, after 16 yr of spinning down with a constant braking index of 2.1, experienced a giant spin-down change and a reduction of its braking index to nearly zero. Here, we show that, following this episode, the braking index monotonically increased during a period of at least 4 yr and stabilized at ∼1.1. We also present an alternative interpretation of a more modest rotational irregularity that occurred in 2023, which was modeled as an anomalous negative step of the rotation rate. Our analysis shows that the 2023 observations can be equally well described as a transient swing of the spin-down rate (lasting ∼65 days), and the Bayesian evidence indicates that this model is strongly preferred.
Published: 2024
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2. First Detection of Polarization in X-Rays for PSR B0540-69 and Its Nebula

Author: Fei Xie, Josephine Wong, Fabio La Monaca, Roger W. Romani, Jeremy Heyl, Philip Kaaret, Alessandro Di Marco, Niccolò Bucciantini, Kuan Liu, Chi-Yung Ng, Niccolò Di Lalla, Martin C. Weisskopf, Enrico Costa, Paolo Soffitta, Fabio Muleri, Matteo Bachetti, Maura Pilia, John Rankin, Sergio Fabiani, Iván Agudo, Lucio A. Antonelli, Luca Baldini, Wayne H. Baumgartner, Ronaldo Bellazzini, Stefano Bianchi, Stephen D. Bongiorno, Raffaella Bonino, Alessandro Brez, Fiamma Capitanio, Simone Castellano, Elisabetta Cavazzuti, Chien-Ting Chen, Stefano Ciprini, Alessandra De Rosa, Ettore Del Monte, Laura Di Gesu, Immacolata Donnarumma, Victor Doroshenko, Michal Dovčiak, Steven R. Ehlert, Teruaki Enoto, Yuri Evangelista, Riccardo Ferrazzoli, Javier A. Garcia, Shuichi Gunji, Kiyoshi Hayashida, Wataru Iwakiri, Svetlana G. Jorstad, Vladimir Karas, Fabian Kislat, Takao Kitaguchi, Jeffery J. Kolodziejczak, Henric Krawczynski, Luca Latronico, Ioannis Liodakis, Simone Maldera, Alberto Manfreda, Frédéric Marin, Andrea Marinucci, Alan P. Marscher, Herman L. Marshall, Francesco Massaro, Giorgio Matt, Ikuyuki Mitsuishi, Tsunefumi Mizuno, Michela Negro, Stephen L. O’Dell, Nicola Omodei, Chiara Oppedisano, Alessandro Papitto, George G. Pavlov, Abel L. Peirson, Matteo Perri, Melissa Pesce-Rollins, Pierre-Olivier Petrucci, Andrea Possenti, Juri Poutanen, Simonetta Puccetti, Brian D. Ramsey, Ajay Ratheesh, Oliver J. Roberts, Carmelo Sgrò, Patrick Slane, Gloria Spandre, Douglas A. Swartz, Toru Tamagawa, Fabrizio Tavecchio, Roberto Taverna, Yuzuru Tawara, Allyn F. Tennant, Nicholas E. Thomas, Francesco Tombesi, Alessio Trois, Sergey S. Tsygankov, Roberto Turolla, Jacco Vink, Kinwah Wu, Silvia Zane, IXPE Collaboration, Zorawar Wadiasingh, Wynn C. G. Ho, Alice K. Harding, Keith C. Gendreau, and Zaven Arzoumanian
Subjects: Pulsars, Pulsar wind nebulae, Polarimetry, Astrophysics, QB460-466
Abstract: We report on X-ray polarization measurements of the extragalactic Crab-like PSR B0540-69 and its Pulsar Wind Nebula (PWN) in the Large Magellanic Cloud, using a ∼850 ks Imaging X-ray Polarimetry Explorer (IXPE) exposure. The PWN is unresolved by IXPE. No statistically significant polarization is detected for the image-averaged data, giving a 99% confidence polarization upper limit (MDP _99 ) of 5.3% in the 2–8 keV energy range. However, a phase-resolved analysis detects polarization for both the nebula and pulsar in the 4–6 keV energy range. For the PWN defined as the off-pulse phases, the polarization degree (PD) of (24.5 ± 5.3)% and polarization angle (PA) of (78.1 ± 6.2)° is detected at 4.6 σ significance level, consistent with the PA observed in the optical band. In a single on-pulse window, a hint of polarization is measured at 3.8 σ with PD of (50.0 ± 13.1)% and PA of (6.2 ± 7.4)°. A “simultaneous” PSR/PWN analysis finds two bins at the edges of the pulse exceeding 3 σ PD significance, with PD of (68 ± 20)% and (62 ± 20)%; intervening bins at 2–3 σ significance have lower PD, hinting at additional polarization structure.
Published: 2024
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3. The Gamma-Ray Pulsar Phenomenology in View of 3D Kinetic Global Magnetosphere Models

Author: Constantinos Kalapotharakos, Zorawar Wadiasingh, Alice K. Harding, and Demosthenes Kazanas
Subjects: Pulsars, Gamma-rays, Gamma-ray telescopes, Computational methods, Neutron stars, Astrophysics, QB460-466
Abstract: We develop kinetic plasma models of pulsar magnetospheres with magnetic-field-line-dependent plasma injection that reveal the importance of various magnetosphere regions in regulating the γ -ray emission. We set different particle injection rates for the so-called open, closed, and separatrix zones. Moderate particle injection rates in open and closed zones ensure a global field structure close to the force-free structure, while the dissipation occurs mainly in and around the equatorial current sheet. The particles that are injected into the separatrix zone affect the particle populations that enter the equatorial current sheet region, and therefore the corresponding accelerating electric fields, particle energies, the spectral cutoff energy, and γ -ray efficiency. The separatrix zone models reproduce the recently discovered fundamental plane of γ -ray pulsars consistent with curvature radiation emission, the γ -ray light-curve shapes, and the radio-lag versus peak-separation correlation reported in the Fermi second pulsar catalog. The model beaming factors indicate that the pulsar total γ -ray luminosities listed in the Fermi catalogs are overestimations of the actual ones. We find that the radiation reaction limited regime starts ceasing to govern the high-energy emission for $\dot{{ \mathcal E }}\lesssim {10}^{34}\,\mathrm{erg}\,\,{{\rm{s}}}^{-1}$ . Our results also indicate that toward high magnetic inclination angles, the Y point around the rotational equator migrates well inside the light cylinder, sparking additional peaks in the γ -ray pulse profiles. We find that an equivalent enhanced particle injection beyond the Y point strengthens these features, making the model γ -ray light curves inconsistent with those observed.
Published: 2023
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4. A NICER View on the 2020 Magnetar-like Outburst of PSR J1846−0258

Author: Chin-Ping Hu, Lucien Kuiper, Alice K. Harding, George Younes, Harsha Blumer, Wynn C. G. Ho, Teruaki Enoto, Cristóbal M. Espinoza, and Keith Gendreau
Subjects: Neutron stars, Astrophysics, QB460-466
Abstract: We report on our monitoring of the strong-field magnetar-like pulsar PSR J1846−0258 with the Neutron Star Interior Composition Explorer (NICER) and the timing and spectral evolution during its outburst in 2020 August. Phase-coherent timing solutions were maintained from 2017 March through 2021 November, including a coherent solution throughout the outburst. We detected a large spin-up glitch of magnitude Δ ν / ν = 3 × 10 ^−6 at the start of the outburst and observed an increase in pulsed flux that reached a factor of more than 10 times the quiescent level, a behavior similar to that of the 2006 outburst. Our monitoring observations in 2020 June and July indicate that the flux was rising prior to the Swift announcement of the outburst on 2020 August 1. We also observed several sharp rises in the pulsed flux following the outburst and the flux reached quiescent level by 2020 November. The pulse profile was observed to change shape during the outburst, returning to the preoutburst shape by 2021. Spectral analysis of the pulsed emission of NICER data shows that the flux increases result entirely from a new blackbody component that gradually fades away while the power law remains nearly constant at its quiescent level throughout the outburst. Joint spectral analysis of NICER and simultaneous NuSTAR data confirms this picture. We discuss the interpretation of the magnetar-like outburst and origin of the transient thermal component in the context of both a pulsar-like and a magnetar-like model.
Published: 2023
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5. Exploring the MeV Sky With A Combined Coded Mask and Compton Telescope: the Galactic Explorer With A Coded Aperture Mask Compton Telescope (GECCO)

Author: Elena Orlando, Eugenio Bottacini, A.A. Moiseev, Arash Bodaghee, Werner Collmar, Torsten Ensslin, Igor V. Moskalenko, Michela Negro, Stefano Profumo, Seth W. Digel, David J. Thompson, Matthew G. Baring, Aleksey Bolotnikov, Nicholas Cannady, Gabriella A. Carini, Vincent Eberle, Isabelle A. Grenier, Alice K. Harding, Dieter Hartmann, Sven Herrmann, Matthew Kerr, Roman Krivonos, Philippe Laurent, Francesco Longo, Aldo Morselli, Bernard Philips, Makoto Sasaki, Peter Shawhan, Daniel Shy, Gerry Skinner, Lucas D. Smith, Floyd W. Stecker, Andrew Strong, Steven Sturner, John A. Tomsick, Zorawar Wadiasingh, Ricahrd S. Woolf, Eric Yates, Klaus-Peter Ziock, and Andreas Zoglauer
Subjects: Astrophysics, Physics of Elementary Particles and Fields
Abstract: The sky at MeV energies is currently poorly explored. Here we present an innovative mission concept that builds upon the heritage of past and current missions improving the sensitivity and, very importantly, the angular resolution. This consists in combining a Compton telescope and a coded-mask telescope. We delineate the motivation for such a concept and we define the scientific goals for such a mission. The Galactic Explorer with a Coded Aperture Mask Compton Telescope (GECCO) is a novel concept for a next-generation telescope covering hard X-ray and soft gamma-ray energies. The potential and importance of this approach that bridges the observational gap in the MeV energy range are presented. With the unprecedented angular resolution of the coded mask telescope combined with the sensitive Compton telescope, a mission such as GECCO can disentangle the discrete sources from the truly diffuse emission. Individual Galactic and extragalactic sources are detected. This also allows to understand the gamma-ray Galactic center excess and the Fermi Bubbles, and to trace the low-energy cosmic rays, and their propagation in the Galaxy. Nuclear and annihilation lines are spatially and spectrally resolved from the continuum emission and from sources, addressing the role of low-energy cosmic rays in star formation and galaxy evolution, the origin of the 511 keV positron line, fundamental physics, and the chemical enrichment in the Galaxy. Such an instrument also detects explosive transient gamma-ray sources, which, in turn, enables identifying and studying the astrophysical objects that produce gravitational waves and neutrinos in a multi-messenger context. By looking at a poorly explored energy band it also allows discoveries of new astrophysical phenomena.
Published: 2022
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6. X-Ray Burst and Persistent Emission Properties of the Magnetar SGR 1830-0645 in Outburst

Author: George Younes, Chin-Ping Hu, Karishma Bansal, Paul S. Ray, Aaron B. Pearlman, Franz Kirsten, Zorawar Wadiasingh, Ersin Göğüş, Matthew G. Baring, Teruaki Enoto, Zaven Arzoumanian, Keith C. Gendreau, Chryssa Kouveliotou, Tolga Güver, Alice K. Harding, Walid A. Majid, Harsha Blumer, Jason W. T. Hessels, Marcin P. Gawroński, Vladislavs Bezrukovs, and Arturs Orbidans
Subjects: Astrophysics
Abstract: We report on NICER X-ray monitoring of the magnetar SGR 1830−0645 covering 223 days following its 2020 October outburst, as well as Chandra and radio observations. We present the most accurate spin ephemerides of the source so far: ν = 0.096008680(2) Hz, $\dot{\n𝜈}=-6.2(1) x (10)^(-14) Hz/s, and significant second and third frequency derivative terms indicative of nonnegligible timing noise. The phase-averaged 0.8–7 keV spectrum is well fit with a double-blackbody (BB) model throughout the campaign. The BB temperatures remain constant at 0.46 and 1.2 keV. The areas and flux of each component decreased by a factor of 6, initially through a steep decay trend lasting about 46 days, followed by a shallow long-term one. The pulse shape in the same energy range is initially complex, exhibiting three distinct peaks, yet with clear continuous evolution throughout the outburst toward a simpler, single-pulse shape. The rms pulsed fraction is high and increases from about 40% to 50%. We find no dependence of pulse shape or fraction on energy. These results suggest that multiple hot spots, possibly possessing temperature gradients, emerged at outburst onset and shrank as the outburst decayed. We detect 84 faint bursts with NICER, having a strong preference for occurring close to the surface emission pulse maximum—the first time this phenomenon is detected in such a large burst sample. This likely implies a very low altitude for the burst emission region and a triggering mechanism connected to the surface active zone. Finally, our radio observations at several epochs and multiple frequencies reveal no evidence of pulsed or burst-like radio emission.
Published: 2022
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7. Very-high-energy Emission from Pulsars

Author: Alice K. Harding, Christo Venter, and Konstantinos Kalapotharakos
Subjects: Astrophysics
Abstract: Air-Cherenkov telescopes have detected pulsations at energies above 50 GeV from a growing number of Fermi pulsars. These include the Crab, Vela, PSR B1706−44, and Geminga, with the first two having pulsed detections above 1 TeV. In some cases, there appears to be very-high-energy (VHE) emission that is an extension of the Fermi spectra to high energies, while in other cases, additional higher-energy spectral components that require a separate emission mechanism may be present. We present results of broadband spectral modeling using global magnetospheric fields and multiple emission mechanisms that include synchro-curvature (SC) and inverse Compton scattered (ICS) radiation from accelerated particles (primaries) and synchrotron self-Compton (SSC) emission from lower-energy pairs. Our models predict three distinct VHE components: SC from primaries whose high-energy tail can extend to 100 GeV, SSC from pairs that can extend to several TeV, and ICS from primary particles accelerated in the current sheet that scatter pair synchrotron radiation, which appears beyond 10 TeV. Our models suggest that H.E.S.S.-II and MAGIC have detected the high-energy tail of the primary SC component that produces the Fermi spectrum in Vela, Geminga, and PSR B1706−44. We argue that the ICS component peaking above 10 TeV from Vela has been seen by H.E.S.S. Detection of this emission component from the Crab and other pulsars is possible with the High Altitude Water Cherenkov Observatory and Cherenkov Telescope Array, and will directly measure the maximum particle energy in pulsars.
Published: 2021
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8. Constraining the Neutron Star Mass–Radius Relation and Dense Matter Equation of State with NICER. III. Model Description and Verification of Parameter Estimation Codes

Author: Slavko Bogdanov, Alexander J. Dittmann, Wynn C. G. Ho, Frederick K. Lamb, Simin Mahmoodifar, M. Coleman Miller, Sharon M. Morsink, Thomas E. Riley, Tod E. Strohmayer, Anna L. Watts, Devarshi Choudhury, Sebastien Guillot, Alice K Harding, Paul S. Ray, Zorawar Wadiasingh, Michael T. Wolff, Craig B. Markwardt, Zaven Arzoumanian, and Keith C. Gendreau
Subjects: Astrophysics
Abstract: We describe the X-ray pulse profile models we use and how we use them to analyze Neutron Star Interior Composition Explorer(NICER)observations of rotation-powered millisecond pulsars to obtain information about the mass–radius relation of neutron stars and the equation of state of the dense matter in their cores. Here we detail our modeling of the observed profile of PSR J0030+0451 that we analyzed in Miller et al. and Riley et al. and describe a cross-verification of computations of the pulse profiles of a star with R/M 3, in case stars this compact need to be considered in future analyses. We also present our early cross-verification efforts of the parameter estimation procedures used by Miller et al. and Riley et al. by analyzing two distinct synthetic data sets. Both codes yielded credible regions in the mass–radius plane that are statistically consistent with one another, and both gave posterior distributions for model parameter values consistent with the values that were used to generate the data. We also summarize the additional tests of the parameter estimation procedure of Miller et al. that used synthetic pulse profiles and the NICER pulse profile of PSR J0030+0451. We then illustrate how the precision of mass and radius estimates depends on the pulsar’s spin rate and the size of its hot spot by analyzing four different synthetic pulse profiles. Finally, we assess possible sources of systematic error in the estimates made using this technique, some of which may warrant further investigation.
Published: 2021
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9. Discovery of Soft X-ray Pulsations from PSR J1231-1411 using NICER

Author: Paul S Ray, Sebastien Guillot, Scott M Ransom, Matthew Kerr, Slavko Bogdanov, Alice K Harding, Michael T Wolff, Christian Malacaria, Keith C Gendreau, Zaven Arzoumanian, Craig Markwardt, Yang Soong, and John P Doty
Subjects: Astrophysics
Abstract: We report the discovery of soft X-ray pulsations from the nearby millisecond pulsar PSR J1231−1411 using the Neutron Star Interior Composition Explorer (NICER). The pulsed emission is characterized by a broad and asymmetric main pulse and a much fainter secondary interpulse, with a total pulsed count rate of 0.055 c s−1 in the 0.35–1.5 keV band. We analyzed Fermi Large Area Telescope (LAT) data to update the pulse timing model covering 10 yr of data and used that model to coherently combine NICER data over a year of observations. Spectral modeling suggests that the flux is dominated by thermal emission from a hot spot (or spots) on the neutron star surface. The phase relationship between the X-ray pulse and the radio and γ rays provides insight into the geometry of the system.
Published: 2019
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10. Neutron Star Interior Composition Explorer X-Ray Timing of the Radio and Gamma-ray Quiet Pulsars PSR J1412+7922 and PRS J1849-0001

Author: Slavko Bogdanov, Wynn C G Ho, Teruaki Enoto, Sebastien Guillot, Alice K Harding, Guarava K Jaiswal, Christian Malacaria, Sridhar Manthripragada, Zaven Arzoumanian, and Keith C Gendreau
Subjects: Astrophysics
Abstract: We present new timing and spectral analyses of PSR J1412+7922 (Calvera) and PSR J1849−0001, which are only seen as pulsars in X-rays, based on observations conducted with the Neutron Star Interior Composition Explorer. We obtain updated and substantially improved pulse ephemerides compared to previous X-ray studies, as well as spectra that can be well fit by simple blackbodies and/or a power law. Our refined timing measurements enable deeper searches for pulsations at other wavelengths and sensitive targeted searches by the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo for continuous gravitational waves from these neutron stars. Using the sensitivity of LIGO’s first observing run, we estimate constraints that a gravitational wave search of these pulsars would be obtained on the size of their mass deformation and r-mode fluid oscillation.
Published: 2019
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11. Broadband X-ray burst spectroscopy of the fast-radio-burst-emitting Galactic magnetar

Author: Gaurava K. Jaisawal, Keith C. Gendreau, Alice K. Harding, Chin-Ping Hu, George Younes, Beverly LaMarr, Lin Lin, Teruaki Enoto, J. Pope, Matthew G. Baring, Zaven Arzoumanian, Wynn C. G. Ho, Yuki Kaneko, James F. Steiner, Ersin Gogus, Zorawar Wadiasingh, J. Doty, Takashi Okajima, Walid A. Majid, Tolga Guver, Chryssa Kouveliotou, M. Saylor, Paul S. Ray, A. J. van der Horst, Sebastien Guillot, Oliver J. Roberts, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, Neutron Star Interior Composition Explorer, 010504 meteorology & atmospheric sciences, Fast radio burst, Astrophysics::High Energy Astrophysical Phenomena, Milky Way, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Magnetar, 01 natural sciences, Spectral line, Neutron star, 13. Climate action, 0103 physical sciences, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Spectroscopy, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Fermi Gamma-ray Space Telescope
Abstract: Magnetars are young, magnetically powered neutron stars that possess the strongest magnetic fields in the Universe. Fast radio bursts (FRBs) are extremely intense millisecond-long radio pulses of primarily extragalactic origin, and a leading attribution for their genesis focuses on magnetars. A hallmark signature of magnetars is their emission of bright, hard X-ray bursts of sub-second duration. On 27 April 2020, the Galactic magnetar SGR J1935+2154 emitted hundreds of X-ray bursts within a few hours. One of these temporally coincided with an FRB, the first known detection of an FRB from the Milky Way. Here, we present spectral and temporal analyses of 24 X-ray bursts emitted 13 hours prior to the FRB and seen simultaneously with the Neutron Star Interior Composition Explorer (NICER) mission of the National Aeronautics and Space Administration and with the Fermi Gamma-ray Burst Monitor (GBM) mission in their combined energy range of 0.2 keV to 30 MeV. These broadband spectra permit direct comparison with the spectrum of the FRB-associated X-ray burst (FRB-X). We demonstrate that all 24 NICER and GBM bursts are very similar temporally to the FRB-X, but strikingly different spectrally. The singularity of the FRB-X burst is perhaps indicative of an uncommon locale for its origin. We suggest that this event originated in quasi-polar open or closed magnetic field lines that extend to high altitudes. Twenty-four X-ray bursts from a Galactic magnetar simultaneously observed with NICER and Fermi permit a direct comparison to a later X-ray burst that was coincident with a fast radio burst (FRB). The FRB-related burst is spectrally distinct, pointing to an unusual point of emission.
Published: 2021
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12. Modelling Phase-resolved Spectra and Energy-dependent Light Curves of the Vela Pulsar to Scrutinize its GeV Emission Mechanism

Author: Monica Barnard, Constantinos Kalapotharakos, Christo Venter, Alice K. Harding, and Tyrel J. Johnson
Subjects: Energy dependent, Physics, Pulsar, Phase (waves), Astrophysics, Light curve, Vela, Mechanism (sociology), Spectral line
Published: 2021
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13. 'Spider' Millisecond Pulsar Binaries as Potential TeV Emitters

Author: Alice K. Harding, Matthew G. Baring, Christian J. T. van der Merwe, Christo Venter, and Zorawar Wadiasingh
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Light curve, Synchrotron, Spectral line, Galaxy, law.invention, Particle acceleration, Positron, Astrophysics - Solar and Stellar Astrophysics, Pulsar, Millisecond pulsar, law, Physics::Accelerator Physics, Astrophysics - High Energy Astrophysical Phenomena, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: Pulsar winds interacting with sources of external pressure are well-established as efficient and prolific TeV accelerators in our Galaxy. Yet, enabled by observations from Fermi-LAT, a growing class of non-accreting pulsars in binaries has emerged and these are likely to become apparent as TeV emitters in the CTA era. This class consists of the black widows and redbacks, binaries in which a millisecond pulsar interacts with its low-mass companion. In such systems, an intrabinary shock can form as a site of particle acceleration and associated nonthermal emission. We motivate why these sources are particularly interesting for understanding pulsar winds. We also describe our new multizone code which models the X-ray and gamma-ray synchrotron and inverse Compton spectral components for select spider binaries, including diffusion, convection, and radiative energy losses in an axially symmetric, steady-state approach. This new multizone code simultaneously yields energy-dependent light curves and orbital-phase-resolved spectra. It also better constrains the multiplicity of electron/positron pairs that have been accelerated up to TeV energies and are necessary to power orbitally-modulated synchrotron emission components between the X-rays and MeV/GeV bands potentially observed in some systems. This affords a more robust prediction of the expected high-energy and VHE gamma-ray flux. Nearby MSPs with hot or flaring companions may be promising targets for CTA, and it is possible that spider binaries could contribute to the observed AMS-02 energetic positron excess., Comment: Presented at the 37th International Cosmic Ray Conference (ICRC 2021)
Published: 2021
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14. Modeling Very-High-Energy Emission from Pulsars

Author: Alice K. Harding, Constantinos Kalapotharakos, and Christo Venter
Subjects: Physics, Pulsar, law, Millisecond pulsar, Astrophysics::High Energy Astrophysical Phenomena, Synchrotron radiation, Astrophysics, MAGIC (telescope), Vela, Spectral line, Synchrotron, Fermi Gamma-ray Space Telescope, law.invention
Abstract: Ground-based Air-Cherenkov telescopes have detected pulsations at energies above 50 GeV from a growing number of {\sl Fermi} pulsars. These include the Crab, Vela, PSR~B1706-44 and Geminga pulsar, with the first two having pulsed detections above 1 TeV. In some cases, there appears to be very-high-energy (VHE) emission that is an extension of the {\sl Fermi} spectra to higher energies, while in other cases, additional higher-energy spectral components that require a separate emission mechanism may be present. We will present results of broadband spectral modeling using global magnetosphere fields and multiple emission mechanisms that include synchro-curvature (SC) and inverse Compton scattered (ICS) radiation from accelerated particles (primaries) and synchrotron self-Compton (SSC) emission from lower-energy pairs. Our models predict three distinct VHE components: SC from primaries whose high-energy tail can extend to 100 GeV, SSC from pairs that can extend to several TeV and ICS from primary particles accelerated in the current sheet, scattering pair synchrotron radiation, that appears beyond 10 TeV. Model spectra show a wide range of VHE flux, with detectable pair SSC and primary ICS components expected for Crab-like pulsars and some millisecond pulsars but only a primary ICS component for Vela. Our models suggest that H.E.S.S.-II and MAGIC have detected the high-energy tail of the primary SC component that produces the {\sl Fermi} spectrum in Vela, Geminga and PSR B1706$-$44. We argue that the ICS component peaking above 10 TeV from Vela has been seen by H.E.S.S. Detection of this emission component from the Crab and other pulsars is possible with HAWC and CTA, and directly measures the maximum particle energy in pulsars.
Published: 2021
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15. A NICER View of the Massive Pulsar PSR J0740+6620 Informed by Radio Timing and XMM-Newton Spectroscopy

Author: Keith C. Gendreau, Sebastien Guillot, Ismaël Cognard, Anna L. Watts, Zaven Arzoumanian, Anna V. Bilous, Ronald A. Remillard, Julia Deneva, Takashi Okajima, Matthew Kerr, James M. Lattimer, Michael Loewenstein, Chanda Prescod-Weinstein, Renee M. Ludlam, Aditya Parthasarathy, Lucas Guillemot, Sharon M. Morsink, Wynn C. G. Ho, Timothy T. Pennucci, Ingrid H. Stairs, Slavko Bogdanov, Paul S. Ray, Scott M. Ransom, Devarshi Choudhury, Emmanuel Fonseca, Michael T. Wolff, Alice K. Harding, H. Thankful Cromartie, Craig B. Markwardt, Thomas E. Riley, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Photon, [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], Nuclear Theory, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, 01 natural sciences, Orbital inclination, Nuclear Theory (nucl-th), Pulsar, Millisecond pulsar, 0103 physical sciences, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Neutron Star Interior Composition Explorer, 010308 nuclear & particles physics, Astronomy and Astrophysics, Radius, Effective temperature, Astrophysics - Solar and Stellar Astrophysics, [SDU]Sciences of the Universe [physics], 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, Likelihood function
Abstract: We report on Bayesian estimation of the radius, mass, and hot surface regions of the massive millisecond pulsar PSR J0740$+$6620, conditional on pulse-profile modeling of Neutron Star Interior Composition Explorer X-ray Timing Instrument (NICER XTI) event data. We condition on informative pulsar mass, distance, and orbital inclination priors derived from the joint NANOGrav and CHIME/Pulsar wideband radio timing measurements of arXiv:2104.00880. We use XMM European Photon Imaging Camera spectroscopic event data to inform our X-ray likelihood function. The prior support of the pulsar radius is truncated at 16 km to ensure coverage of current dense matter models. We assume conservative priors on instrument calibration uncertainty. We constrain the equatorial radius and mass of PSR J0740$+$6620 to be $12.39_{-0.98}^{+1.30}$ km and $2.072_{-0.066}^{+0.067}$ M$_{\odot}$ respectively, each reported as the posterior credible interval bounded by the 16% and 84% quantiles, conditional on surface hot regions that are non-overlapping spherical caps of fully-ionized hydrogen atmosphere with uniform effective temperature; a posteriori, the temperature is $\log_{10}(T$ [K]$)=5.99_{-0.06}^{+0.05}$ for each hot region. All software for the X-ray modeling framework is open-source and all data, model, and sample information is publicly available, including analysis notebooks and model modules in the Python language. Our marginal likelihood function of mass and equatorial radius is proportional to the marginal joint posterior density of those parameters (within the prior support) and can thus be computed from the posterior samples., Comment: 40 pages, 16 figures (3 of which are figure sets), 1 animation, 2 tables. ApJL accepted version. Software: https://github.com/ThomasEdwardRiley/xpsi. Zenodo: https://doi.org/10.5281/zenodo.4697624. (v1 = submitted version; v2 = accepted version; v3 = metadata edits)
Published: 2021
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16. Enhanced x-ray emission coinciding with giant radio pulses from the Crab Pulsar

Author: Keith C. Gendreau, Alice K. Harding, Slavko Bogdanov, Yoshinori Yonekura, Hiroaki Misawa, Takahiko Aoki, Sebastien Guillot, Zaven Arzoumanian, Tomoaki Oyama, Steve Kenyon, Kazuhiro Takefuji, Zorawar Wadiasingh, Tolga Guver, R. S. Foster, Mamoru Sekido, Katsuaki Asano, Christian Malacaria, Shuta J. Tanaka, Yang Soong, Craig B. Markwardt, Takashi Okajima, Shota Kisaka, Natalia Lewandowska, Chin-Ping Hu, Fuminori Tsuchiya, Paul S. Ray, Hiroshi Takeuchi, Teruaki Enoto, Toshio Terasawa, Shinpei Shibata, Osamu Kameya, Munetoshi Tokumaru, Gaurava K. Jaisawal, Mareki Honma, Wynn C. G. Ho, Yasuhiro Murata, Walid A. Majid, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Multidisciplinary, Crab Pulsar, Astrophysics::High Energy Astrophysical Phenomena, X-ray, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Wavelength, Microsecond, Pulsar, 0103 physical sciences, Optical emission spectroscopy, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010306 general physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: Giant radio pulses (GRPs) are sporadic bursts emitted by some pulsars, lasting a few microseconds. GRPs are hundreds to thousands of times brighter than regular pulses from these sources. The only GRP-associated emission outside radio wavelengths is from the Crab Pulsar, where optical emission is enhanced by a few percent during GRPs. We observed the Crab Pulsar simultaneously at X-ray and radio wavelengths, finding enhancement of the X-ray emission by $3.8\pm0.7\%$ (a 5.4$\sigma$ detection) coinciding with GRPs. This implies that the total emitted energy from GRPs is tens to hundreds of times higher than previously known. We discuss the implications for the pulsar emission mechanism and extragalactic fast radio bursts., Comment: 63 pages, 23 figures, 7 Tables. Published in Science
Published: 2021
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17. Einstein@Home discovery of the gamma-ray millisecond pulsar PSR J2039–5617 confirms its predicted redback nature

Author: Mark Kennedy, O. Behnke, V. S. Dhillon, C. Choquet, D. Mata Sánchez, Jingwen Wu, Heinz-Bernd Eggenstein, T. R. Marsh, Alessandro Corongiu, Zorawar Wadiasingh, Guillaume Voisin, Rene P. Breton, Lucas Guillemot, L. Nieder, C. Aulbert, Roberto Mignani, J. Stringer, C. J. Clark, Alice K. Harding, H. Fehrmann, Benjamin William Allen, B. Machenschalk, ITA, USA, GBR, FRA, DEU, ESP, POL, Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), and Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)
Subjects: gamma-rays: stars, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, pulsars: individual (PSR J2039–5617), 01 natural sciences, stars: neutron, Pulsar, Millisecond pulsar, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, QC, QB, Physics, Orbital elements, High Energy Astrophysical Phenomena (astro-ph.HE), binaries: close, 010308 nuclear & particles physics, Compton scattering, Astronomy and Astrophysics, Orbital period, Light curve, Space and Planetary Science, Quadrupole, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract: The Fermi Large Area Telescope gamma-ray source 3FGL J2039.6$-$5618 contains a periodic optical and X-ray source that was predicted to be a "redback" millisecond pulsar (MSP) binary system. However, the conclusive identification required the detection of pulsations from the putative MSP. To better constrain the orbital parameters for a directed search for gamma-ray pulsations, we obtained new optical light curves in 2017 and 2018, which revealed long-term variability from the companion star. The resulting orbital parameter constraints were used to perform a targeted gamma-ray pulsation search using the Einstein@Home distributed volunteer computing system. This search discovered pulsations with a period of 2.65 ms, confirming the source as a binary MSP now known as PSR J2039$-$5617. Optical light curve modelling is complicated, and likely biased, by asymmetric heating on the companion star and long-term variability, but we find an inclination $i > 60��$, for a low pulsar mass between $1.1 M_{\odot} < M_{\rm psr} < 1.6 M_{\odot}$ and a companion mass of 0.15--0.22 $M_{\odot}$, confirming the redback classification. Timing the gamma-ray pulsations also revealed significant variability in the orbital period, which we find to be consistent with quadrupole moment variations in the companion star, suggestive of convective activity. We also find that the pulsed flux is modulated at the orbital period, potentially due to inverse Compton scattering between high-energy leptons in the pulsar wind and the companion star's optical photon field., 21 pages, 11 figures, published in MNRAS
Published: 2021
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18. The Mysterious Magnetospheres of Magnetars (INVITED)

Author: Zorawar Wadiasingh, Kun Hu, Alice K. Harding, Peter L. Gonthier, and Matthew G. Baring
Subjects: Physics, Neutron star, Photon, Stellar mass, Astrophysics::High Energy Astrophysical Phenomena, Milky Way, Dissipative system, Astrophysics, Polarization (waves), Magnetar, Astrophysics::Galaxy Astrophysics
Abstract: Magnetars are the most powerful compact objects in the stellar mass range observed in the Milky Way. Periodicity seen in magnetar persistent emission and also in the temporal tails of powerful giant flares detected from three soft gamma repeaters, and distinctive "spin-down" lengthening of the period have driven the paradigm that strongly-magnetized neutron stars constitute these fascinating sources. The steady X-ray emission includes both thermal atmospheric components and magnetospheric contributions that masquerade as hard X-ray "tails." This paper addresses observational and theoretical elements pertinent to the steady hard X-ray emission of magnetars, focusing on dissipative processes in their magnetospheres, and elements of Comptonization and polarization. It also discusses the action and possible signatures of exotic QED mechanisms like photon splitting and magnetic pair creation, and the quest for their observational vindication.
Published: 2020
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19. The NICER View of the 2020 Burst Storm and Persistent Emission of SGR 1935+2154

Author: Teruaki Enoto, Matthew G. Baring, Zorawar Wadiasingh, Chryssa Kouveliotou, Sebastien Guillot, Beste Begiçarslan, George Younes, Alice K. Harding, Alexander J. van der Horst, Chin-Ping Hu, Ersin Gogus, Walid A. Majid, C. Malacaria, Lin Lin, Tolga Guver, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010504 meteorology & atmospheric sciences, Fast radio burst, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Magnetar, 01 natural sciences, Spectral line, Pulse (physics), Neutron star, Orders of magnitude (time), 13. Climate action, Space and Planetary Science, 0103 physical sciences, Log-normal distribution, Black-body radiation, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract: We report on NICER observations of the Magnetar SGR~1935+2154, covering its 2020 burst storm and long-term persistent emission evolution up to $\sim90$ days post outburst. During the first 1120~seconds taken on April 28 00:40:58 UTC we detect over 217 bursts, corresponding to a burst rate of $>0.2$ bursts s$^{-1}$. Three hours later the rate is at 0.008 bursts s$^{-1}$, remaining at a comparatively low level thereafter. The $T_{90}$ burst duration distribution peaks at 840~ms; the distribution of waiting times to the next burst is fit with a log-normal with an average of 2.1 s. The 1-10 keV burst spectra are well fit by a blackbody, with an average temperature and area of $kT=1.7$ keV and $R^2=53$ km$^2$. The differential burst fluence distribution over $\sim3$ orders of magnitude is well modeled with a power-law form $dN/dF\propto F^{-1.5\pm0.1}$. The source persistent emission pulse profile is double-peaked hours after the burst storm. We find that the bursts peak arrival times follow a uniform distribution in pulse phase, though the fast radio burst associated with the source aligns in phase with the brighter peak. We measure the source spin-down from heavy-cadence observations covering days 21 to 39 post-outburst, $\dot��=-3.72(3)\times10^{-12}$ Hz s$^{-1}$; a factor 2.7 larger than the value measured after the 2014 outburst. Finally, the persistent emission flux and blackbody temperature decrease rapidly in the early stages of the outburst, reaching quiescence 40 days later, while the size of the emitting area remains unchanged., Accepted for publication in the Astrophysical Journal Letters
Published: 2020
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20. Erratum: 'Searches for Gravitational Waves from Known Pulsars at Two Harmonics in 2015–2017 LIGO Data' (2019, ApJ, 879, 10)

Author: P. Kumar, B. R. Hall, R. Cavalieri, A. K. Srivastava, A. E. Pace, A. Fernandez-Galiana, A. Basti, Ryan N. Lang, J.-P. Coulon, T. Hardwick, D. Steinmeyer, E. A. Chase, Z. Frei, Piotr Jaranowski, V. Sequino, S. Caride, Jordan Camp, J. Liu, F. Travasso, Michał Bejger, A. Pasqualetti, J.-D. Fournier, M. Croquette, Philip F. Hopkins, Christian Pedersen, H. M. Lee, L. Xiao, Milan Gupta, P. Fulda, P. T.H. Pang, T. Etzel, G. Mendell, C. S. Unnikrishnan, J. Jiang, I. Fiori, S. J. Jadhav, B. C. Pant, Sourav Ghosh, Imre Bartos, V. Germain, V. Quetschke, Martin M. Fejer, R. Bork, S. Ghonge, Shawn Rosofsky, T. Di Girolamo, K. AultONeal, A. Perreca, S. M. Scott, G. Gemme, L. van der Schaaf, S. A. Pai, Cody Messick, M. Drago, L. E. Wade, Rebecca Fisher, K. S. Phukon, J. Li, J. Eichholz, Guenakh Mitselmakher, Zhihui Du, I. Belahcene, S. E. Barclay, M. Fyffe, R. Kirchhoff, R. Colgan, B. L. Pearlstone, D. M. Macleod, Charalampos Markakis, Archana Pai, W. Z. Korth, Gabriela Gonzalez, K. R. Corley, Christopher P. L. Berry, J. L. Willis, M. Eisenmann, Ofek Birnholtz, Archisman Ghosh, F. Paoletti, B. A. Boom, Samuel Deléglise, B. L. Swinkels, A. M. Sergeev, Torrey Cullen, G. Vedovato, L. E. H. Datrier, Samuele Cortese, Charlie Hoy, A. M. Holgado, G. Ciani, D. B. Kozak, A. D. Silva, J. Suresh, M. C. Milovich-Goff, J. L. Wright, Sebastiano Bernuzzi, P. Booker, S. Mastrogiovanni, Nicolas Sanchis-Gual, P. Ruggi, A. Parida, R. K. Lanza, S. S. Eikenberry, R. Pedurand, Benno Willke, S. T. Countryman, Michael E Zucker, A. Grado, Andrew Matas, C. D. Booth, D. Stocks, Surabhi Sachdev, Christopher J. Moore, Alessandra Corsi, Sanjay Kumar, V. V. Frolov, M. Fitz-Axen, Eric Howell, A. Singhal, P. Thomas, M. Arène, A. Mullavey, T. J. N. Nelson, V. Fafone, J. Betzwieser, C. Vorvick, G. Kang, Daniel E. Holz, B. J. J. Slagmolen, P. Dupej, Alena Ananyeva, Stanislav Babak, M. Constancio, C. Cahillane, Debnandini Mukherjee, C. Pankow, P. M. Meyers, S. Doravari, M. Muratore, M. C. Heintze, P. J. Sutton, Alyssa Garcia, B. Patricelli, F. Carbognani, D. S. Wu, Margaret Millhouse, J. H. Romie, G. D. O'Dea, Bruno Giacomazzo, A. Pal-Singh, S. Leavey, Hai-Ping Cheng, A. Iess, L. K. Nuttall, Erik Katsavounidis, R. Macas, G. Billingsley, S. Macfoy, O. Halim, K. W. Tsang, Kendall Ackley, R. K. Nayak, B. D. Lackey, P. Grassia, Kipp Cannon, M. Steinke, Xiaohui Fan, Richard O'Shaughnessy, B. Barr, J. Worden, Rana X. Adhikari, F. Donovan, R. Kennedy, Geoffrey Lovelace, S. G. Gaonkar, Antoine Heidmann, D. Töyrä, David Jones, Marco Cavaglia, Sascha Husa, G. Venugopalan, D.B. DeBra, A. K. Zadrożny, H. Estelles, K. Siellez, J. Derby, K. A. Thorne, Isabel Cordero-Carrión, Sung-Po Chao, H. Overmier, Eric B. Flynn, B. Gateley, G. Kuehn, Haixing Miao, H. Ohta, G. Bogaert, J. J. Bero, F. J. Raab, N. Mukund, S. Marsat, V. Tiwari, Yann Bouffanais, V. Avendano, Xiuling Li, Matthew Evans, K. L. Dooley, R. Inta, L. R. Cominsky, Rosa Poggiani, V. Frey, A. K. Mehta, S. Farinon, A. Pele, E. J. Daw, Maurizio Canepa, P. H. Nguyen, Antonio Marquina, T. A. Ferreira, M. Rakhmanov, P. Oppermann, Aaron Buikema, J. Hennig, V. Gayathri, S. Walsh, Miriam Cabero, Alessandra Buonanno, R. Metzdorff, C.-J. Haster, Gabrielle Allen, D. M. Wilken, S. Klimenko, Leo Tsukada, P. T. Baker, A. Avila-Alvarez, K. Gill, J. Palfreyman, Fangchen Feng, B. Lantz, B. Irwin, C. C. Yancey, W. G. Anderson, G. Cella, H. Vahlbruch, J. C. Mills, K. Riles, R. Mittleman, Francesco Pannarale, Soichiro Morisaki, Paul J. Groot, M. Zevin, N. A. Holland, K. Rao, Podila Satya Venkata Narasimha Sharma, K. D. Giardina, P. J. Veitch, R. De Rosa, I. Nardecchia, D. Sellers, H. Radkins, Lisa Barsotti, H. Y. Chia, Fl Linde, F. Magaña-Sandoval, M. F. Carney, C. Whittle, R. Gustafson, H. J. Bulten, Anirban Dasgupta, E. Z. Hamilton, Walter Winkler, B. P. Abbott, A. Bozzi, R. J. G. Jonker, J. K. Wofford, M. A. Page, J. Y. Vinet, H. Middleton, J. B. Kanner, Michael Keith, Robert J. McCarthy, C. C. Wipf, E. J. King, Nelson Christensen, Linqing Wen, P. Raffai, L. Naticchioni, Salvatore Vitale, A. Cumming, F. Di Renzo, Lee McCuller, N. Mazumder, J. D. E. Creighton, E. K. Gustafson, M. Weinert, H. A. G. Gabbard, S. V. Angelova, John Veitch, J. Lehmann, T. D. Abbott, J. Meidam, A. W. Heptonstall, Pablo Cerdá-Durán, Vivien Raymond, Peter R. Saulson, Alessandro Corongiu, S. Vass, S. Raja, E. Genin, J. Zhang, F. Baldaccini, L. F. Ortega, A. Rocchi, A. S. Markosyan, S. E. Strigin, J. V. Van Heijningen, H. Fong, G. Greco, J. S. Lange, F. Fidecaro, G. M. Guidi, Harald Lück, F. Marion, J. McIver, Z. Tornasi, M. J. Cowart, P. Puppo, A. L. Urban, D. Ugolini, P. Clearwater, K. E. Ramirez, D. W. Yeeles, Zoheyr Doctor, A. Malik, S. Gaudio, E. J. Fauchon-Jones, R. M. S. Schofield, R. Coyne, Fabrice Matichard, H. N. Isa, N. Arnaud, Maggie Tse, L. Wallace, A. Królak, Riccardo Sturani, J. Hanks, M. Lormand, R. Abbott, A. Ain, R. J. Trudeau, D. Moffa, J. Zweizig, C. De Rossi, D. Verkindt, C. Cocchieri, B. Goncharov, R. Birney, F. Frasconi, E. L. Merilh, M. Kinley-Hanlon, M. C. Tringali, S. Hochheim, N. A. Robertson, M. Cho, David Coward, D. Tuyenbayev, E. A. Huerta, D. J. Stops, J. S. H. Lee, Felix Wellmann, R. Flaminio, J. Warner, J. J. McCann, T. J. Slaven-Blair, S. ShyamSundar, C. Stachie, R. Frey, Duncan Meacher, N. V. Keerthana, Moritz Mehmet, Benjamin J. Owen, R. Passaquieti, J. F. J. van den Brand, E. A. Muñiz, K. Y. Ng, S. Brunett, Marco Romanelli, E. K. Wessel, Vijay Varma, M. MacInnis, C. Rajan, J. K. Blackburn, Bala R. Iyer, Terry G. McRae, E. Chassande-Mottin, S. P. Stevenson, Sebastian Steinlechner, Sheila Rowan, S. Caudill, G. Gaur, S. C. McGuire, J. F. Read, Chris A. Collins, J. G. Bartlett, Márton Tápai, W. Ren, Mandar Patil, Abhirup Ghosh, Sheon Chua, S. Sunil, M. Tacca, Martin Hendry, Cecilio García-Quirós, R. Bonnand, S. Di Pace, Mariana Fazio, A. Dmitriev, G. Koekoek, A. J. Weinstein, R. Goetz, S. Katsanevas, V. Boschi, Marcus E. Lower, Tarun Souradeep, M. Yvert, S. Ponrathnam, B. U. Gadre, M. Pürrer, S. Kwang, C. L. Romel, M. C. Díaz, Sebastien Biscans, G. A. Prodi, J. C. Barayoga, S. McCormick, P. Rapagnani, T. Mistry, A. L. Stuver, D. Hoak, D. Sentenac, A. Bisht, R. DeSalvo, Karsten Danzmann, N. Letendre, L. G. Prokhorov, Patrick Brady, Nikhil Sarin, D. Passuello, Odylio D. Aguiar, I. W. Martin, C. F. Da Silva Costa, Hua Wang, M. van Beuzekom, Liam Cunningham, M. Punturo, Leopoldo Milano, K. Haris, Madeline Wade, M. Di Giovanni, P. Leaci, L. Glover, S. A. Bilgili, Jay D. Tasson, S. Mitra, A. W. Jones, H. S. Chen, M. Landry, R. De Pietri, S. Biscoveanu, Rocco Romano, A. Cirone, P. Couvares, F. Garufi, David H. Shoemaker, S. Karki, Junwei Cao, O. V. Palashov, Sean T. McWilliams, Y. Boetzel, Hongyu Shen, Nicholas Demos, J. D. Lough, D. C. Coyne, Colm Talbot, Andreas Freise, M. Boer, M. A. Okada, Shubhanshu Tiwari, A. F. Brooks, P. J. Quinonez, F. Piergiovanni, Slawomir Gras, D. Lumaca, M. Haney, K. Mason, L. Di Fiore, B. 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Astrophysics Laboratory, Columbia University, New York, Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Osservatorio Astronomico di Cagliari, Astrochemistry Group (INAF), Hakubi Center, Max-Planck-Institut für Radioastronomie at Effelsberg, CRESST/NASA GSFC, Astrophysics Science Division, Jodrell Bank Centre for Astrophysics (JBCA), Space Science Division (NRL-SSD), Department of Physical Sciences, University of Tasmania, Private Bag 37, Hobart, Tasmania 7001, Australia, Laboratoire Univers et Théories (LUTH (UMR_8102)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Abbott, Bp, Abbott, R, Abbott, Td, Abraham, S, Acernese, F, Ackley, K, Adams, C, Adhikari, Rx, Adya, Vb, Affeldt, C, Agathos, M, Agatsuma, K, Aggarwal, N, Aguiar, Od, Aiello, L, Ain, A, Ajith, P, Allen, G, Allocca, A, Aloy, Ma, Altin, Pa, Amato, A, Anand, S, Ananyeva, A, Anderson, Sb, Anderson, Wg, Angelova, Sv, Antier, S, Appert, S, Arai, K, Araya, Mc, Areeda, J, Arene, M, Arnaud, N, Aronson, Sm, Ascenzi, S, Ashton, G, Aston, Sm, Astone, P, Aubin, F, Aufmuth, P, Aultoneal, K, Austin, C, Avendano, V, Avila-Alvarez, A, Babak, S, Bacon, P, Badaracco, F, Bader, Mkm, Bae, S, Baird, J, Baker, Pt, Baldaccini, F, Ballardin, G, Ballmer, Sw, Bals, A, Banagiri, S, Barayoga, Jc, Barbieri, C, Barclay, Se, Barish, Bc, Barker, D, Barkett, K, Barnum, S, Barone, F, Barr, B, Barsotti, L, Barsuglia, M, Barta, D, Bartlett, J, Bartos, I, Bassiri, R, Basti, A, Bawaj, M, Bayley, Jc, Bazzan, M, Becsy, B, Bejger, M, Belahcene, I, Bell, A, Beniwal, D, Benjamin, Mg, Berger, Bk, Bergmann, G, Bernuzzi, S, Berry, Cpl, Bersanetti, D, Bertolini, A, Betzwieser, J, Bhandare, R, Bidler, J, Biggs, E, Bilenko, Ia, Bilgili, Sa, Billingsley, G, Birney, R, Birnholtz, O, Biscans, S, Bischi, M, Biscoveanu, S, Bisht, A, Bitossi, M, Bizouard, Ma, Blackburn, Jk, Blackman, J, Blair, Cd, Blair, Dg, Blair, Rm, Bloemen, S, Bobba, F, Bode, N, Boer, M, Boetzel, Y, Bogaert, G, Bondu, F, Bonnand, R, Booker, P, Boom, Ba, Bork, R, Boschi, V, Bose, S, Bossilkov, V, Bosveld, J, Bouffanais, Y, Bozzi, A, Bradaschia, C, Brady, Pr, Bramley, A, Branchesi, M, Brau, Je, Breschi, M, Briant, T, Briggs, Jh, Brighenti, F, Brillet, A, Brinkmann, M, Brockill, P, Brooks, Af, Brooks, J, Brown, Dd, Brunett, S, Buikema, A, Bulik, T, Bulten, Hj, Buonanno, A, Buskulic, D, Buy, C, Byer, Rl, Cabero, M, Cadonati, L, Cagnoli, G, Cahillane, C, Bustillo, Jc, Callister, Ta, Calloni, E, Camp, Jb, Campbell, Wa, Cannon, Kc, Cao, H, Cao, J, Carapella, G, Carbognani, F, Caride, S, Carney, Mf, Carullo, G, Diaz, Jc, Casentini, C, Caudill, S, Cavaglia, M, Cavalier, F, Cavalieri, R, Cella, G, Cerda-Duran, P, Cesarini, E, Chaibi, O, Chakravarti, K, Chamberlin, Sj, Chan, M, Chao, S, Charlton, P, Chase, Ea, Chassande-Mottin, E, Chatterjee, D, Chaturvedi, M, Cheeseboro, Bd, Chen, Hy, Chen, X, Chen, Y, Cheng, Hp, Cheong, Ck, Chia, Hy, Chiadini, F, Chincarini, A, Chiummo, A, Cho, G, Cho, H, Cho, M, Christensen, N, Chu, Q, Chua, S, Chung, Kw, Chung, S, Ciani, G, Cieslar, M, Ciobanu, Aa, Ciolfi, R, Cipriano, F, Cirone, A, Clara, F, Clark, Ja, Clearwater, P, Cleva, F, Coccia, E, Cohadon, Pf, Cohen, D, Colleoni, M, Collette, Cg, Collins, C, Colpi, M, Cominsky, Lr, Constancio, M, Conti, L, Cooper, Sj, Corban, P, Corbitt, Tr, Cordero-Carrion, I, Corezzi, S, Corley, Kr, Cornish, N, Corre, D, Corsi, A, Cortese, S, Costa, Ca, Cotesta, R, Coughlin, Mw, Coughlin, Sb, Coulon, Jp, Countryman, St, Couvares, P, Covas, Pb, Cowan, Ee, Coward, Dm, Cowart, Mj, Coyne, Dc, Coyne, R, Creighton, Jde, Creighton, Td, Cripe, J, Croquette, M, Crowder, Sg, Cullen, Tj, Cumming, A, Cunningham, L, Cuoco, E, Dal Canton, T, Dalya, G, D'Angelo, B, Danilishin, Sl, D'Antonio, S, Danzmann, K, Dasgupta, A, Costa, Cfd, Datrier, Leh, Dattilo, V, Dave, I, Davier, M, Davis, D, Daw, Ej, Debra, D, Deenadayalan, M, Degallaix, J, De Laurentis, M, Deleglise, S, Del Pozzo, W, Demarchi, Lm, Demos, N, Dent, T, De Pietri, R, De Rosa, R, De Rossi, C, Desalvo, R, de Varona, O, Dhurandhar, S, Diaz, Mc, Dietrich, T, Di Fiore, L, Difronzo, C, Di Giorgio, C, Di Giovanni, F, Di Giovanni, M, Di Girolamo, T, Di Lieto, A, Ding, B, Di Pace, S, Di Palma, I, Di Renzo, F, Divakarla, Ak, Dmitriev, A, Doctor, Z, Donovan, F, Dooley, Kl, Doravari, S, Dorrington, I, Downes, Tp, Drago, M, Driggers, Jc, Du, Z, Ducoin, Jg, Dupej, P, Durante, O, Dwyer, Se, Easter, Pj, Eddolls, G, Edo, Tb, Effler, A, Ehrens, P, Eichholz, J, Eikenberry, S, Eisenmann, M, Eisenstein, Ra, Errico, L, Essick, Rc, Estelles, H, Estevez, D, Etienne, Zb, Etzel, T, Evans, M, Evans, Tm, Fafone, V, Fairhurst, S, Fan, X, Farinon, S, Farr, B, Farr, Wm, Fauchon-Jones, Ej, Favata, M, Fays, M, Fazio, M, Fee, C, Feicht, J, Fejer, Mm, Feng, F, Fernandez-Galiana, A, Ferrante, I, Ferreira, Ec, Ferreira, Ta, Fidecaro, F, Fiori, I, Fiorucci, D, Fishbach, M, Fisher, Rp, Fishner, Jm, Fittipaldi, R, Fitz-Axen, M, Fiumara, V, Flaminio, R, Fletcher, M, Floden, E, Flynn, E, Fong, H, Font, Ja, Forsyth, Pwf, Fournier, Jd, Vivanco, Fh, Frasca, S, Frasconi, F, Frei, Z, Freise, A, Frey, R, Frey, V, Fritschel, P, Frolov, Vv, Fronze, G, Fulda, P, Fyffe, M, Gabbard, Ha, Gadre, Bu, Gaebel, Sm, Gair, Jr, Gammaitoni, L, Gaonkar, Sg, Garcia-Quiros, C, Garufi, F, Gateley, B, Gaudio, S, Gaur, G, Gayathri, V, Gemme, G, Genin, E, Gennai, A, George, D, George, J, Gergely, L, Ghonge, S, Ghosh, A, Ghosh, S, Giacomazzo, B, Giaime, Ja, Giardina, Kd, Gibson, Dr, Gill, K, Glover, L, Gniesmer, J, Godwin, P, Goetz, E, Goetz, R, Goncharov, B, Gonzalez, G, Castro, Jmg, Gopakumar, A, Gossan, Se, Gosselin, M, Gouaty, R, Grace, B, Grado, A, Granata, M, Grant, A, Gras, S, Grassia, P, Gray, C, Gray, R, Greco, G, Green, Ac, Green, R, Gretarsson, Em, Grimaldi, A, Grimm, Sj, Groot, P, Grote, H, Grunewald, S, Gruning, P, Guidi, Gm, Gulati, Hk, Guo, Y, Gupta, A, Gupta, P, Gustafson, Ek, Gustafson, R, Haegel, L, Halim, O, Hall, Br, Hall, Ed, Hamilton, Ez, Hammond, G, Haney, M, Hanke, Mm, Hanks, J, Hanna, C, Hannuksela, Oa, Hansen, Tj, Hanson, J, Harder, T, Hardwick, T, Haris, K, Harms, J, Harry, Gm, Harry, Iw, Hasskew, Rk, Haster, Cj, Haughian, K, Hayes, Fj, Healy, J, Heidmann, A, Heintze, Mc, Heitmann, H, Hellman, F, Hello, P, Hemming, G, Hendry, M, Heng, I, Hennig, J, Heurs, M, Hild, S, Hinderer, T, Hochheim, S, Hofman, D, Holgado, Am, Holland, Na, Holt, K, Holz, De, Hopkins, P, Horst, C, Hough, J, Howell, Ej, Hoy, Cg, Huang, Y, Hubner, Mt, Huerta, Ea, Huet, D, Hughey, B, Hui, V, Husa, S, Huttner, Sh, Huynh-Dinh, T, Idzkowski, B, Iess, A, Inchauspe, H, Ingram, C, Inta, R, Intini, G, Irwin, B, Isa, Hn, Isac, Jm, Isi, M, Iyer, Br, Jacqmin, T, Jadhav, Sj, Jani, K, Janthalur, Nn, Jaranowski, P, Jariwala, D, Jenkins, Ac, Jiang, J, Johnson, D, Jones, Aw, Jones, Di, Jones, Jd, Jones, R, Jonker, Rjg, Ju, L, Junker, J, Kalaghatgi, Cv, Kalogera, V, Kamai, B, Kandhasamy, S, Kang, G, Kanner, Jb, Kapadia, Sj, Karki, S, Kashyap, R, Kasprzack, M, Katsanevas, S, Katsavounidis, E, Katzman, W, Kaufer, S, Kawabe, K, Keerthana, Nv, Kefelian, F, Keitel, D, Kennedy, R, Key, J, Khalili, Fy, Khan, I, Khan, S, Khazanov, Ea, Khetan, N, Khursheed, M, Kijbunchoo, N, Kim, C, Kim, Jc, Kim, K, Kim, W, Kim, Ym, Kimball, C, King, Pj, Kinley-Hanlon, M, Kirchhoff, R, Kissel, J, Kleybolte, L, Klika, Jh, Klimenko, S, Knowles, Td, Koch, P, Koehlenbeck, Sm, Koekoek, G, Koley, S, Kondrashov, V, Kontos, A, Koper, N, Korobko, M, Korth, Wz, Kovalam, M, Kozak, Db, Kramer, C, Kringel, V, Krishnendu, N, Krolak, A, Krupinski, N, Kuehn, G, Kumar, A, Kumar, P, Kumar, R, Kuo, L, Kutynia, A, Kwang, S, Lackey, Bd, Laghi, D, Lai, Kh, Lam, Tl, Landry, M, Lane, Bb, Lang, Rn, Lange, J, Lantz, B, Lanza, Rk, Lartaux-Vollard, A, Lasky, Pd, Laxen, M, Lazzarini, A, Lazzaro, C, Leaci, P, Leavey, S, Lecoeuche, K, Lee, Ch, Lee, Hk, Lee, Hm, Lee, Hw, Lee, J, Lee, K, Lehmann, J, Lenon, Ak, Leroy, N, Letendre, N, Levin, Y, Li, A, Li, J, Li, Kjl, Li, Tgf, Li, X, Lin, F, Linde, F, Linker, Sd, Littenberg, Tb, Liu, J, Liu, X, Llorens-Monteagudo, M, Lo, Rkl, London, Lt, Longo, A, Lorenzini, M, Loriette, V, Lormand, M, Losurdo, G, Lough, Jd, Lousto, Co, Lovelace, G, Lower, Me, Luck, H, Lumaca, D, Lundgren, Ap, Lynch, R, Ma, Y, Macas, R, Macfoy, S, Macinnis, M, Macleod, Dm, Macquet, A, Hernandez, Im, Magana-Sandoval, F, Magee, Rm, Majorana, E, Maksimovic, I, Malik, A, Man, N, Mandic, V, Mangano, V, Mansell, Gl, Manske, M, Mantovani, M, Mapelli, M, Marchesoni, F, Marion, F, Marka, S, Marka, Z, Markakis, C, Markosyan, A, Markowitz, A, Maros, E, Marquina, A, Marsat, S, Martelli, F, Martin, Iw, Martin, Rm, Martinez, V, Martynov, Dv, Masalehdan, H, Mason, K, Massera, E, Masserot, A, Massinger, Tj, Masso-Reid, M, Mastrogiovanni, S, Matas, A, Matichard, F, Matone, L, Mavalvala, N, Mccann, Jj, Mccarthy, R, Mcclelland, De, Mccormick, S, Mcculler, L, Mcguire, Sc, Mcisaac, C, Mciver, J, Mcmanus, Dj, Mcrae, T, Mcwilliams, St, Meacher, D, Meadors, Gd, Mehmet, M, Mehta, Ak, Meidam, J, Villa, Em, Melatos, A, Mendell, G, Mercer, Ra, Mereni, L, Merfeld, K, Merilh, El, Merzougui, M, Meshkov, S, Messenger, C, Messick, C, Messina, F, Metzdorff, R, Meyers, Pm, Meylahn, F, Miani, A, Miao, H, Michel, C, Middleton, H, Milano, L, Miller, L, Millhouse, M, Mills, Jc, Milovich-Goff, Mc, Minazzoli, O, Minenkov, Y, Mishkin, A, Mishra, C, Mistry, T, Mitra, S, Mitrofanov, Vp, Mitselmakher, G, Mittleman, R, Mo, G, Moffa, D, Mogushi, K, Mohapatra, Srp, Molina-Ruiz, M, Mondin, M, Montani, M, Moore, Cj, Moraru, D, Morawski, F, Moreno, G, Morisaki, S, Mours, B, Mow-Lowry, M, Muciaccia, F, Mukherjee, A, Mukherjee, D, Mukherjee, S, Mukund, N, Mullavey, A, Munch, J, Muniz, Ea, Muratore, M, Murray, Pg, Nagar, A, Nardecchia, I, Naticchioni, L, Nayak, Rk, Neil, Bf, Neilson, J, Nelemans, G, Nelson, Tjn, Nery, M, Neunzert, A, Nevin, L, Ng, Ky, Ng, S, Nguyen, C, Nguyen, P, Nichols, D, Nichols, Sa, Nissanke, S, Nocera, F, North, C, Nuttall, Lk, Obergaulinger, M, Oberling, J, O'Brien, Bd, Oganesyan, G, Ogin, Gh, Oh, Jj, Oh, Sh, Ohme, F, Ohta, H, Okada, Ma, Oliver, M, Oppermann, P, Oram, Rj, O'Reilly, B, Ormiston, Rg, Ortega, Lf, O'Shaughnessy, R, Ossokine, S, Ottaway, Dj, Overmier, H, Owen, Bj, Pace, Ae, Pagano, G, Page, Ma, Pagliaroli, G, Pai, A, Pai, Sa, Palamos, Jr, Palashov, O, Palomba, C, Pan, H, Panda, Pk, Pang, Pth, Pankow, C, Pannarale, F, Pant, Bc, Paoletti, F, Paoli, A, Parida, A, Parker, W, Pascucci, D, Pasqualetti, A, Passaquieti, R, Passuello, D, Patil, M, Patricelli, B, Payne, E, Pearlstone, Bl, Pechsiri, Tc, Pedersen, Aj, Pedraza, M, Pedurand, R, Pele, A, Penn, S, Perego, A, Perez, Cj, Perigois, C, Perreca, A, Petermann, J, Pfeiffer, Hp, Phelps, M, Phukon, K, Piccinni, Oj, Pichot, M, Piergiovanni, F, Pierro, V, Pillant, G, Pinard, L, Pinto, Im, Pirello, M, Pitkin, M, Plastino, W, Pong, Dyt, Ponrathnam, S, Popolizio, P, Porter, Ek, Powell, J, Prajapati, Ak, Prasad, J, Prasai, K, Prasanna, R, Pratten, G, Prestegard, T, Principe, M, Prodi, Ga, Prokhorov, L, Punturo, M, Puppo, P, Purrer, M, Qi, H, Quetschke, V, Quinonez, Pj, Raab, Fj, Raaijmakers, G, Radkins, H, Radulesco, N, Raffai, P, Raja, S, Rajan, C, Rajbhandari, B, Rakhmanov, M, Ramirez, Ke, Ramos-Buades, A, Rana, J, Rao, K, Rapagnani, P, Raymond, V, Razzano, M, Read, J, Regimbau, T, Rei, L, Reid, S, Reitze, Dh, Rettegno, P, Ricci, F, Richardson, Cj, Richardson, Jw, Ricker, Pm, Riemenschneider, G, Riles, K, Rizzo, M, Robertson, Na, Robinet, F, Rocchi, A, Rolland, L, Rollins, Jg, Roma, Vj, Romanelli, M, Romano, R, Romel, Cl, Romie, Jh, Rose, Ca, Rose, D, Rose, K, Rosinska, D, Rosofsky, Sg, Ross, Mp, Rowan, S, Rudiger, A, Ruggi, P, Rutins, G, Ryan, K, Sachdev, S, Sadecki, T, Sakellariadou, M, Salafia, O, Salconi, L, Saleem, M, Samajdar, A, Sammut, L, Sanchez, Ej, Sanchez, Le, Sanchis-Gual, N, Sanders, Jr, Santiago, Ka, Santos, E, Sarin, N, Sassolas, B, Saulson, Pr, Sauter, O, Savage, Rl, Schale, P, Scheel, M, Scheuer, J, Schmidt, P, Schnabel, R, Schofield, Rm, Schonbeck, A, Schreiber, E, Schulte, Bw, Schutz, Bf, Scott, J, Scott, Sm, Seidel, E, Sellers, D, Sengupta, A, Sennett, N, Sentenac, D, Sequino, V, Sergeev, A, Setyawati, Y, Shaddock, Da, Shaffer, T, Shahriar, M, Shaner, Mb, Sharma, A, Sharma, P, Shawhan, P, Shen, H, Shink, R, Shoemaker, Dh, Shoemaker, Dm, Shukla, K, Shyamsundar, S, Siellez, K, Sieniawska, M, Sigg, D, Singer, Lp, Singh, D, Singh, N, Singhal, A, Sintes, Am, Sitmukhambetov, S, Skliris, V, Slagmolen, Bjj, Slaven-Blair, Tj, Smith, Jr, Smith, Rje, Somala, S, Son, Ej, Soni, S, Sorazu, B, Sorrentino, F, Souradeep, T, Sowell, E, Spencer, Ap, Spera, M, Srivastava, Ak, Srivastava, V, Staats, K, Stachie, C, Standke, M, Steer, Da, Steinke, M, Steinlechner, J, Steinlechner, S, Steinmeyer, D, Stevenson, Sp, Stocks, D, Stone, R, Stops, Dj, Strain, Ka, Stratta, G, Strigin, Se, Strunk, A, Sturani, R, Stuver, Al, Sudhir, V, Summerscales, Tz, Sun, L, Sunil, S, Sur, A, Suresh, J, Sutton, Pj, Swinkels, Bl, Szczepanczyk, Mj, Tacca, M, Tait, Sc, Talbot, C, Tanner, Db, Tao, D, Tapai, M, Tapia, A, Tasson, Jd, Taylor, R, Tenorio, R, Terkowski, L, Thomas, M, Thomas, P, Thondapu, Sr, Thorne, Ka, Thrane, E, Tiwari, S, Tiwari, V, Toland, K, Tonelli, M, Tornasi, Z, Torres-Forne, A, Torrie, Ci, Toyra, D, Travasso, F, Traylor, G, Tringali, Mc, Tripathee, A, Trovato, A, Trozzo, L, Tsang, Kw, Tse, M, Tso, R, Tsukada, L, Tsuna, D, Tsutsui, T, Tuyenbayev, D, Ueno, K, Ugolini, D, Unnikrishnan, C, Urban, Al, Usman, Sa, Vahlbruch, H, Vajente, G, Valdes, G, Valentini, M, van Bakel, N, van Beuzekom, M, van den Brand, Jfj, Van Den Broeck, C, Vander-Hyde, Dc, van der Schaaf, L, Vanheijningen, Jv, van Veggel, Aa, Vardaro, M, Varma, V, Vass, S, Vasuth, M, Vecchio, A, Vedovato, G, Veitch, J, Veitch, Pj, Venkateswara, K, Venugopalan, G, Verkindt, D, Vetrano, F, Vicere, A, Viets, Ad, Vinciguerra, S, Vine, Dj, Vinet, Jy, Vitale, S, Vo, T, Vocca, H, Vorvick, C, Vyatchanin, Sp, Wade, Ar, Wade, Le, Wade, M, Walet, R, Walker, M, Wallace, L, Walsh, S, Wang, H, Wang, Jz, Wang, S, Wang, Wh, Wang, Yf, Ward, Rl, Warden, Za, Warner, J, Was, M, Watchi, J, Weaver, B, Wei, Lw, Weinert, M, Weinstein, Aj, Weiss, R, Wellmann, F, Wen, L, Wessel, K, Wessels, P, Westhouse, Jw, Wette, K, Whelan, Jt, Whiting, Bf, Whittle, C, Wilken, Dm, Williams, D, Williamson, Ar, Willis, Jl, Willke, B, Winkler, W, Wipf, Cc, Wittel, H, Woan, G, Woehler, J, Wofford, Jk, Wright, Jl, Wu, D, Wysocki, Dm, Xiao, S, Xu, R, Yamamoto, H, Yancey, Cc, Yang, L, Yang, Y, Yang, Z, Yap, Mj, Yazback, M, Yeeles, Dw, Yu, H, Yu, Hc, Yuen, Shr, Zadrozny, Ak, Zadrozny, A, Zanolin, M, Zelenova, T, Zendri, Jp, Zevin, M, Zhang, J, Zhang, L, Zhang, T, Zhao, C, Zhao, G, Zhou, M, Zhou, Z, Zhu, Xj, Zimmerman, Ab, Zucker, Me, Zweizig, J, (Astro)-Particles Physics, Arzoumanian, Z, Bogdanov, S, Cognard, I, Corongiu, A, Enoto, T, Freire, P, Gendreau, Kc, Guillemot, L, Harding, Ak, Jankowski, F, Keith, Mj, Kerr, M, Lyne, A, Palfreyman, J, Possenti, A, Ridolfi, A, Stappers, B, Theureau, G, Weltervrede, P, Université de Lyon-Université de Lyon-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon, Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)
Subjects: Known Pulsars, 010504 meteorology & atmospheric sciences, Astronomy, Astrophysics, Table (information), Vela, gravitational waves, pulsars, 01 natural sciences, Pulsar, 0103 physical sciences, Limit (mathematics), 010303 astronomy & astrophysics, gravitational wave, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Physics, [PHYS]Physics [physics], Gravitational wave, Two Harmonics, Astronomy and Astrophysics, Gravitational Waves, Known Pulsars, Two Harmonics, Erratum, LIGO, Amplitude, Space and Planetary Science, Erratum, Glitch (astronomy), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Two analysis errors have been identified that affect the results for a handful of the high-value pulsars given in Table 1 of Abbott et al. (2019). One affects the Bayesian analysis for the five pulsars that glitched during the analysis period, and the other affects the 5n-vector analysis for J0711-6830. Updated results after correcting the errors are shown in Table 1, which now supersedes the results given for those pulsars in Table 1 of Abbott et al. (2019). Updated versions of figures can be seen in Figures 1-4. Bayesian analysis.-For the glitching pulsars, the signal phase evolution caused by the glitch was wrongly applied twice and was therefore not consistent with our expected model of the pulsar phase. This error did not affect the F/G-statistic or 5n-vector analysis. Analyses of the five pulsars PSR J0205+6449, PSR J0534+2200, PSR J0835-4510, PSR J1028-5819, and PSR J1718-3825 have been repeated after correcting for the error. There are small quantitative differences in the results, but the changes do not affect the main conclusions of the paper. The largest differences are for PSR J0835-4510 (the Vela pulsar), for which the updated upper limits from the Bayesian method are found to be between 1.1 and 2 times larger than those obtained when the error was present. This appears primarily to be due to the error leading to the decohering of a strong spectral line in the LIGO Livingston detector and thus lowering the amplitude limit. 5n-vector analysis.-An error was also identified in the settings of the 5n-vector analysis, which affected the upper limit computation at the rotation frequency for C21 95% of J0711-6830. Specifically, we found an incorrect choice for the range of amplitudes used to inject simulated signals in the O2 data. The updated upper limit is about 2.5 times worse than that obtained when the error was present. This error did not affect the Bayesian or F/G-statistic results. (Table Presented) (Figure Presented).
Published: 2020
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21. Plasma Fluctuations Could Generate Bright Pulsar Emission

Author: Alice K. Harding
Subjects: Physics, Pulsar, Astrophysics, Plasma
Published: 2020
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22. A NICER View of Spectral and Profile Evolution for Three X-ray Emitting Millisecond Pulsars

Author: Zaven Arzoumanian, Lauren Lugo, Paul S. Ray, Slavko Bogdanov, Julia Deneva, Scott M. Ransom, Matthew Kerr, Elizabeth Spano, Keith C. Gendreau, Christo Venter, Andrea N. Lommen, Sebastien Guillot, Kent S. Wood, Natalia Lewandowska, D. M. Rowan, Craig B. Markwardt, Alice K. Harding, Renee M. Ludlam, Zaynab Ghazi, Teruaki Enoto, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), and 12006653 - Venter, Christo
Subjects: 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Context (language use), Astrophysics, 7. Clean energy, 01 natural sciences, Neutron stars, X-ray astronomy, Pulsar, Millisecond pulsar, 0103 physical sciences, Emission spectrum, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Millisecond pulsars, Neutron Star Interior Composition Explorer, Astronomy and Astrophysics, Pulse (physics), Neutron star, 13. Climate action, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: We present two years of Neutron star Interior Composition Explorer (NICER) X-ray observations of three energetic rotation-powered millisecond pulsars (MSPs): PSRs B1937+21, B1821-24, and J0218+4232. We fit Gaussians and Lorentzians to the pulse profiles for different energy sub-bands of the soft X-ray regime to measure the energy dependence of pulse separation and width. We find that the separation between pulse components of PSR J0218+4232 decreases with increasing energy at $\gt 3\sigma$ confidence. The 95% upper limit on pulse separation evolution for PSRs B1937+21 and B1821-24 is less than 2 milliperiods per keV. Our phase-resolved spectral results provide updated constraints on the non-thermal X-ray emission of these three pulsars. The photon indices of the modeled X-ray emission spectra for each pulse component of PSR B1937+21 are inconsistent with each other at the 90% confidence level, suggesting different emission origins for each pulse. We find that the PSR B1821-24 and PSR J0218+4232 emission spectra are invariant with phase at the 90% confidence level. We describe the implications of our profile and spectral results in the context of equatorial current sheet emission models for these three MSPs with non-thermal, magnetospheric X-ray emission., Comment: 16 pages, 13 figures, accepted for publication in ApJ
Published: 2020
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23. Exploiting morphological data from Pulsar Wind Nebulae via a spatiotemporal leptonic transport code

Author: Christo Venter, A. S. Seyffert, Alice K. Harding, C. van Rensburg, 21106266 - Van Rensburg, Carlo, 12006653 - Venter, Christo, and 20126999 - Seyffert, Albertus Stefanus
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Astroparticle physics, Physics, general [Gamma-rays], non-thermal [Radiation mechanisms], numerical [Methods], Astrophysics::High Energy Astrophysical Phenomena, supernova remnants [ISM], FOS: Physical sciences, Astronomy and Astrophysics, Radius, Astrophysics, law.invention, Telescope, Pulsar, Space and Planetary Science, law, Test statistic, Spectral energy distribution, Surface brightness, Astrophysics - High Energy Astrophysical Phenomena, Cherenkov radiation
Abstract: The next era of ground-based Cherenkov telescope development will see a great increase in both quantity and quality of $\gamma$-ray morphological data. This initiated the development of a spatio-temporal leptonic transport code to model pulsar wind nebulae. We present results from this code that predicts the evolution of the leptonic particle spectrum and radiation at different radii in a spherically-symmetric source. We simultaneously fit the overall broadband spectral energy distribution, the surface brightness profile and the X-ray photon index vs.\ radius for PWN 3C~58, PWN G21.5$-$0.9 and PWN G0.9+0.1. Such concurrent fitting of disparate data sets is non-trivial and we thus investigate the utility of different goodness-of-fit statistics, specifically the traditional $\chi^2$ test statistic and a newly developed scaled-flux-normalised test statistic to obtain best-fit parameters. We find reasonable fits to the spatial and spectral data of all three sources, but note some remaining degeneracies that will have to be broken by future observations., Comment: 13 Pages, 13 Figures. 4 Tables
Published: 2020

24. A NICER View of PSR J0030+0451: Evidence for a Global-scale Multipolar Magnetic Field

Author: Alice K. Harding, Slavko Bogdanov, Deepto Chakrabarty, Zaven Arzoumanian, Paul S. Ray, Thomas E. Riley, Anna V. Bilous, Anna L. Watts, Wynn C. G. Ho, Keith C. Gendreau, Sebastien Guillot, High Energy Astrophys. & Astropart. Phys (API, FNWI), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Neutron Star Interior Composition Explorer, 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Antipodal point, Magnetosphere, Astronomy and Astrophysics, Astrophysics, 16. Peace & justice, 01 natural sciences, Magnetic field, Neutron star, Dipole, Astrophysics - Solar and Stellar Astrophysics, Pulsar, Space and Planetary Science, Millisecond pulsar, 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences
Abstract: Recent modeling of NICER observations of thermal X-ray pulsations from the surface of the isolated millisecond pulsar PSR J0030+0451 suggests that the hot emitting regions on the pulsar's surface are far from antipodal, which is at odds with the classical assumption that the magnetic field in the pulsar magnetosphere is predominantly that of a centered dipole. Here, we review these results and examine previous attempts to constrain the magnetospheric configuration of PSR J0030+0451. To the best of our knowledge, there is in fact no direct observational evidence that PSR J0030+0451's magnetic field is a centered dipole. Developing models of physically motivated, non-canonical magnetic field configurations and the currents that they can support poses a challenging task. However, such models may have profound implications for many aspects of pulsar research, including pulsar braking, estimates of birth velocities, and interpretations of multi-wavelength magnetospheric emission., Comment: Appears in ApJ Letters Focus Issue on NICER Constraints on the Dense Matter Equation of State
Published: 2019
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25. Hard Spectral Tails in Magnetars

Author: Matthew G. Baring, Peter L. Gonthier, Zorawar Wadiasingh, and Alice K. Harding
Subjects: Physics, Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, Astronomy and Astrophysics, Astrophysics, Magnetar
Abstract: Pulsed non-thermal quiescent emission between 10 keV and around 150 keV has been observed in ~10 magnetars. For inner magnetospheric models of such hard X-ray signals, resonant Compton upscattering of soft thermal photons from the neutron star surface is the most efficient radiative process. We present angle-dependent hard X-ray upscattering model spectra for uncooled monoenergetic relativistic electrons. The spectral cut-off energies are critically dependent on the observer viewing angles and electron Lorentz factor. We find that electrons with energies less than around 15 MeV will emit most of their radiation below 250 keV, consistent with the observed turnovers in magnetar hard X-ray tails. Moreover, electrons of higher energy still emit most of the radiation below around 1 MeV, except for quasi-equatorial emission locales for select pulses phases. Our spectral computations use new state-of-the-art, spin-dependent formalism for the QED Compton scattering cross section in strong magnetic fields.
Published: 2017
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26. Modelling the polarisation signatures detected from the first white dwarf pulsar AR Sco

Author: Zorawar Wadiasingh, Louis du Plessis, Christo Venter, Alice K. Harding, Pieter Meintjes, S. Chandra, 31125417 - Chandra, Sunil, 26594080 - Wadiasingh, Zorawar, 12006653 - Venter, Christo, and 25936328 - Du Plessis, Louis
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Magnetic dip, White dwarf, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Orbital period, Position angle, Pulsar, Phase angle (astronomy), Polar, Astrophysics::Solar and Stellar Astrophysics, Binary system, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics::Galaxy Astrophysics
Abstract: Marsh et al. detected radio and optical pulsations from the binary system AR Scorpii (AR Sco). This system, with an orbital period of 3.56 h, is composed of a cool, low-mass star and a white dwarf with a spin period of 1.95 min. Optical observations by Buckley et al. showed that the polarimetric emission from the white dwarf is strongly linearly polarised ( up to $\sim40\%$) with periodically changing intensities. This periodic non-thermal emission is thought to be powered by the highly magnetised ($ 5 \times 10^{8} $ G) white dwarf that is spinning down. The morphology of the polarisation signal, namely the position angle plotted against the phase angle, is similar to that seen in many radio pulsars. In this paper, we demonstrate that we can fit the traditional pulsar rotating vector model to the optical position angle. We used a Markov-chain-Monte-Carlo technique to find the best fit for the model yielding a magnetic inclination angle of $\alpha = (86.6^{+3.0}_{-2.8})^{\circ}$ and an observer angle of $\zeta = (60.5^{+5.3}_{-6.1})^{\circ}$. This modelling supports the scenario that the synchrotron emission originates above the polar caps of the white dwarf pulsar and that the latter is an orthogonal rotator., Comment: 6 pages, 2 figures, HEASA 2018 proceedings of science
Published: 2019

27. Probing the pulsar population of Terzan 5 via spectral modeling

Author: A. Kopp, D. J. van der Walt, Peter Eger, Alice K. Harding, Tyrel J. Johnson, David A. Smith, Christo Venter, Hambeleleni Ndiyavala, Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), 24483818 - Kopp, Andreas, 10060499 - Van der Walt, Diederick Johannes, 12006653 - Venter, Christo, and 26403366 - Ndiyavala, Hambeleleni
Subjects: Physics, High Energy Astrophysical Phenomena (astro-ph.HE), education.field_of_study, non-thermal [Radiation mechanisms], 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Population, general [Pulsars], FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Pulsar, Space and Planetary Science, 0103 physical sciences, individual (Terzan 5) [Globular clusters], education, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics
Abstract: Terzan 5 is the only Galactic globular cluster that has plausibly been detected at very-high energies by the High Energy Stereoscopic System. It has an unexpectedly asymmetric very-high-energy morphology that is offset from the cluster center, in addition to a large-scale, offset radio structure and compact diffuse X-ray emission associated with this cluster. We present new data from the Fermi Large Area Telescope on this source. We model the updated broadband spectral energy distribution, attributing this to cumulative pulsed emission from a population of embedded millisecond pulsars as well as unpulsed emission from the interaction of their leptonic winds with the ambient magnetic and soft-photon fields. In particular, our model invokes unpulsed synchrotron and inverse Compton components to model the radio and TeV data, cumulative pulsed curvature radiation to fit the Fermi data, and explains the hard Chandra X-ray spectrum via a "new" cumulative synchrotron component from electron-positron pairs within the pulsar magnetospheres that has not been implemented before. We find reasonable spectral fits for plausible model parameters. We also derive constraints on the millisecond pulsar luminosity function using the diffuse X-ray data and the Chandra sensitivity. Future higher-quality spectral and spatial data will help discriminate between competing scenarios (such as dark matter annihilation, white dwarf winds or hadronic interactions) proposed for the broadband emission as well as constrain degenerate model parameters., 17 pages, 1 figure, and 2 tables
Published: 2019
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28. A Fundamental Plane for Gamma-Ray Pulsars

Author: Zorawar Wadiasingh, Constantinos Kalapotharakos, Demosthenes Kazanas, and Alice K. Harding
Subjects: Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, Gamma ray, Synchrotron radiation, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Curvature, 01 natural sciences, Current sheet, Pulsar, Space and Planetary Science, Millisecond pulsar, 0103 physical sciences, Fundamental plane (elliptical galaxies), Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Fermi Gamma-ray Space Telescope
Abstract: We show that the $\gamma$-ray pulsar observables, i.e., their total $\gamma$-ray luminosity, $L_{\gamma}$, spectral cut-off energy, $\epsilon_{\rm cut}$, stellar surface magnetic field, $B_{\star}$, and spin-down power $\dot{\mathcal{E}}$, obey a relation of the form $L_{\gamma}=f(\epsilon_{\rm cut},B_{\star},\dot{\mathcal{E}})$, which represents a 3D plane in their 4D log-space. Fitting the data of 88 pulsars of the second Fermi pulsar catalog, we show this relation to be $L_{\gamma}\propto \epsilon_{\rm cut}^{1.18\pm 0.24}B_{\star}^{0.17\pm 0.05}\dot{\mathcal{E}}^{0.41\pm 0.08}$, a pulsar fundamental plane (FP). We show that the observed FP is remarkably close to the theoretical relation $L_{\gamma}\propto \epsilon_{\rm cut}^{4/3}B_{\star}^{1/6}\dot{\mathcal{E}}^{5/12}$ obtained assuming that the pulsar $\gamma$-ray emission is due to curvature radiation by particles accelerated at the pulsar equatorial current sheet just outside the light cylinder. Interestingly, the FP seems incompatible with emission by synchrotron radiation. The corresponding scatter about the FP is $\sim 0.35$dex and can only partly be explained by the observational errors while the rest is probably due to the variation of the inclination and observer angles. We predict also that $\epsilon_{\rm cut}\propto \dot{\mathcal{E}}^{7/16}$ toward low $\dot{\mathcal{E}}$ for both young and millisecond pulsars implying that the observed death-line of $\gamma$-ray pulsars is due to $\epsilon_{\rm cut}$ dropping below the Fermi-band. Our results provide a comprehensive interpretation of the observations of $\gamma$-ray pulsars, setting requirement for successful theoretical modeling., Comment: 8 pages, 6 figures, accepted for publication in ApJL
Published: 2019

29. Large High-precision X-Ray Timing of Three Millisecond Pulsars with $NICER$: Stability Estimates and Comparison with Radio

Author: Samuel R. Price, R. Spiewak, Paul Demorest, Sarah J. Vigeland, Slavko Bogdanov, W. W. Zhu, Timothy Dolch, Michael T. Lam, Julia S. Deneva, Peter A. Gentile, Cherry Ng, Zaven Arzoumanian, Harsha Blumer, D. R. Lorimer, N. Garver-Daniels, Maura McLaughlin, K. S. Wood, Matthew Kerr, J. Doty, Paul S. Ray, Scott M. Ransom, C. B. Markwardt, C. Malacaria, Joseph K. Swiggum, J. A. Ellis, Ingrid H. Stairs, M. L. Jones, Sebastien Guillot, Emmanuel Fonseca, Andrea N. Lommen, Paul R. Brook, Alice K. Harding, Kevin Stovall, Kevin Black, L. Guillemot, Robert D. Ferdman, David J. Nice, Timothy T. Pennucci, Luke M. Winternitz, Ismaël Cognard, M. T. Wolff, E. C. Ferrara, Ryan S. Lynch, H. T. Cromartie, M. E. DeCesar, Paul T. Baker, Natalia Lewandowska, Keith Gendreau, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, 01 natural sciences, 7. Clean energy, Stability (probability), stars: neutron, Pulsar, Millisecond pulsar, pulsars: general, 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Neutron Star Interior Composition Explorer, Sigma, Order (ring theory), Astronomy and Astrophysics, Interstellar medium, pulsars: individual, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Noise (radio)
Abstract: The Neutron Star Interior Composition Explorer (NICER) is an X-ray astrophysics payload on the International Space Station. It enables unprecedented high-precision timing of millisecond pulsars without the pulse broadening and delays due to dispersion and scattering within the interstellar medium that plague radio timing. We present initial timing results from a year of data on the millisecond pulsars PSR B1937+21 and PSR J0218+4232, and nine months of data on PSR B1821-24. NICER time-of-arrival uncertainties for the three pulsars are consistent with theoretical lower bounds and simulations based on their pulse shape templates and average source and background photon count rates. To estimate timing stability, we use the $\sigma_z$ measure, which is based on the average of the cubic coefficients of polynomial fits to subsets of timing residuals. So far we are achieving timing stabilities $\sigma_z \approx 3 \times 10^{-14}$ for PSR B1937+21 and on the order of $10^{-12}$ for PSRs B1821$-$24 and J0218+4232. Within the span of our \textit{NICER} data we do not yet see the characteristic break point in the slope of $\sigma_z$; detection of such a break would indicate that further improvement in the cumulative root-mean-square (RMS) timing residual is limited by timing noise. We see this break point in our comparison radio data sets for PSR B1821-24 and PSR B1937+21 on time scales of $> 2$ years., Comment: 30 pages, 15 figures; accepted to ApJ
Published: 2019
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30. Neutron Star Interior Composition Explorer X-Ray Timing of the Radio and $\gamma$-Ray Quiet Pulsars PSR J1412+7922 and PSR J1849-0001

Author: Alice K. Harding, Sridhar S. Manthripragada, Zaven Arzoumanian, Christian Malacaria, Slavko Bogdanov, Wynn C. G. Ho, Teruaki Enoto, Keith C. Gendreau, Sebastien Guillot, Gaurava K. Jaisawal, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, individual (PSR J1412+7922, PSR J1849-0001) [Pulsars], Astrophysics::High Energy Astrophysical Phenomena, general [Pulsars], FOS: Physical sciences, X-rays: stars, Astrophysics, Ephemeris, 01 natural sciences, Spectral line, Gravitational waves, stars: neutron, Pulsar, pulsars: general, 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, stars [X-rays], High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Neutron Star Interior Composition Explorer, Gravitational wave, Gamma ray, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, neutron [Stars], LIGO, Neutron star, pulsars: individual, gravitational waves, 13. Climate action, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: We present new timing and spectral analyses of PSR J1412+7922 (Calvera) and PSR J1849-0001, which are only seen as pulsars in X-rays, based on observations conducted with the Neutron Star Interior Composition Explorer (NICER). We obtain updated and substantially improved pulse ephemerides compared to previous X-ray studies, as well as spectra that can be well-fit by simple blackbodies and/or a power law. Our refined timing measurements enable deeper searches for pulsations at other wavelengths and sensitive targeted searches by LIGO/Virgo for continuous gravitational waves from these neutron stars. Using the sensitivity of LIGO's first observing run, we estimate constraints that a gravitational wave search of these pulsars would obtain on the size of their mass deformation and r-mode fluid oscillation., 12 pages, 4 figures; submitted to the Astrophysical Journal
Published: 2019
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31. Multi-Wavelength Polarimetry of Isolated Pulsars

Author: Alice K. Harding
Subjects: Physics, Neutron star, Wavelength, Pulsar, Crab Pulsar, Astrophysics::High Energy Astrophysical Phenomena, Polarimetry, Magnetosphere, Astrophysics, Radiation, Magnetic field
Abstract: Isolated pulsars are ideal sources for polarisation studies since the radiation from pulsars generally covers a wide range of wavelengths from radio to very-high-energy γ-rays and the pulsed emission is closely tied to the local magnetic field direction. Although radio polarisation data exist for many pulsars, polarisation measurements at higher energies exist for only six sources. All six of these have optical polarisation measurements while only the Crab pulsar has measured polarisation in the X-ray band. One member of a small group of pulsars only visible at optical and X-ray wavelengths, thought to be powered by thermal emission from the cooling neutron star surface, has detected optical polarisation. This chapter will review the current multi-wavelength polarisation observations and the theoretical modelling by which we can probe the pulsar magnetosphere structure and emission mechanisms.
Published: 2019
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32. Opacities for photon splitting and pair creation in neutron star magnetospheres

Author: Kun Hu, Matthew G. Baring, Alice K. Harding, Zorawar Wadiasingh, and 26594080 - Wadiasingh, Zorawar
Subjects: Photon, Opacity, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Magnetar, 01 natural sciences, 7. Clean energy, Spectral line, magnetars [Stars], Polarization, 0103 physical sciences, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, 010306 general physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, non-thermal [Radiation mechanisms], Compton scattering, Astronomy and Astrophysics, Light curve, Neutron star, Space and Planetary Science, Magnetic fields, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Over the last four decades, persistent and flaring emission of magnetars observed by various telescopes has provided us with a suite of light curves and spectra in soft and hard X-rays, with no emission yet detected above around 1 MeV. Attenuation of such high-energy photons by magnetic pair creation and photon splitting is expected to be active in the magnetospheres of magnetars, possibly accounting for the paucity of gamma-rays in their signals. This paper explores polarization-dependent opacities for these two QED processes in static vacuum dipole magnetospheres of highly-magnetized neutron stars, calculating attenuation lengths and determining escape energies, which are the maximum photon energies for transparency out to infinity. The numerical trajectory integral analysis in flat and curved spacetimes provides upper bounds of a few MeV or less to the visible energies for magnetars for locales proximate to the stellar surface. Photon splitting opacity alone puts constraints on the possible emission locales in their magnetospheres: regions within field loops of maximum altitudes 2-4 stellar radii are not commensurate with maximum detected energies of around 250 keV. These constraints apply not only to magnetar flares but also to their quiescent hard X-ray tail emission. An exploration of photon splitting attenuation in the context of a resonant inverse Compton scattering model for the hard X-ray tails derives distinctive phase-resolved spectroscopic and polarimetric signatures, of significant interest for future MeV-band missions such as AMEGO and e-ASTROGAM., 24 pages, 10 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society
Published: 2019

33. A NICER View of PSR J0030+0451: Millisecond Pulsar Parameter Estimation

Author: Zaven Arzoumanian, Sharon M. Morsink, Keith C. Gendreau, Alice K. Harding, Renee M. Ludlam, Tod E. Strohmayer, James M. Lattimer, Deepto Chakrabarty, Slavko Bogdanov, Anna V. Bilous, Sebastien Guillot, Wynn C. G. Ho, Paul S. Ray, Anna L. Watts, Thomas E. Riley, Charles Baker, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Nuclear Theory, 010504 meteorology & atmospheric sciences, Stellar mass, [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], FOS: Physical sciences, Astrophysics, 01 natural sciences, Nuclear Theory (nucl-th), Pulsar, Millisecond pulsar, 0103 physical sciences, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Neutron Star Interior Composition Explorer, Center (category theory), Spherical coordinate system, Astronomy and Astrophysics, Radius, Compact space, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: We report on Bayesian parameter estimation of the mass and equatorial radius of the millisecond pulsar PSR J0030$+$0451, conditional on pulse-profile modeling of Neutron Star Interior Composition Explorer (NICER) X-ray spectral-timing event data. We perform relativistic ray-tracing of thermal emission from hot regions of the pulsar's surface. We assume two distinct hot regions based on two clear pulsed components in the phase-folded pulse-profile data; we explore a number of forms (morphologies and topologies) for each hot region, inferring their parameters in addition to the stellar mass and radius. For the family of models considered, the evidence (prior predictive probability of the data) strongly favors a model that permits both hot regions to be located in the same rotational hemisphere. Models wherein both hot regions are assumed to be simply-connected circular single-temperature spots, in particular those where the spots are assumed to be reflection-symmetric with respect to the stellar origin, are strongly disfavored. For the inferred configuration, one hot region subtends an angular extent of only a few degrees (in spherical coordinates with origin at the stellar center) and we are insensitive to other structural details; the second hot region is far more azimuthally extended in the form of a narrow arc, thus requiring a larger number of parameters to describe. The inferred mass $M$ and equatorial radius $R_\mathrm{eq}$ are, respectively, $1.34_{-0.16}^{+0.15}$ M$_{\odot}$ and $12.71_{-1.19}^{+1.14}$ km, whilst the compactness $GM/R_\mathrm{eq}c^2 = 0.156_{-0.010}^{+0.008}$ is more tightly constrained; the credible interval bounds reported here are approximately the $16\%$ and $84\%$ quantiles in marginal posterior mass., Comment: Appears in ApJ Letters Focus Issue on NICER Constraints on the Dense Matter Equation of State; 76 pages, 24 figures, 7 tables, 8 figure sets (available in the online journal or from the authors)
Published: 2019
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34. PSR J0030+0451 Mass and Radius from $NICER$ Data and Implications for the Properties of Neutron Star Matter

Author: Alexander J. Dittmann, Yang Soong, Frederick K. Lamb, Paul S. Ray, Keith C. Gendreau, R. S. Foster, Teruaki Enoto, Sharon M. Morsink, Sebastien Guillot, Alice K. Harding, K. S. Wood, Takashi Okajima, James M. Lattimer, Simin Mahmoodifar, Renee M. Ludlam, Wynn C. G. Ho, M. C. Miller, Slavko Bogdanov, Gregory Y. Prigozhin, Zaven Arzoumanian, Tod E. Strohmayer, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, Nuclear Theory, [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 7. Clean energy, 01 natural sciences, Measure (mathematics), Gravitation, Nuclear Theory (nucl-th), Millisecond pulsar, 0103 physical sciences, Saturation (graph theory), 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Neutron Star Interior Composition Explorer, Equation of state (cosmology), Astronomy and Astrophysics, Radius, Neutron star, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Neutron stars are not only of astrophysical interest, but are also of great interest to nuclear physicists, because their attributes can be used to determine the properties of the dense matter in their cores. One of the most informative approaches for determining the equation of state of this dense matter is to measure both a star's equatorial circumferential radius $R_e$ and its gravitational mass $M$. Here we report estimates of the mass and radius of the isolated 205.53 Hz millisecond pulsar PSR J0030+0451 obtained using a Bayesian inference approach to analyze its energy-dependent thermal X-ray waveform, which was observed using the Neutron Star Interior Composition Explorer (NICER). This approach is thought to be less subject to systematic errors than other approaches for estimating neutron star radii. We explored a variety of emission patterns on the stellar surface. Our best-fit model has three oval, uniform-temperature emitting spots and provides an excellent description of the pulse waveform observed using NICER. The radius and mass estimates given by this model are $R_e = 13.02^{+1.24}_{-1.06}$ km and $M = 1.44^{+0.15}_{-0.14}\ M_\odot$ (68%). The independent analysis reported in the companion paper by Riley et al. (2019) explores different emitting spot models, but finds spot shapes and locations and estimates of $R_e$ and $M$ that are consistent with those found in this work. We show that our measurements of $R_e$ and $M$ for PSR J0030$+$0451 improve the astrophysical constraints on the equation of state of cold, catalyzed matter above nuclear saturation density., Comment: 49 pages, 16 figures, part of The Astrophysical Journal Letters focus issue on the Neutron Star Interior Composition Explorer
Published: 2019
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35. The Multipolar Magnetic Field of the Millisecond Pulsar PSR J0030+0451

Author: Constantinos Kalapotharakos, Zorawar Wadiasingh, Demosthenes Kazanas, and Alice K. Harding
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, X-ray astronomy, General relativity, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Markov chain Monte Carlo, Astrophysics, Gamma-ray astronomy, Magnetic field, symbols.namesake, Pulsar, Space and Planetary Science, Millisecond pulsar, symbols, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Modeling of the NICER X-ray waveform of the pulsar PSR J0030+0451, aimed to constrain the neutron star mass and radius, has inferred surface hot-spots (the magnetic polar caps) that imply significantly non-dipolar magnetic fields. To this end, we investigate magnetic field configurations that comprise offset dipole plus quadrupole components using static vacuum field and force-free global magnetosphere models. Taking into account the compactness and observer angle values provided by Miller et al. (2019) and Riley et al. (2019), we compute geodesics from the observer plane to the polar caps to compute the resulting X-ray light curve. We explore, through Markov chain Monte Carlo techniques, the detailed magnetic field configurations that can reproduce the observed X-ray light curve and have discovered degeneracies, i.e., diverse field configurations, which can provide sufficient descriptions to the NICER X-ray waveforms. Having obtained the force-free field structures, we then compute the corresponding synchronous gamma-ray light curves following Kalapotharakos et al. (2014) these we compare to those obtained by Fermi-LAT, to provide models consistent with both the X-ray and the gamma-ray data, thereby restricting further the multipole field parameters. An essential aspect of this approach is the proper computation of the relative phase between the synchronous X- and gamma-ray light curves. We conclude with a discussion of the broader implications of our study., 21 pages, 11 figures, accepted for publication in ApJ (minor update)
Published: 2021
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36. Learning about the magnetar Swift J1834.9−0846 from its wind nebula

Author: Matthew G. Baring, Chryssa Kouveliotou, George Younes, Alice K. Harding, R. Gill, Jonathan Granot, and Josef Gelfand
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Nebula, Astrophysics::High Energy Astrophysical Phenomena, Center (category theory), FOS: Physical sciences, Astronomy, Astronomy and Astrophysics, Astrophysics, Radius, Magnetar, 01 natural sciences, Emission nebula, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Magnetohydrodynamics, Astrophysics - High Energy Astrophysical Phenomena, 010306 general physics, Supernova remnant, Energy source, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: The first wind nebula around a magnetar was recently discovered in X-rays around Swift~J1834.9$-$0846. We study this magnetar's global energetics and the properties of its particle wind or outflows. At a distance of $\sim4\;$kpc, Swift~J1834.9$-$0846 is located at the center of the supernova remnant (SNR) W41 whose radius is $\sim 19\;$pc, an order of magnitude larger than that of the X-ray nebula ($\sim2\;$pc). The association with SNR W41 suggests a common age of $\sim5-100\;$kyr, while its spin-down age is $4.9$~kyr. A small natal kick velocity may partly explain why a wind nebula was detected around this magnetar but not around other magnetars, most of which appear to have larger kick velocities and may have exited their birth SNR. We find that the GeV and TeV source detected by Fermi/LAT and H.E.S.S., respectively, of radius $\sim11\;$pc is most likely of hadronic origin. The dynamics and internal structure of the nebula are examined analytically to explain the nebula's current properties. Its size may naturally correspond to the diffusion-dominated cooling length of the X-ray emitting $e^+e^-$ pairs. This may also account for the spectral softening of the X-ray emission from the nebula's inner to outer parts. Analysis of the X-ray synchrotron nebula implies that (i) the nebular magnetic field is $\gtrsim 11\;\mu$G (and likely $\lesssim30\;\mu$G), and (ii) the nebula is not powered predominantly by the magnetar's quiescent spin-down-powered MHD wind, but by other outflows that contribute most of its energy. The latter are most likely associated with the magnetar's bursting activity, and possibly dominated by outflows associated with its past giant flares. The energy source for the required outflows cannot be the decay of the magnetar's dipole field alone, and is most likely the decay of its much stronger internal magnetic field., Comment: 33 pages, 15 figures. Accepted for publication in MNRAS
Published: 2016
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37. Constraining the Emission Geometry and Mass of the White Dwarf Pulsar AR Sco Using the Rotating Vector Model

Author: Louis du Plessis, Alice K. Harding, Zorawar Wadiasingh, Christo Venter, 25936328 - Du Plessis, Louis, 12006653 - Venter, Christo, and 26594080 - Wadiasingh, Zorawar
Subjects: Non-thermal radiation sources, 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, Rotation powered pulsars, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, X-ray sources, 01 natural sciences, Orbital inclination, Pulsar, Binary pulsars, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Compact objects, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Optical pulsars, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Spin-½, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, White dwarf, Astronomy and Astrophysics, Optical polarization, Light curve, Position angle, Neutron star, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Magnetic fields, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, White dwarf stars
Abstract: We apply the standard radio pulsar rotating vector model to the white dwarf pulsar AR Sco's optical polarization position angle swings folded at the white dwarf's spin period as obtained by Buckley et al. (2017). Owing to the long duty cycle of spin pulsations with a good signal-to-noise ratio over the entire spin phase, in contrast to neutron star radio pulsars, we find well-constrained values for the magnetic obliquity $\alpha$ and observer viewing direction $\zeta$ with respect to the spin axis. We find $\cos\alpha=0.060^{+0.050}_{-0.053}$ and $\cos\zeta=0.49^{+0.09}_{-0.08}$, implying an orthogonal rotator with an observer angle $\zeta={60.4^\circ}^{+5.3^\circ}_{-6.0^\circ}$. This orthogonal nature of the rotator is consistent with the optical light curve consisting of two pulses per spin period, separated by $180^\circ$ in phase. Under the assumption that $\zeta \approx i$, where $i$ is the orbital inclination, and a Roche-lobe-filling companion M star, we obtain $m_{\rm WD} = 1.00^{+0.16}_{-0.10} M_\odot$ for the white dwarf mass. These polarization modeling results suggest the that non-thermal emission arises from a dipolar white dwarf magnetosphere and close to the star, with synchrotron radiation (if non-zero pitch angles can be maintained) being the plausible loss mechanism, marking AR Sco as an exceptional system for future theoretical and observational study., Comment: 11 pages, 7 figures, accepted by ApJ
Published: 2019
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38. NICER Discovers the Ultracompact Orbit of the Accreting Millisecond Pulsar IGR J17062-6143

Author: Keith C. Gendreau, Scott M. Ransom, Sebastien Guillot, Zaven Arzoumanian, Gaurava K. Jaisawal, Craig B. Markwardt, Matthew Kerr, Simin Mahmoodifar, Deepto Chakrabarty, Wynn C. G. Ho, Paul S. Ray, Tod E. Strohmayer, Michael T. Wolff, Jeroen Homan, Slavko Bogdanov, Laurens Keek, Ron Remillard, Teruaki Enoto, Peter Bult, Alice K. Harding, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Pulsar, Millisecond pulsar, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Circular orbit, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Solar mass, Neutron Star Interior Composition Explorer, 010308 nuclear & particles physics, Gravitational wave, Astronomy and Astrophysics, Orbital period, Neutron star, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present results of recent Neutron Star Interior Composition Explorer observations of the accreting millisecond X-ray pulsar IGR J17062-6143 that show that it resides in a circular, ultracompact binary with a 38 minute orbital period. NICER observed the source for approximately 26 ksec over a 5.3 day span in 2017 August, and again for 14 and 11 ksec in 2017 October and November, respectively. A power spectral analysis of the August exposure confirms the previous detection of pulsations at 163.656 Hz in Rossi X-ray Timing Explorer data, and reveals phase modulation due to orbital motion of the neutron star. A coherent search for the orbital solution using the Z^2 method finds a best-fitting circular orbit with a period of 2278.21 s (37.97 min), a projected semi-major axis of 0.00390 lt-sec, and a barycentric pulsar frequency of 163.6561105 Hz. This is currently the shortest known orbital period for an AMXP. The mass function is 9.12 e-8} solar masses, presently the smallest known for a stellar binary. The minimum donor mass ranges from about 0.005 - 0.007 solar masses, for a neutron star mass from 1.2 - 2 solar masses. Assuming mass transfer is driven by gravitational radiation, we find donor mass and binary inclination bounds of 0.0175 - 0.0155 solar masses and 19 deg < i < 27.5 deg, where the lower and upper bounds correspond to 1.4 and 2 solar mass neutron stars, respectively. Folding the data accounting for the orbital modulation reveals a sinusoidal profile with fractional amplitude 2.04 +- 0.11 % (0.3 - 3.2 keV)., 19 pages, 7 figures, published in the Astrophysical Journal Letters
Published: 2018
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39. Fermi-LAT Observations of LIGO/Virgo Event GW170817

Author: G. Chiaro, Marco Ajello, Diego F. Torres, Stefano Ciprini, J. B. Thayer, G. Jóhannesson, E. Moretti, Eleonora Troja, Nicola Omodei, Ronaldo Bellazzini, R. Buehler, E. J. Siskind, J. F. Ormes, Chong Yang, L. Guillemot, E. Orlando, T. J. Brandt, Stefan Funk, J. Li, Peter F. Michelson, Magnus Axelsson, L. R. Cominsky, Igor V. Moskalenko, Elliott D. Bloom, S. Cutini, A. A. Moiseev, Marcello Giroletti, Olaf Reimer, D. Horan, F. Loparco, Carmelo Sgrò, Riccardo Rando, A. Chekhtman, Johan Bregeon, P. Lubrano, Francesco Longo, I. A. Grenier, E. Cavazzuti, David H. Green, R. A. Cameron, J. L. Racusin, A. Reimer, Nicola Giglietto, E. Nuss, David Paneque, C. Favuzzi, Gloria Spandre, M. Kuss, Vahé Petrosian, Giacomo Principe, James Chiang, F. de Palma, F. Gargano, Johann Cohen-Tanugi, P. Fusco, L. Di Venere, Roger Blandford, Hiroyasu Tajima, Roopesh Ojha, Gabrijela Zaharijas, Denis Bastieri, Luca Latronico, K. S. Wood, J. G. Thayer, M. Di Mauro, Gino Tosti, D. Dumora, Elizabeth C. Ferrara, B. Berenji, Giacomo Vianello, M. N. Lovellette, P. A. Caraveo, J. M. Casandjian, R. Bonino, J. Granot, Steven Ritz, D. J. Suson, T. H. Burnett, C. C. Cheung, F. Piron, J. Valverde, Alice K. Harding, Melissa Pesce-Rollins, Tonia M. Venters, G. La Mura, Regina Caputo, N. Di Lalla, Luca Baldini, M. Takahashi, M. Palatiello, M. E. Monzani, M. N. Mazziotta, D. Tak, Sylvain Guiriec, R. Gill, Anna Franckowiak, D. Costantin, S. Rainò, Tsunefumi Mizuno, Vaidehi S. Paliya, Yasushi Fukazawa, P. M. Saz Parkinson, J. D. Magill, Soebur Razzaque, Alice Allafort, Elisabetta Bissaldi, P. Bruel, Matthew G. Baring, Sara Buson, T. A. Porter, Daniel Kocevski, Fumiya Imazato, T. Glanzman, R. Dubois, E. Hays, P. Spinelli, Francesco Giordano, F. Spada, Eugenio Bottacini, Alberto Manfreda, Dario Gasparrini, Stefan Larsson, M. Razzano, Filippo D'Ammando, Alessandro Cuoco, M.-H. Grondin, S. Maldera, T. Kamae, Eleonora Torresi, Massimo Persic, Felix Ryde, Guido Barbiellini, L. S. Rochester, S. Kensei, Matteo Negro, A. Morselli, ITA, Laboratoire Univers et Particules de Montpellier (LUPM), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Leprince-Ringuet (LLR), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Ajello, M., Allafort, A., Axelsson, M., Baldini, L., Barbiellini, G., Baring, M. G., Bastieri, D., Bellazzini, R., Berenji, B., Bissaldi, E., Blandford, R. D., Bloom, E. D., Bonino, R., Bottacini, E., Brandt, T. J., Bregeon, J., Bruel, P., Buehler, R., Burnett, T. H., Buson, S., Cameron, R. A., Caputo, R., Caraveo, P. A., Casandjian, J. M., Cavazzuti, E., Chekhtman, A., Cheung, C. C., Chiang, J., Chiaro, G., Ciprini, S., Cohen-Tanugi, J., Cominsky, L. R., Costantin, D., Cuoco, A., Cutini, S., D'Ammando, F., Palma, F. De, Lalla, N. Di, Mauro, M. Di, Venere, L. Di, Dubois, R., Dumora, D., Favuzzi, C., Ferrara, E. C., Franckowiak, A., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Gill, R., Giordano, F., Giroletti, M., Glanzman, T., Granot, J., Green, D., Grenier, I. A., Grondin, M. -H., Guillemot, L., Guiriec, S., Harding, A. K., Hays, E., Horan, D., Imazato, F., Jóhannesson, G., Kamae, T., Kensei, S., Kocevski, D., Kuss, M., Mura, G. La, Larsson, S., Latronico, L., Li, J., Longo, F., Loparco, F., Lovellette, M. N., Lubrano, P., Magill, J. D., Maldera, S., Manfreda, A., Mazziotta, M. N., Michelson, P. F., Mizuno, T., Moiseev, A. A., Monzani, M. E., Moretti, E., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Ojha, R., Omodei, N., Orlando, E., Ormes, J. F., Palatiello, M., Paliya, V. S., Paneque, D., Persic, M., Pesce-Rollins, M., Petrosian, V., Piron, F., Porter, T. A., Principe, G., Racusin, J. L., Raino, S., Rando, R., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Ritz, S., Rochester, L. S., Ryde, F., Parkinson, P. M. Saz, Sgro, C., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Suson, D. J., Tajima, H., Takahashi, M., Tak, D., Thayer, J. G., Thayer, J. B., Torres, D. F., Torresi, E., Tosti, G., Troja, E., Valverde, J., Venters, T. M., Vianello, G., Wood, K., Yang, C., Zaharijas, G., Raunvísindastofnun (HÍ), Science Institute (UI), Verkfræði- og náttúruvísindasvið (HÍ), School of Engineering and Natural Sciences (UI), Háskóli Íslands, University of Iceland, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES)
Subjects: neutron star: binary, Gammageislar, gamma-ray burst: general, Astrophysics, general [gamma-ray burst], 01 natural sciences, Gamma-ray, Luminosity, gamma rays: general, gravitational waves, gamma ray: flux, LIGO, gravitational wave, 010303 astronomy & astrophysics, Physics, energy: high, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Gamma-ray burst: general, Astrophysics::High Energy Astrophysical Phenomena, Context (language use), Astrophysics::Cosmology and Extragalactic Astrophysics, gamma ray: burst, gravitational radiation: direct detection, GLAST, Gravitational waves, binary: coalescence, 0103 physical sciences, ddc:530, 010306 general physics, Gamma-ray burst, Astrophysics::Galaxy Astrophysics, Gravitational wave, Astronomy and Astrophysics, trigger, Astronomy and Astrophysic, Stjarneðlisfræði, redshift, Redshift, gravitational radiation detector, Neutron star, electromagnetic, VIRGO, [SDU]Sciences of the Universe [physics], Space and Planetary Science, gravitational radiation: emission, ddc:520, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], general [gamma rays], Fermi Gamma-ray Space Telescope
Abstract: Publisher's version (útgefin grein), We present the Fermi Large Area Telescope (LAT) observations of the binary neutron star merger event GW170817 and the associated short gamma-ray burst (SGRB) GRB 170817A detected by the Fermi Gamma-ray Burst Monitor. The LAT was entering the South Atlantic Anomaly at the time of the LIGO/Virgo trigger (t GW) and therefore cannot place constraints on the existence of high-energy (E > 100 MeV) emission associated with the moment of binary coalescence. We focus instead on constraining high-energy emission on longer timescales. No candidate electromagnetic counterpart was detected by the LAT on timescales of minutes, hours, or days after the LIGO/Virgo detection. The resulting flux upper bound (at 95% C.L.) from the LAT is 4.5 × 10−10 erg cm−2 s−1 in the 0.1–1 GeV range covering a period from t GW + 1153 s to t GW + 2027 s. At the distance of GRB 170817A, this flux upper bound corresponds to a luminosity upper bound of 9.7 × 1043 erg s−1, which is five orders of magnitude less luminous than the only other LAT SGRB with known redshift, GRB 090510. We also discuss the prospects for LAT detection of electromagnetic counterparts to future gravitational-wave events from Advanced LIGO/Virgo in the context of GW170817/GRB 170817A., This work performed in part under DOE Contract DE-AC02-76SF00515.
Published: 2018
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40. Multi-TeV emission from the Vela pulsar

Author: Alice K. Harding, Christo Venter, Constantinos Kalapotharakos, Monica Barnard, 20574266 - Barnard, Monica, and 12006653 - Venter, Christo
Subjects: Photon, Astrophysics::High Energy Astrophysical Phenomena, Magnetosphere, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Vela, 01 natural sciences, Article, law.invention, Current sheet, Pulsar, law, individual (Vela pulsar) [Pulsars], 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, stars [Gamma rays], Astronomy and Astrophysics, Synchrotron, Particle acceleration, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract: Pulsed emission from the Vela pulsar at energies above 3 TeV has recently been detected by the H.E.S.S. II air-Cherenkov telescope. We present a model for the broad-band spectrum of Vela from infra-red (IR) to beyond 10 TeV. Recent simulations of the global pulsar magnetosphere have shown that most of the particle acceleration occurs in the equatorial current sheet outside the light cylinder and that the magnetic field structure is nearly force-free for younger pulsars. We adopt this picture to compute the radiation from both electron-positron pairs produced in polar cap cascades and from primary particles accelerated in the separatrix and current sheet. The synchrotron spectrum from pairs resonantly absorbing radio photons at relatively low altitude can account for the observed IR-optical emission. We set the parallel electric field in the current sheet to produce the Fermi GeV emission through curvature radiation, producing particles with energies of 30-60 TeV. These particles then produce Very-High-Energy emission up to around 30 TeV through inverse-Compton scattering of the IR-Optical emission. We present model spectra and light curves that can match the IR-Optical, GeV and make predictions for the multi-TeV emission., Comment: 11 pages, 3 figures, accepted for publication in Astrophysical Journal Letters
Published: 2018

41. Gamma-ray pulsars: A gold mine

Author: Isabelle Grenier, Alice K. Harding, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), and Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112))
Subjects: Pulsa, accelerator, Astrophysics::High Energy Astrophysical Phenomena, Acceleration, FOS: Physical sciences, Neutron star, Energy Engineering and Power Technology, magnetic field, Astrophysics, rotation, 7. Clean energy, GLAST, law.invention, particle: acceleration, Gravitation, star, Pulsar, law, Magnétosphère, Rayons gamma, Accélération, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, nucleus, Gamma rays, General Engineering, Gamma ray, Astronomy, Particle accelerator, Étoile à neutrons, gold, radiation: pulsed, Particle acceleration, Stars, gravitation, gamma ray, Magnetosphere, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Fermi Gamma-ray Space Telescope
Abstract: The most energetic neutron stars, powered by their rotation, are capable of producing pulsed radiation from the radio up to gamma rays with nearly TeV energies. These pulsars are part of the universe of energetic and powerful particle accelerators, using their uniquely fast rotation and formidable magnetic fields to accelerate particles to ultra-relativistic speed. The extreme properties of these stars provide an excellent testing ground, beyond Earth experience, for nuclear, gravitational, and quantum-electrodynamical physics. A wealth of gamma-ray pulsars has recently been discovered with the Fermi Gamma-Ray Space Telescope. The energetic gamma rays enable us to probe the magnetospheres of neutron stars and particle acceleration in this exotic environment. We review the latest developments in this field, beginning with a brief overview of the properties and mysteries of rotation-powered pulsars, and then discussing gamma-ray observations and magnetospheric models in more detail., Comment: 24-page review for the book 'High-energy gamma-ray astronomy', eds. B. Degrange, G. Fontaine, volume 1, Comptes Rendus Physique, Elsevier, C. R. Physique 16, 2015
Published: 2015
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42. X-Ray and Radio Observations of the Magnetar SGR J1935+2154 during Its 2014, 2015, and 2016 Outbursts

Author: Ramandeep Gill, Alice K. Harding, Ersin Gogus, Lin Lin, Amruta Jaodand, Jonathan Granot, George Younes, Matthew G. Baring, Jason W. T. Hessels, Neil Gehrels, Daniela Huppenkothen, Alexander J. van der Horst, Chryssa Kouveliotou, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Astrophysics::High Energy Astrophysical Phenomena, Theoretical models, X-ray, FOS: Physical sciences, Flux, Astronomy and Astrophysics, Astrophysics, Magnetar, 01 natural sciences, Imaging analysis, 13. Climate action, Space and Planetary Science, 0103 physical sciences, Density limit, Maximum flux, Astrophysics - High Energy Astrophysical Phenomena, 010306 general physics, 010303 astronomy & astrophysics
Abstract: We analyzed broad-band X-ray and radio data of the magnetar SGR J1935+2154 taken in the aftermath of its 2014, 2015, and 2016 outbursts. The source soft X-ray spectrum, Comment: 17 pages, 7 figures, 5 tables, submitted to ApJ, comments welcome
Published: 2017

43. The Fermi Galactic Center GeV Excess and Implications for Dark Matter

Author: Dario Gasparrini, J. Ballet, Francesco Longo, Elisabetta Bissaldi, L. Latronico, Miguel A. Sánchez-Conde, K. Tanaka, P. Bruel, A. S. Johnson, S. W. Digel, T. Ohsugi, M. Orienti, M. Ackermann, Eric Charles, Eleonora Troja, D. Malyshev, Yasunobu Uchiyama, T. H. Burnett, Soebur Razzaque, S. Maldera, F. Costanza, T. Kamae, Warit Mitthumsiri, M. Razzano, Filippo D'Ammando, John W. Hewitt, T. Jogler, G. Barbiellini, M. Kuss, M. Di Mauro, F. de Palma, D. J. Suson, W. B. Focke, T. J. Brandt, Gabrijela Zaharijas, Frederic Piron, Alice K. Harding, Diego F. Torres, Giacomo Principe, Alessandro Cuoco, W. B. Atwood, J. S. Perkins, Matthew Wood, E. Orlando, L. Tibaldo, Jingcheng Li, James Chiang, Andrea Chiappo, Francesco Giordano, Nicola Giglietto, R. Desiante, Roger Blandford, M. Caragiulo, R. A. Cameron, P. Spinelli, R. Buehler, Elizabeth C. Ferrara, Giacomo Vianello, Matteo Negro, A. Morselli, M. N. Lovellette, J. Bregeon, P. A. Caraveo, R. Bonino, Nestor Mirabal, Massimo Persic, Persis S. Drell, Ronaldo Bellazzini, Peter F. Michelson, Marcello Giroletti, K. S. Wood, Olaf Reimer, D. Horan, A. Chekhtman, P. Lubrano, S. Rainò, N. Di Lalla, Luca Baldini, Elliott D. Bloom, Claudia Cecchi, Sylvain Guiriec, Andrea Albert, F. Spada, R. Caputo, F. Gargano, Hiroyasu Tajima, S. J. Fegan, Jan Conrad, Stefan Larsson, C. Favuzzi, G. La Mura, E. J. Siskind, M. N. Mazziotta, M. Gustafsson, Melissa Pesce-Rollins, Pierrick Martin, J. D. Magill, G. A. Gomez-Vargas, Anna Franckowiak, Tsunefumi Mizuno, A. Reimer, E. Hays, Stephan Zimmer, G. Chiaro, J. E. Grove, Yasushi Fukazawa, S. Cutini, A. A. Moiseev, D. Kocevski, T. Glanzman, F. Loparco, M. E. Monzani, Eugenio Bottacini, Alberto Manfreda, Denis Bastieri, S. Ciprini, Marco Ajello, J. B. Thayer, J. F. Ormes, P. Fusco, Stefan Funk, Carmelo Sgrò, Riccardo Rando, D. Simone, David Paneque, I. A. Grenier, E. Cavazzuti, David H. Green, Gloria Spandre, L. Guillemot, E. Nuss, L. Di Venere, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Particules de Montpellier (LUPM), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Leprince-Ringuet (LLR), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Fermi-LAT, Ackermann, M., Ajello, M., Albert, A., Atwood, W. B., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Blandford, R. D., Bloom, E. D., Bonino, R., Bottacini, E., Brandt, T. J., Bregeon, J., Bruel, P., Buehler, R., Burnett, T. H., Cameron, R. A., Caputo, R., Caragiulo, M., Caraveo, P. A., Cavazzuti, E., Cecchi, C., Charles, E., Chekhtman, A., Chiang, J., Chiappo, A., Chiaro, G., Ciprini, S., Conrad, J., Costanza, F., Cuoco, A., Cutini, S., D'Ammando, F., De Palma, F., Desiante, R., Digel, S. W., Di Lalla, N., Di Mauro, M., Di Venere, L., Drell, P. S., Favuzzi, C., Fegan, S. J., Ferrara, E. C., Focke, W. B., Franckowiak, A., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giordano, F., Giroletti, M., Glanzman, T., Gomez-Vargas, G. A., Green, D., Grenier, I. A., Grove, J. E., Guillemot, L., Guiriec, S., Gustafsson, M., Harding, A. K., Hays, E., Hewitt, J. W., Horan, D., Jogler, T., Johnson, A. S., Kamae, T., Kocevski, D., Kuss, M., La Mura, G., Larsson, S., Latronico, L., Li, J., Longo, F., Loparco, F., Lovellette, M. N., Lubrano, P., Magill, J. D., Maldera, S., Malyshev, D., Manfreda, A., Martin, P., Mazziotta, M. N., Michelson, P. F., Mirabal, N., Mitthumsiri, W., Mizuno, T., Moiseev, A. A., Monzani, M. E., Morselli, A., Negro, M., Nuss, E., Ohsugi, T., Orienti, M., Orlando, E., Ormes, J. F., Paneque, D., Perkins, J. S., Persic, M., Pesce-Rollins, M., Piron, F., Principe, G., Raino, S., Rando, R., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Sanchez-Conde, M., Sgro, C., Simone, D., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Suson, D. J., Tajima, H., Tanaka, K., Thayer, J. B., Tibaldo, L., Torres, D. F., Troja, E., Uchiyama, Y., Vianello, G., Wood, K. S., Wood, M., Zaharijas, G., Zimmer, S., Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Laboratoire AIM, Université Paris Diderot - Paris 7 ( UPD7 ) -Centre d'Etudes de Saclay, Laboratoire Univers et Particules de Montpellier ( LUPM ), Centre National de la Recherche Scientifique ( CNRS ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Université Montpellier 2 - Sciences et Techniques ( UM2 ) -Université de Montpellier ( UM ), Laboratoire Leprince-Ringuet ( LLR ), Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -École polytechnique ( X ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace ( LPC2E ), Centre National de la Recherche Scientifique ( CNRS ) -Université d'Orléans ( UO ) -Institut national des sciences de l'Univers ( INSU - CNRS ), Unité Scientifique de la Station de Nançay ( USN ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS ), Institut de recherche en astrophysique et planétologie ( IRAP ), Université Paul Sabatier - Toulouse 3 ( UPS ) -Observatoire Midi-Pyrénées ( OMP ) -Centre National de la Recherche Scientifique ( CNRS ), D’Ammando, F., Palma, F. de, Lalla, N. Di, Mauro, M. Di, Venere, L. Di, Gomez Vargas, G. A., Mura, G. La, Longo, Francesco, Pesce Rollins, M., Rainò, S., Sánchez Conde, M., Sgrò, C., Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and ITA
Subjects: [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Astrophysics, 01 natural sciences, Galaxy: bulge, propagation, gamma ray: flux, 010303 astronomy & astrophysics, cosmic ray, Physics, general [ISM], Galaxy: center, Galactic Center, center [Galaxy], gamma ray: emission, cosmic radiation, Astrophysics - High Energy Astrophysical Phenomena, Milky Way, Astrophysics::High Energy Astrophysical Phenomena, Dark matter, bulge [Galaxy], Cosmic ray, Astrophysics::Cosmology and Extragalactic Astrophysics, cosmic rays, Galaxy: halo, gamma rays: general, ISM: general, Astronomy and Astrophysics, Space and Planetary Science, cross section: annihilation, Galactic halo, gas, 0103 physical sciences, conservation law, halo [Galaxy], Astrophysics::Galaxy Astrophysics, 010308 nuclear & particles physics, background, bubble, Astronomy, dark matter: annihilation, Galactic plane, Galaxy, [SDU]Sciences of the Universe [physics], ddc:520, galaxy, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], general [gamma rays], Fermi Gamma-ray Space Telescope
Abstract: The region around the Galactic center (GC) is now well established to be brighter at energies of a few GeV than expected from conventional models of diffuse gamma-ray emission and catalogs of known gamma-ray sources. We study the GeV excess using 6.5 years of data from the Fermi Large Area Telescope. We characterize the uncertainty of the GC excess spectrum and morphology due to uncertainties in cosmic-ray source distributions and propagation, uncertainties in the distribution of interstellar gas in the Milky Way, and uncertainties due to a potential contribution from the Fermi bubbles. We also evaluate uncertainties in the excess properties due to resolved point sources of gamma rays. The Galactic center is of particular interest as it would be expected to have the brightest signal from annihilation of weakly interacting massive dark matter particles. However, control regions along the Galactic plane, where a dark-matter signal is not expected, show excesses of similar amplitude relative to the local background. Based on the magnitude of the systematic uncertainties, we conservatively report upper limits for the annihilation cross section as function of particle mass and annihilation channel., Comment: Contact authors: A. Albert, E. Charles, A. Franckowiak, D. Malyshev, L. Tibaldo. 63 pages, 34 figures. Published in ApJ
Published: 2017
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44. 3FHL: The Third Catalog of Hard Fermi-LAT Sources

Author: Igor V. Moskalenko, Lukasz Stawarz, Olaf Reimer, Seb. Funk, Diego F. Torres, Nicola Omodei, M. Razzano, M.-H. Grondin, Filippo D'Ammando, C. Favuzzi, M. Caragiulo, Alessandro Cuoco, E. J. Siskind, Jean Ballet, R. A. Cameron, F. Piron, Stefano Ciprini, J. M. Cohen, Alice K. Harding, M. N. Mazziotta, Seth Digel, Francesco Longo, R. Desiante, S. Cutini, A. A. Moiseev, Elliott D. Bloom, Jingcheng Li, Pascal Bruel, R. Buehler, F. Spada, D. Horan, Aaron Dominguez, Stefan Larsson, Marco Ajello, J. B. Thayer, F. Loparco, Peter F. Michelson, Marcello Giroletti, C. C. Cheung, N. Di Lalla, M. Di Mauro, Luca Baldini, M. Takahashi, T. Reposeur, Benoit Lott, Roger Blandford, P. Fusco, Sara Buson, D. J. Thompson, M. Palatiello, R. J. Britto, John W. Hewitt, F. de Palma, Sylvain Guiriec, R. Bonino, S. J. Fegan, A. Reimer, T. A. Porter, Matthew Wood, Johan Bregeon, Giacomo Principe, E. Orlando, Julie McEnery, Kent S. Wood, F. Gargano, Nestor Mirabal, P. Fortin, Soebur Razzaque, Luca Latronico, Giacomo Vianello, G. La Mura, Elizabeth C. Ferrara, J. G. Thayer, Regina Caputo, D. Costantin, D. Dumora, A. Chekhtman, P. Lubrano, W. B. Atwood, Ronaldo Bellazzini, Vaidehi S. Paliya, M. E. Monzani, J. S. Perkins, Nicola Giglietto, E. Hays, Anna Franckowiak, S. Rainò, Tsunefumi Mizuno, G. Chiaro, P. A. Caraveo, J. E. Grove, Yasushi Fukazawa, Persis S. Drell, J. D. Magill, Eric Charles, Manuel Meyer, D. J. Suson, Melissa Pesce-Rollins, I. A. Grenier, Dario Gasparrini, Warit Mitthumsiri, E. Cavazzuti, David H. Green, Gloria Spandre, P. Spinelli, L. Di Venere, M. Lemoine-Goumard, Francesco Giordano, D. Tak, Carmelo Sgrò, Riccardo Rando, D. Simone, E. Nuss, David Paneque, M. Kuss, T. Ohsugi, Eleonora Troja, M. Orienti, S. Maldera, F. Costanza, Eleonora Torresi, Elisabetta Bissaldi, Gudlaugur Johannesson, Lucas Guillemot, Guido Barbiellini, Paolo Giommi, Massimo Persic, T. Glanzman, Alberto Manfreda, Denis Bastieri, Claudia Cecchi, S. Kensei, Matteo Negro, A. Morselli, P. M. Saz Parkinson, Department of Physics and Astronomy [Clemson], Clemson University, Santa Cruz Institute for Particle Physics (SCIPP), University of California [Santa Cruz] (UCSC), University of California-University of California, University of Pisa - Università di Pisa, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Istituto Nazionale di Fisica Nucleare, Sezione di Trieste (INFN, Sezione di Trieste), Istituto Nazionale di Fisica Nucleare (INFN), Istituto Nazionale di Fisica Nucleare, Sezione di Padova (INFN, Sezione di Padova), Istituto Nazionale di Fisica Nucleare [Pisa] (INFN), Stanford University, Istituto Nazionale di Fisica Nucleare, Sezione di Torino (INFN, Sezione di Torino), Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Laboratoire Leprince-Ringuet (LLR), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Max-Planck-Institut für Physik (Werner-Heisenberg-Institut) (MPI-P), Istituto Nazionale di Fisica Nucleare, sezione di Bari (INFN, sezione di Bari), Agenzia Spaziale Italiana (ASI) Science Data Center, George Mason University [Fairfax], Universita degli Studi di Padova, Laboratoire de l'Accélérateur Linéaire (LAL), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Istituto Nazionale di Fisica Nucleare, Sezione di Torino, Istituto Nazionale di Astrofisica (INAF), Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Humboldt-Universität zu Berlin, Erlangen Centre for Astroparticle Physics (ECAP), Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Science Institute, University of Iceland, University of Iceland [Reykjavik], Hiroshima City University, Istituto Nazionale di Fisica Nucleare, Sezione di Perugia (INFN, Sezione di Perugia), Laboratoire d'interaction du rayonnement X avec la matière (LIXAM), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), NASA Goddard Space Flight Center (GSFC), Mahidol University [Bangkok], Hiroshima University, Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tor Vergata (INFN, Sezione di Roma Tor Vergata), Istituto di Radioastronomia INAF, INAF - Osservatorio Astronomico di Trieste (OAT), PPM Group [University of Johannesburg], Department of Geology [University of Johannesburg], University of Johannesburg (UJ)-University of Johannesburg (UJ), NYCB Real-Time Computing Inc., Lattingtown, NYCB Real-Time Computing Inc. [Lattingtown], IEEC-CSIC, Universitat Autònoma de Barcelona (UAB), Istituto di Astrofisica Spaziale e Fisica cosmica - Bologna (IASF-Bo), Fermi-LAT Collaboration, Ajello, M., Atwood, W. B., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Blandford, R. D., Bloom, E. D., Bonino, R., Bregeon, J., Britto, R. J., Bruel, P., Buehler, R., Buson, S., Cameron, R. A., Caputo, R., Caragiulo, M., Caraveo, P. A., Cavazzuti, E., Cecchi, C., Charles, E., Chekhtman, A., Cheung, C. C., Chiaro, G., Ciprini, S., Cohen, J. M., Costantin, D., Costanza, F., Cuoco, A., Cutini, S., D'Ammando, F., De Palma, F., Desiante, R., Digel, S. W., Di Lalla, N., Di Mauro, M., Di Venere, L., Domnguez, A., Drell, P. S., Dumora, D., Favuzzi, C., Fegan, S. J., Ferrara, E. C., Fortin, P., Franckowiak, A., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giommi, P., Giordano, F., Giroletti, M., Glanzman, T., Green, D., Grenier, I. A., Grondin, M. -H., Grove, J. E., Guillemot, L., Guiriec, S., Harding, A. K., Hays, E., Hewitt, J. W., Horan, D., Jóhannesson, G., Kensei, S., Kuss, M., La Mura, G., Larsson, S., Latronico, L., Lemoine-Goumard, M., Li, J., Longo, F., Loparco, F., Lott, B., Lubrano, P., Magill, J. D., Maldera, S., Manfreda, A., Mazziotta, M. N., Mcenery, J. E., Meyer, M., Michelson, P. F., Mirabal, N., Mitthumsiri, W., Mizuno, T., Moiseev, A. A., Monzani, M. E., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Ohsugi, T., Omodei, N., Orienti, M., Orlando, E., Palatiello, M., Paliya, V. S., Paneque, D., Perkins, J. S., Persic, M., Pesce-Rollins, M., Piron, F., Porter, T. A., Principe, G., Raino, S., Rando, R., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Reposeur, T., Saz Parkinson, P. M., Sgro, C., Simone, D., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Stawarz, L., Suson, D. J., Takahashi, M., Tak, D., Thayer, J. G., Thayer, J. B., Thompson, D. J., Torres, D. F., Torresi, E., Troja, E., Vianello, G., Wood, K., Wood, M., National Institute for Nuclear Physics (INFN), Stanford University [Stanford], Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Humboldt Universität zu Berlin, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Universitat Autònoma de Barcelona [Barcelona] (UAB), ITA, University of California [Santa Cruz] (UC Santa Cruz), University of California (UC)-University of California (UC), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Università degli Studi di Padova = University of Padua (Unipd), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Humboldt University Of Berlin, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), and University of Johannesburg [South Africa] (UJ)-University of Johannesburg [South Africa] (UJ)
Subjects: catalog, Astrophysics::High Energy Astrophysical Phenomena, catalogs, gamma rays: general, FOS: Physical sciences, Energy flux, Flux, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 7. Clean energy, 01 natural sciences, Astronomy and Astrophysics, Space and Planetary Science, law.invention, Telescope, law, 0103 physical sciences, catalogs – gamma rays: general, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Astronomy, Galactic plane, Astronomy and Astrophysic, Redshift, Galaxy, Crab Nebula, [SDU]Sciences of the Universe [physics], ddc:520, Astrophysics - High Energy Astrophysical Phenomena, general [gamma rays], Fermi Gamma-ray Space Telescope
Abstract: We present a catalog of sources detected above 10 GeV by the Fermi Large Area Telescope (LAT) in the first 7 years of data using the Pass 8 event-level analysis. This is the Third Catalog of Hard Fermi-LAT Sources (3FHL), containing 1556 objects characterized in the 10 GeV - 2 TeV energy range. The sensitivity and angular resolution are improved by factors of 3 and 2 relative to the previous LAT catalog at the same energies (1FHL). The vast majority of detected sources (79%) are associated with extragalactic counterparts at other wavelengths, including 16 sources located at very high redshift ($z>2$). Eight percent of the sources have Galactic counterparts and 13% are unassociated (or associated with a source of unknown nature). The high-latitude sky and the Galactic plane are observed with a flux sensitivity of 4.4 to 9.5$\times 10^{-11}$ ph cm$^{-2}$ s$^{-1}$, respectively (this is approximately 0.5% and 1% of the Crab Nebula flux above 10 GeV). The catalog includes 214 new $\gamma$-ray sources. The substantial increase in the number of photons (more than 4 times relative to 1FHL and 10 times to 2FHL) also allows us to measure significant spectral curvature for 32 sources and find flux variability for 163 of them. Furthermore, we estimate that for the same flux limit of $10^{-12}$ erg cm$^{-2}$ s$^{-1}$, the energy range above 10 GeV has twice as many sources as above 50 GeV, highlighting the importance, for future Cherenkov telescopes, of lowering the energy threshold as much as possible., Comment: Accepted by ApJS. Contact authors: Alberto Dominguez, Marco Ajello, Benoit Lott, Sara Cutini, Pascal Fortin. The full FITS catalog will be made available at the FSSC: https://fermi.gsfc.nasa.gov/ssc/
Published: 2017
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45. Constraining Relativistic Bow Shock Properties in Rotation-Powered Millisecond Pulsar Binaries

Author: Christo Venter, Matthew G. Baring, Zorawar Wadiasingh, Alice K. Harding, and Markus Böttcher
Subjects: Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Electron, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Occultation, Article, Orbital inclination, Pulsar, Millisecond pulsar, 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Astronomy and Astrophysics, Light curve, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Phenomenology (particle physics), Fermi Gamma-ray Space Telescope
Abstract: Multiwavelength followup of unidentified Fermi sources has vastly expanded the number of known galactic-field "black widow" and "redback" millisecond pulsar binaries. Focusing on their rotation-powered state, we interpret the radio to X-ray phenomenology in a consistent framework. We advocate the existence of two distinct modes differing in their intrabinary shock orientation, distinguished by the phase-centering of the double-peaked X-ray orbital modulation originating from mildly-relativistic Doppler boosting. By constructing a geometric model for radio eclipses, we constrain the shock geometry as functions of binary inclination and shock stand-off $R_0$. We develop synthetic X-ray synchrotron orbital light curves and explore the model parameter space allowed by radio eclipse constraints applied on archetypal systems B1957+20 and J1023+0038. For B1957+20, from radio eclipses the stand-off is $R_0 \sim 0.15$ -- $0.3$ fraction of binary separation from the companion center, depending on the orbit inclination. Constructed X-ray light curves for B1957+20 using these values are qualitatively consistent with those observed, and we find occultation of the shock by the companion as a minor influence, demanding significant Doppler factors to yield double peaks. For J1023+0038, radio eclipses imply $R_0 \lesssim 0.4$ while X-ray light curves suggest $0.1\lesssim R_0 \lesssim 0.3$ (from the pulsar). Degeneracies in the model parameter space encourage further development to include transport considerations. Generically, the spatial variation along the shock of the underlying electron power-law index should yield energy-dependence in the shape of light curves motivating future X-ray phase-resolved spectroscopic studies to probe the unknown physics of pulsar winds and relativistic shock acceleration therein., Comment: Accepted to ApJ, 36 pages, 15 figures; comments welcome
Published: 2017
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46. Modelling energy-dependent pulsar light curves due to curvature radiation

Author: Monica Barnard, Alice K. Harding, Constantinos Kalapotharakos, Christo Venter, 20574266 - Barnard, Monica, and 12006653 - Venter, Christo
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Electromagnetic spectrum, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics, Light curve, Curvature, Vela, law.invention, Telescope, Pulsar, law, Astrophysics - High Energy Astrophysical Phenomena, Cherenkov radiation, Fermi Gamma-ray Space Telescope
Abstract: Pulsars emit pulsed emission across the entire electromagnetic spectrum and their light curve phenomenology is strongly dependent on energy. This is also true for the gamma-ray waveband. Continued detections by Fermi Large Area Telescope in the GeV band and ground-based Cherenkov telescopes in the TeV band (e.g., Crab and Vela above 1 TeV) raise important questions about our understanding of the electrodynamics and local environment of pulsar magnetospheres. We model energy-dependent light curves (as a function of geometry, e.g., pulsar inclination and observer angle) in the curvature radiation domain using a full emission code. We will discuss our refined calculation of the curvature radius of the particle trajectory and the effect thereof on the expected light curve shapes, as well as the origin of the light curve peaks in the magnetosphere. Our modelling should aid in differentiating between different emission mechanisms, as well as constraining the emission geometry by comparing our predictions to multi-wavelength data., 8 pages, 6 figures, Proceedings of the 5th Annual Conference on High Energy Astrophysics in Southern Africa (HEASA2017), accepted for publication in the online journal Proceedings of Science (ISSN 1824-8039) at https://pos.sissa.it. arXiv admin note: text overlap with arXiv:1710.08677
Published: 2017

47. Search for Extended Sources in the Galactic Plane Using Six Years of Fermi-Large Area Telescope Pass 8 Data above 10 GeV

Author: Gudlaugur Johannesson, Guido Barbiellini, J. W. Hewitt, Daniel Castro, F. de Palma, Claudia Cecchi, Elizabeth C. Ferrara, J. Ballet, Xian Hou, Elisabetta Bissaldi, E. Orlando, F. Loparco, E. Hays, T. A. Porter, Matteo Negro, A. Morselli, Vahé Petrosian, Seth Digel, E. J. Siskind, J. Bregeon, Giacomo Principe, F. Piron, Marco Ajello, Francesco Longo, Nicola Omodei, M.-H. Grondin, Diego F. Torres, G. Tosti, Massimo Persic, J. B. Thayer, Soebur Razzaque, L. Di Venere, J. D. Magill, Giacomo Vianello, Alice K. Harding, Jingcheng Li, Igor V. Moskalenko, Olaf Reimer, D. Horan, Eugenio Bottacini, Alberto Manfreda, M. Lemoine-Goumard, M. Caragiulo, M. N. Mazziotta, S. Maldera, R. Desiante, F. Costanza, T. Kamae, R. Buehler, Denis Bastieri, J. F. Ormes, Ronaldo Bellazzini, Markus Ackermann, K. S. Wood, T. Ohsugi, Eleonora Troja, C. Favuzzi, Peter F. Michelson, Marcello Giroletti, Dario Gasparrini, Carmelo Sgrò, Riccardo Rando, L. Guillemot, M. Di Mauro, T. J. Brandt, F. Spada, Stefan Larsson, M. E. Monzani, C. C. Cheung, S. Cutini, R. Bonino, D. Simone, E. Nuss, T. Reposeur, David Paneque, D. J. Thompson, M. Razzano, Filippo D'Ammando, M. Kuss, I. A. Grenier, D. Malyshev, E. Cavazzuti, David H. Green, Stefano Ciprini, F. Gargano, Eric Charles, Gloria Spandre, J. S. Perkins, D. J. Suson, Elliott D. Bloom, Nicola Giglietto, Matthew Wood, A. Chekhtman, P. Lubrano, Stefan Funk, P. A. Caraveo, G. La Mura, N. Di Lalla, Luca Baldini, Monica Orienti, Sylvain Guiriec, Warit Mitthumsiri, D. Costantin, P. Spinelli, A. Reimer, Francesco Giordano, Melissa Pesce-Rollins, Vaidehi S. Paliya, J. M. Cohen, R. A. Cameron, P. Bruel, Anna Franckowiak, S. Rainò, Tsunefumi Mizuno, G. Chiaro, Yasushi Fukazawa, D. Tak, P. Fusco, S. J. Fegan, ITA, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire Univers et Particules de Montpellier (LUPM), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Leprince-Ringuet (LLR), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Fermi-LAT, Ackermann, M., Ajello, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Bloom, E. D., Bonino, R., Bottacini, E., Brandt, T. J., Bregeon, J., Bruel, P., Buehler, R., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Castro, D., Cavazzuti, E., Cecchi, C., Charles, E., Chekhtman, A., Cheung, C. C., Chiaro, G., Ciprini, S., Cohen, J. M., Costantin, D., Costanza, F., Cutini, S., D'Ammando, F., De Palma, F., Desiante, R., Digel, S. W., Lalla, N. Di, Mauro, M. Di, Venere, L. Di, Favuzzi, C., Fegan, S. J., Ferrara, E. C., Franckowiak, A., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giordano, F., Giroletti, M., Green, D., Grenier, I. A., Grondin, M. -H., Guillemot, L., Guiriec, S., Harding, A. K., Hays, E., Hewitt, J. W., Horan, D., Hou, X., Jóhannesson, G., Kamae, T., Kuss, M., La Mura, G., Larsson, S., Lemoine-Goumard, M., Li, J., Longo, F., Loparco, F., Lubrano, P., Magill, J. D., Maldera, S., Malyshev, D., Manfreda, A., Mazziotta, M. N., Michelson, P. F., Mitthumsiri, W., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Ohsugi, T., Omodei, N., Orienti, M., Orlando, E., Ormes, J. F., Paliya, V. S., Paneque, D., Perkins, J. S., Persic, M., Pesce-Rollins, M., Petrosian, V., Piron, F., Porter, T. A., Principe, G., Raino, S., Rando, R., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Reposeur, T., Sgro, C., Simone, D., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Suson, D. J., Tak, D., Thayer, J. B., Thompson, D. J., Torres, D. F., Tosti, G., Troja, E., Vianello, G., Wood, K. S., Wood, M., Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire AIM, Université Paris Diderot - Paris 7 ( UPD7 ) -Centre d'Etudes de Saclay, Laboratoire Univers et Particules de Montpellier ( LUPM ), Centre National de la Recherche Scientifique ( CNRS ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Université Montpellier 2 - Sciences et Techniques ( UM2 ) -Université de Montpellier ( UM ), Laboratoire Leprince-Ringuet ( LLR ), Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -École polytechnique ( X ) -Centre National de la Recherche Scientifique ( CNRS ), Centre d'Etudes Nucléaires de Bordeaux Gradignan ( CENBG ), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace ( LPC2E ), Centre National de la Recherche Scientifique ( CNRS ) -Université d'Orléans ( UO ) -Institut national des sciences de l'Univers ( INSU - CNRS ), Unité Scientifique de la Station de Nançay ( USN ), and Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS )
Subjects: catalog, [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Astrophysics::High Energy Astrophysical Phenomena, catalogs, gamma rays: general, Astrophysics, 01 natural sciences, gamma ray: energy spectrum, GLAST, Astronomy and Astrophysics, Space and Planetary Science, law.invention, Telescope, law, 0103 physical sciences, 010303 astronomy & astrophysics, Physics, 010308 nuclear & particles physics, Spectral properties, Gamma ray, Function (mathematics), Galactic plane, Astronomy and Astrophysic, Galaxy, [SDU]Sciences of the Universe [physics], gamma ray, spectral, galaxy, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], general [gamma rays], Fermi Gamma-ray Space Telescope, acceptance
Abstract: International audience; The spatial extension of a γ-ray source is an essential ingredient to determine its spectral properties, as well as its potential multiwavelength counterpart. The capability to spatially resolve γ-ray sources is greatly improved by the newly delivered Fermi-Large Area Telescope (LAT) Pass 8 event-level analysis, which provides a greater acceptance and an improved point-spread function, two crucial factors for the detection of extended sources. Here, we present a complete search for extended sources located within 7° from the Galactic plane, using 6 yr of Fermi-LAT data above 10 GeV. We find 46 extended sources and provide their morphological and spectral characteristics. This constitutes the first catalog of hard Fermi-LAT extended sources, named the Fermi Galactic Extended Source Catalog, which allows a thorough study of the properties of the Galactic plane in the sub-TeV domain.
Published: 2017
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48. Modelling energy-dependent pulsar light curves

Author: Constantinos Kalapotharakos, Christo Venter, Monica Barnard, and Alice K. Harding
Subjects: Physics, Energy dependent, High Energy Astrophysical Phenomena (astro-ph.HE), Range (particle radiation), Astrophysics::High Energy Astrophysical Phenomena, Magnetosphere, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Vela, Curvature, Light curve, Pulsar, Space and Planetary Science, Cylinder, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics::Galaxy Astrophysics
Abstract: In recent years, surprise discoveries of pulsed emission from the Crab and Vela pulsars above 100 GeV have drawn renewed attention to this largely unexplored region of the energy range. In this paper, we discuss example light curves due to curvature emission, with good resolution in the different energy bands. Continued light curve modelling may help to discriminate between different emission mechanisms, as well as constrain the location where emission is produced within the pulsar magnetosphere, including regions beyond the light cylinder., Comment: 4 pages, 2 figures, Conference Proceedings IAU Symposium: Pulsar Astrophysics The Next 50 Years
Published: 2017
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49. Discovery of Soft X-Ray Pulsations from PSR J1231–1411 using NICER

Author: Matthew Kerr, Christian Malacaria, Paul S. Ray, Zaven Arzoumanian, John P. Doty, Michael T. Wolff, Scott M. Ransom, Craig B. Markwardt, Slavko Bogdanov, Keith C. Gendreau, Sebastien Guillot, Yang Soong, Alice K. Harding, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Flux, Hot spot (veterinary medicine), Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, X-rays: general, 01 natural sciences, 7. Clean energy, stars: neutron, Millisecond pulsar, 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Soft x ray, Astronomy and Astrophysics, gamma rays: general, Thermal emission, Pulse (physics), pulsars: individual, Neutron star, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Fermi Gamma-ray Space Telescope
Abstract: We report the discovery of soft X-ray pulsations from the nearby millisecond pulsar PSR J1231$-$1411 using NICER. The pulsed emission is characterized by a broad and asymmetric main pulse and a much fainter secondary interpulse, with a total pulsed count rate of 0.055 c s$^{-1}$ in the 0.35-1.5 keV band. We analyzed Fermi LAT data to update the pulse timing model covering 10 years of data and used that model to coherently combine NICER data over a year of observations. Spectral modeling suggests that the flux is dominated by thermal emission from a hot spot (or spots) on the neutron star surface. The phase relationship between the X-ray pulse and the radio and $\gamma$ rays provides insight into the geometry of the system., Comment: ApJ Letters, in press
Published: 2019
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50. Pulsar Polar Cap and Slot Gap Models: Confronting Fermi Data

Author: Alice K. Harding
Subjects: Physics, lcsh:Astronomy, Strong gravity, Astrophysics::High Energy Astrophysical Phenomena, General Physics and Astronomy, Astronomy, Acceleration (differential geometry), Astrophysics, gamma-rays, Light curve, law.invention, Telescope, Particle acceleration, lcsh:QB1-991, Theory of relativity, Pulsar, law, pulsars, General Earth and Planetary Sciences, Fermi Gamma-ray Space Telescope
Abstract: Rotation-powered pulsars are excellent laboratories for studying particle acceleration as well as fundamental physics of strong gravity, strong magnetic fields and relativity. Particle acceleration and high-energy emission from the polar caps is expected to occur in connection with electron-positron pair cascades. I will review acceleration and gamma-ray emission from the pulsar polar cap and associated slot gap. Predictions of these models can be tested with the data set on pulsars collected by the Large Area Telescope on the Fermi Gamma-Ray Telescope over the last four years, using both detailed light curve fitting, population synthesis and phase-resolved spectroscopy.
Published: 2013

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