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101. High-time-resolution Measurements of the Polarization of the Crab Pulsar at 1.38 GHz

Author

B. W. Stappers, Ronald F. Elsner, Alice K. Harding, Agnieszka Slowikowska, Stephen L. O'Dell, Martin C. Weisskopf, Alexander J. van der Horst, and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Crab Pulsar, Linear polarization, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Approx, Position angle, Polarization (waves), Astrophysics - Astrophysics of Galaxies, Quadratic variation, Radio telescope, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Atomic physics, Astrophysics - High Energy Astrophysical Phenomena, Circular polarization
Abstract

Using the Westerbork Synthesis Radio Telescope (WSRT), we obtained high-time-resolution measurements of the full (linear and circular) polarization of the Crab pulsar. Taken at a resolution of 1/8192 of the 34-ms pulse period (i.e., $4.1~\mu{\rm s}$), the 1.38-GHz linear-polarization measurements are in general agreement with previous lower-time-resolution 1.4-GHz measurements of linear polarization in the main pulse (MP), in the interpulse (IP), and in the low-frequency component (LFC). We find the MP and IP to be linearly polarized at about $24\%$ and $21\%$, with no discernible difference in polarization position angle. However, and contrary to theoretical expectations and measurements in the visible, we find no evidence for significant variation (sweep) in polarization position angle over the MP, the IP, or the LFC. Although, the main pulse exhibits a small but statistically significant quadratic variation in the degree of linear polarization. We discuss the implications which appear to be in contradiction to theoretical expectations. In addition, we detect weak circular polarization in the main pulse and interpulse, and strong ($\approx 20\%$) circular polarization in the low-frequency component, which also exhibits very strong ($\approx 98\%$) linear polarization at a position angle about $40\degree$ from that of the MP or IP. The pulse-mean polarization properties are consistent with the LFC being a low-altitude component and the MP and IP being high-altitude caustic components. Nevertheless, current models for the MP and IP emission do not readily account for the observed absence of pronounced polarization changes across the pulse. Finally, we measure IP and LFC pulse phases relative to the MP that are consistent with recent measurements, which have shown that the phases of these pulse components are evolving with time., Comment: 28 pages, 10 figures, accepted by the Astrophysical Journal

Published
2015

102. Discovery of Gamma-ray Pulsations from the Transitional Redback PSR J1227-4853

Author

Matthew Kerr, Paul S. Ray, Fernando Camilo, Stanislav Fort, Alice K. Harding, Jayanta Roy, Ben Stappers, Holger J. Pletsch, Bhaswati Bhattacharyya, C. C. Cheung, Tyrel J. Johnson, and J. Deneva

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::High Energy Astrophysical Phenomena, Flux, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Light curve, Orbital period, law.invention, Telescope, Pulsar, Space and Planetary Science, Millisecond pulsar, law, Binary star, Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract

The 1.69 ms spin period of PSR J1227-4853 was recently discovered in radio observations of the low-mass X-ray binary XSS J12270-4859 following the announcement of a possible transition to a rotation-powered millisecond pulsar state, inferred from decreases in optical, X-ray, and gamma-ray flux from the source. We report the detection of significant (5$\sigma$) gamma-ray pulsations after the transition, at the known spin period, using ~1 year of data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The gamma-ray light curve of PSR J1227-4853 can be fit by one broad peak, which occurs at nearly the same phase as the main peak in the 1.4 GHz radio profile. The partial alignment of light-curve peaks in different wavebands suggests that at least some of the radio emission may originate at high altitude in the pulsar magnetosphere, in extended regions co-located with the gamma-ray emission site. We folded the LAT data at the orbital period, both pre- and post-transition, but find no evidence for significant modulation of the gamma-ray flux. Analysis of the gamma-ray flux over the mission suggests an approximate transition time of 2012 November 30. Continued study of the pulsed emission and monitoring of PSR J1227-4853, and other known redback systems, for subsequent flux changes will increase our knowledge of the pulsar emission mechanism and transitioning systems., Comment: 5 figures, 1 table, accepted for publication in ApJ, updated to reflect accepted version and add additional coauthor

Published
2015

103. On the polar cap cascade pair multiplicity of young pulsars

Author

Andrey Timokhin and Alice K. Harding

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Parameter space, Curvature, Magnetic field, Particle acceleration, Pair production, Pulsar, Space and Planetary Science, Cascade, Multiplicity (chemistry), Astrophysics - High Energy Astrophysical Phenomena
Abstract

We study the efficiency of pair production in polar caps of young pulsars under a variety of conditions to estimate the maximum possible multiplicity of pair plasma in pulsar magnetospheres. We develop a semi-analytic model for calculation of cascade multiplicity which allows efficient exploration of the parameter space and corroborate it with direct numerical simulations. Pair creation processes are considered separately from particle acceleration in order to assess different factors affecting cascade efficiency, with acceleration of primary particles described by recent self-consistent non-stationary model of pair cascades. We argue that the most efficient cascades operate in the curvature radiation/synchrotron regime, the maximum multiplicity of pair plasma in pulsar magnetospheres is ~few x 10^5. The multiplicity of pair plasma in magnetospheres of young energetic pulsars weakly depends on the strength of the magnetic field and the radius of curvature of magnetic field lines and has a stronger dependence on pulsar inclination angle. This result questions assumptions about very high pair plasma multiplicity in theories of pulsar wind nebulae., Comment: 27 pages, 23 figures; ApJ, 810, 144 (2015)

Published
2015
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104. Discovery of a Spin-Down State Change in the LMC Pulsar B0540-69

Author

Lucas Guillemot, Pierrick Martin, F. E. Marshall, Alice K. Harding, David Smith, GSFC Astrophysics Science Division, NASA Goddard Space Flight Center (GSFC), 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), 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)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), 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), 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 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), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), 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), and 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)

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::High Energy Astrophysical Phenomena, Spin rate, Magnetosphere, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Pulsar, 13. Climate action, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, Large Magellanic Cloud, Spin-½
Abstract

We report the discovery of a large, sudden, and persistent increase in the spin-down rate of B0540-69, a young pulsar in the Large Magellanic Cloud, using observations from the Swift and RXTE satellites. The relative increase in the spin-down rate of 36% is unprecedented for B0540-69. No accompanying change in the spin rate is seen, and no change is seen in the pulsed X-ray emission from B0540-69 following the change in the spin-down rate. Such large relative changes in the spin-down rate are seen in the recently discovered class of 'intermittent pulsars', and we compare the properties of B0540-69 to such pulsars. We consider possible changes in the magnetosphere of the pulsar that could cause such a large change in the spin-down rate., Comment: 6 pages, 2 figures, accepted for publication in ApJ Letters

Published
2015
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105. PSR J1906+0722: An Elusive Gamma-ray Pulsar

Author

R. Desiante, A. De Angelis, Eric Charles, D. J. Suson, C. Cecchi, Carmelo Sgrò, Riccardo Rando, Pablo Torne, Giacomo Vianello, R. Bonino, M. Orienti, Johann Cohen-Tanugi, S. Cutini, A. S. Johnson, Denis Bastieri, P. Fusco, Xian Hou, Alice K. Harding, F. de Palma, Francesco Longo, R. Claus, Michael Kramer, C. Aulbert, Ronaldo Bellazzini, F. Krauss, F. Loparco, T. Glanzman, A. Morselli, A. Franckowiak, Dario Gasparrini, David Champion, T. Jogler, H. Fehrmann, S. Murgia, G. A. Caliandro, Hiromitsu Takahashi, J. Li, Frederic Piron, Sylvain Guiriec, Martino Marelli, B. Machenschalk, Eleonora Troja, M. Yassine, M. Caragiulo, P. M. Saz Parkinson, J. Chiang, A. B. Hill, Michael Mayer, M. Schaal, S. Rainò, Tsunefumi Mizuno, A. Reimer, P. Spinelli, M. Kuss, W. B. Focke, O. Bock, G. Chiaro, Jean Ballet, A. Cuéllar, J. E. Grove, F. Spada, Holger J. Pletsch, Stefano Ciprini, T. J. Brandt, H. Laffon, John W. Hewitt, Elizabeth C. Ferrara, L. Latronico, Nicola Giglietto, Francesco Giordano, Benjamin William Allen, M. E. Monzani, Diego F. Torres, G. Pivato, Matthew Wood, Elena Orlando, J. B. Thayer, C. Favuzzi, E. J. Siskind, Pascal Bruel, M. Razzano, Gloria Spandre, P. A. Caraveo, A. Schulz, Filippo D'Ammando, Eugenio Bottacini, Persis S. Drell, Elizabeth Hays, Alberto Manfreda, Peter F. Michelson, M. N. Mazziotta, Elisabetta Bissaldi, L. Tibaldo, P. Lubrano, D. Paneque, S. Buson, F. Gargano, Gudlaugur Johannesson, H.-B. Eggenstein, J. Wu, Lucas Guillemot, Liang Li, Guido Barbiellini, R. A. Cameron, Eric Nuss, I. A. Grenier, T. Ohsugi, M. Ackermann, G. Godfrey, Gino Tosti, K. S. Wood, Igor V. Moskalenko, D. Horan, Johan Bregeon, C. J. Clark, Stefan Larsson, M. N. Lovellette, Melissa Pesce-Rollins, Luca Baldini, A. Chekhtman, 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, 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), 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)-Centre National de la Recherche Scientifique (CNRS), 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 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 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), 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), Clark, C. J., Pletsch, H. J., Wu, J., Guillemot, L., Ackermann, M., Allen, B., De Angelis, A., Aulbert, C., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Bock, O., Bonino, R., Bottacini, E., Brandt, T. J., Bregeon, J., Bruel, P., Buson, S., Caliandro, G. A., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Cecchi, C., Champion, D. J., Charles, E., Chekhtman, A., Chiang, J., Chiaro, G., Ciprini, S., Claus, R., Cohen Tanugi, J., Cuéllar, A., Cutini, S., D'Ammando, F., Desiante, R., Drell, P. S., Eggenstein, H. B., Favuzzi, C., Fehrmann, H., Ferrara, E. C., Focke, W. B., Franckowiak, A., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giordano, F., Glanzman, T., Godfrey, G., Grenier, I. A., Grove, J. E., Guiriec, S., Harding, A. K., Hays, E., Hewitt, J. W., Hill, A. B., Horan, D., Hou, X., Jogler, T., Johnson, A. S., Jóhannesson, G., Kramer, M., Krauss, F., Kuss, M., Laffon, H., Larsson, S., Latronico, L., Li, J., Li, L., Longo, Francesco, Loparco, F., Lovellette, M. N., Lubrano, P., Machenschalk, B., Manfreda, A., Marelli, M., Mayer, M., Mazziotta, M. N., Michelson, P. F., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Nuss, E., Ohsugi, T., Orienti, M., Orlando, E., Palma, F. De, Paneque, D., Pesce Rollins, M., Piron, F., Pivato, G., Rainò, S., Rando, R., Razzano, M., Reimer, A., Parkinson, P. M. Saz, Schaal, M., Schulz, A., Sgrò, C., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Suson, D. J., Takahashi, H., Thayer, J. B., Tibaldo, L., Torne, P., Torres, D. F., Tosti, G., Troja, E., Vianello, G., Wood, K. S., Wood, M., Yassine, Manal, 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), 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), 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)-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), 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 de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Clark CJ, Pletsch HJ, Wu J, Guillemot L, Ackermann M, Allen B, de Angelis A, Aulbert C, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bellazzini R, Bissaldi E, Bock O, Bonino R, Bottacini E, Brandt TJ, Bregeon J, Bruel P, Buson S, Caliandro GA, Cameron RA, Caragiulo M, Caraveo PA, Cecchi C, Champion DJ, Charles E, Chekhtman A, Chiang J, Chiaro G, Ciprini S, Claus R, Cohen-Tanugi J, Cuellar A, Cutini S, DAmmando F, Desiante R, Drell PS, Eggenstein HB, Favuzzi C, Fehrmann H, Ferrara EC, Focke WB, Franckowiak A, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giordano F, Glanzman T, Godfrey G, Grenier IA, Grove JE, Guiriec S, Harding AK, Hays E, Hewitt JW, Hill AB, Horan D, Hou X, Jogler T, Johnson AS, Johannesson G, Kramer M, Krauss F, Kuss M, Laffon H, Larsson S, Latronico L, Li J, Li L, Longo F, Loparco F, Lovellette MN, Lubrano P, Machenschalk B, Manfreda A, Marelli M, Mayer M, Mazziotta MN, Michelson PF, Mizuno T, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nuss E, Ohsugi T, Orienti M, Orlando E, de Palma F, Paneque D, Pesce-Rollins M, Piron F, Pivato G, Raino S, Rando R, Razzano M, Reimer A, Parkinson PMS, Schaal M, Schulz A, Sgro C, Siskind EJ, Spada F, Spandre G, Spinelli P, Suson DJ, Takahashi H, Thayer JB, Tibaldo L, Torne P, Torres DF, Tosti G, Troja E, Vianello G, Wood KS, Wood M, and Yassine M

Subjects
gamma rays: stars, pulsars: individual: PSR J1906+0722, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Flux, Astrophysics, star [gamma rays], law.invention, Gamma rays: stars, Telescope, Pulsar, law, individual (PSR J1906+0722) [pulsars], Supernova remnant, Astrophysics::Galaxy Astrophysics, Spin-½, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, [PHYS]Physics [physics], Molecular cloud, Gamma ray, Astronomy and Astrophysics, Space and Planetary Science, ddc:520, pulsars: individual (PSR J1906+0722), Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], gamma rays: stars, Fermi Gamma-ray Space Telescope
Abstract

We report the discovery of PSR J1906+0722, a gamma-ray pulsar detected as part of a blind survey of unidentified Fermi Large Area Telescope (LAT) sources being carried out on the volunteer distributed computing system, Einstein@Home. This newly discovered pulsar previously appeared as the most significant remaining unidentified gamma-ray source without a known association in the second Fermi-LAT source catalog (2FGL) and was among the top ten most significant unassociated sources in the recent third catalog (3FGL). PSR J1906+0722 is a young, energetic, isolated pulsar, with a spin frequency of $8.9$ Hz, a characteristic age of $49$ kyr, and spin-down power $1.0 \times 10^{36}$ erg s$^{-1}$. In 2009 August it suffered one of the largest glitches detected from a gamma-ray pulsar ($\Delta f / f \approx 4.5\times10^{-6}$). Remaining undetected in dedicated radio follow-up observations, the pulsar is likely radio-quiet. An off-pulse analysis of the gamma-ray flux from the location of PSR J1906+0722 revealed the presence of an additional nearby source, which may be emission from the interaction between a neighboring supernova remnant and a molecular cloud. We discuss possible effects which may have hindered the detection of PSR J1906+0722 in previous searches and describe the methods by which these effects were mitigated in this survey. We also demonstrate the use of advanced timing methods for estimating the positional, spin and glitch parameters of difficult-to-time pulsars such as this., Comment: 7 pages, 4 figures, accepted for publication in Astrophysical Journal Letters

Published
2015
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106. Developing Radio Beam Geometry and Luminosity Models of Pulsars

Author

Alice K. Harding, Peter L. Gonthier, Sarah A. Story, R. A. Arevalo, and B. M. Giacherio

Subjects
Physics, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, Magnetic dip, Astronomy and Astrophysics, Astrophysics, Position angle, 01 natural sciences, Pulse (physics), Luminosity, Core (optical fiber), Pulsar, Space and Planetary Science, 0103 physical sciences, Single-core, Limit (mathematics), 010306 general physics, 010303 astronomy & astrophysics
Abstract

Our recent studies of pulsar population statistics suggest that improvements of radio and gamma-ray beam geometry and luminosity models require further refinement. The goal of this project is to constrain the viewing geometry for some radio pulsars, especially three-peaked pulse profiles, in order to limit the uncertainty of the magnetic inclination and impact angles. We perform fits of the pulse profile and position angle sweep of radio pulsars for the available frequencies. We assume a single core and conal beams described by Gaussians. We incorporate three different size cones with frequency dependence from the work of Mitra & Deshpande (1999). We obtain separate spectral indices for the core and cone beams and explore the trends of the ratio of core to cone peak fluxes. This ratio is observed to have some dependence with period. However, we cannot establish the suggested functional form of this ratio as indicated by the work of Arzoumanian, Chernoff & Cordes (2002).

Published
2006
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107. Pulsar Slot Gaps and Unidentified Egret Sources

Author

Alice K. Harding and Alexander G. Muslimov

Subjects
Physics, biology, Field line, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), Solid angle, FOS: Physical sciences, Flux, Astronomy and Astrophysics, Astrophysics, biology.organism_classification, Viewing angle, Neutron star, Pulsar, Space and Planetary Science, Egret, Line (formation)
Abstract

A new picture of pulsar high-energy emission is proposed that is different from both the traditional polar cap and outer gap models, but combines elements of each. The slot gap model is based on electron acceleration along the edge of the open field region from the neutron star surface to near the light cylinder. Along the last open field line, the pair formation front rises to very high altitude forming a slot gap, where the accelerating electric field is unscreened by pairs. The resulting radiation features both hollow cones from the lower-altitude pair cascades, seen at small viewing angles, as well as caustic emission on the trailing-edge field lines at high altitude, seen from both poles at large viewing angle. The combination of the small solid angle of slot gap emission (<< 1 sr) with a high probability of viewing the emission predicts that more gamma-ray pulsars could be detected at larger distances. In this picture, many of the positional coincidences of radio pulsars with unidentified EGRET sources become plausible as real associations, as the flux predicted by the slot gap model for many of the pulsars would provide the observed EGRET source flux. The expected probability of seeing radio-quiet gamma-ray pulsars in this model will also be discussed., 10 pages, 4 figures, to appear in proceedings of "The Multiwavelength Approach to Unidentified Sources", ed. G. Romero & K.S. Cheng

Published
2005
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109. Rotational Sweepback of Magnetic Field Lines in Geometric Models of Pulsar Radio Emission

Author

Alice K. Harding and Jaroslaw Dyks

Subjects
Physics, Plane (geometry), Astrophysics (astro-ph), FOS: Physical sciences, Astronomy and Astrophysics, Context (language use), Astrophysics, Radius, Position angle, Rotation, Magnetic field, Dipole, Space and Planetary Science, Cylinder, Atomic physics
Abstract

We study the rotational distortions of the vacuum dipole magnetic field in the context of geometrical models of the radio emission from pulsars. We find that at low altitudes the rotation deflects the local direction of the magnetic field by at most an angle of the order of r_n^2, where r_n = r/Rlc, r is the radial distance of the radio emission and Rlc is the light cylinder radius. To the second order in r_n, this distortion is symmetrical with respect to the plane containing the dipole axis and the rotation axis (Omega-mu plane). The lowest order distortion which is asymmetrical with respect to the Omega-mu plane is third order in r_n. We show, however, that the influence of the sweepback on the outer boundary of the open field line region (open volume) is a much larger effect, of the order of r_n^1/2. The open volume is shifted backwards with respect to the rotation direction by an angle delta_ov ~ 0.2 sin(alpha) r_n^1/2 where alpha is the dipole inclination with respect to the rotation axis. The associated phase shift of the pulse profile Delta_phi_ov ~ 0.2 r_n^1/2 can easily exceed the shift due to combined effects of aberration and propagation time delays (=~ 2r_n). This strongly affects the misalignment of the center of the PA curve and the center of the pulse profile, thereby modifying the delay-radius relation. Contrary to intuition, the effect of sweepback dominates over other effects when emission occurs at low altitudes. For r_n, Comment: 29 pages, 7 figures, submitted to ApJ

Published
2004
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110. Relativistic Effects and Polarization in Three High‐Energy Pulsar Models

Author

Jaroslaw Dyks, Alice K. Harding, and Bronislaw Rudak

Subjects
Physics, Crab Pulsar, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), FOS: Physical sciences, Astronomy and Astrophysics, Optical polarization, Astrophysics, Polarization (waves), Position angle, Superposition principle, Pulsar, Space and Planetary Science, Degree of polarization, Relativistic quantum chemistry
Abstract

We present the influence of the special relativistic effects of aberration and light travel time delay on pulsar high-energy lightcurves and polarization characteristics predicted by three models: the two-pole caustic model, the outer gap model, and the polar cap model. Position angle curves and degree of polarization are calculated for the models and compared with the optical data on the Crab pulsar. The relative positions of peaks in gamma-ray and radio lightcurves are discussed in detail for the models. We find that the two-pole caustic model can reproduce qualitatively the optical polarization characteristics of the Crab pulsar - fast swings of the position angle and minima in polarization degree associated with both peaks. The anticorrelation between the observed flux and the polarization degree (observed in the optical band also for B0656+14) naturally results from the caustic nature of the peaks which are produced in the model due to the superposition of radiation from many different altitudes, ie. polarized at different angles. The two-pole caustic model also provides an acceptable interpretation of the main features in the Crab's radio profile. Neither the outer gap model nor the polar cap model are able to reproduce the optical polarization data on the Crab. Although the outer gap model is very successful in reproducing the relative positions of gamma-ray and radio peaks in pulse profiles, it can reproduce the high-energy lightcurves only when photon emission from regions very close to the light cylinder is included., Comment: 49 pages, 14 figures, 1 table, submitted to ApJ

Published
2004
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111. Role of Beam Geometry in Population Statistics and Pulse Profiles of Radio and Gamma‐Ray Pulsars

Author

Alice K. Harding, Robert Van Guilder, and Peter L. Gonthier

Subjects
Physics, biology, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), Gamma ray, FOS: Physical sciences, Astronomy and Astrophysics, Beam geometry, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, biology.organism_classification, 01 natural sciences, Pulse (physics), Magnetic field, Pulsar, Space and Planetary Science, 0103 physical sciences, Egret, Sensitivity (control systems), 010306 general physics, 010303 astronomy & astrophysics, Beam (structure)
Abstract

We present results of a pulsar population synthesis study that incorporates a number of recent developments and some significant improvements over our previous study. We have included the results of the Parkes multi-beam pulsar survey in our select group of nine radio surveys, doubling our sample of radio pulsars. We adopted with some modifications the radio beam geometry of Arzoumanian, Chernoff & Cordes (2002). For the $\gamma$-ray beam, we have assumed the slot gap geometry described in the work of Muslimov & Harding (2003). To account for the shape of the distribution of radio pulsars in the $\dot P-P$ diagram, we continue to find that decay of the magnetic field on a timescale of 2.8 Myr is needed. With all nine surveys, our model predicts that EGRET should have seen 7 radio-quiet (below the sensitivity of these radio surveys) and 19 radio-loud $\gamma$-ray pulsars. AGILE (nominal sensitivity map) is expected to detect 13 radio-quiet and 37 radio-loud $\gamma$-ray pulsars, while GLAST, with greater sensitivity is expected to detect 276 radio-quiet and 344 radio-loud $\gamma$-ray pulsars. When the Parkes multi-beam pulsar survey is excluded, the ratio of radio-loud to radio-quiet $\gamma$-ray pulsars decreases, especially for GLAST. The decrease for EGRET is 45%, implying that some fraction of EGRET unidentified sources are radio-loud $\gamma$-ray pulsars. In the radio geometry adopted, short period pulsars are core dominated. Unlike the EGRET $\gamma$-ray pulsars, our model predicts that when two $\gamma$-ray peaks appear in the pulse profile, a dominant radio core peak appears in between the $\gamma$-ray peaks. Our findings suggest that further improvements are required in describing both the radio and $\gamma$-ray geometries., Comment: 39 pages, 13 eps figures, accepted for publication in ApJ, April 1, 2004

Published
2004
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112. Pulsar populations and unidentified γ-ray sources

Author

I.A. Grenier, Alice K. Harding, Peter L. Gonthier, and C.A. Perrot

Subjects
Atmospheric Science, Astrophysics::High Energy Astrophysical Phenomena, Population, FOS: Physical sciences, Aerospace Engineering, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, law.invention, Telescope, Pulsar, Observatory, law, Egret, education, Astrophysics::Galaxy Astrophysics, Physics, education.field_of_study, biology, Astrophysics (astro-ph), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Astronomy and Astrophysics, Galactic plane, biology.organism_classification, Galaxy, Geophysics, Space and Planetary Science, General Earth and Planetary Sciences, X-ray pulsar
Abstract

The EGRET telescope on the Compton Gamma-Ray Observatory detected over 200 sources and the majority of these are still unidentified. At least three subpopulations of EGRET sources have been associated with the Galaxy: bright sources lying along the Galactic plane, weaker sources spatially correlated with the Gould Belt and a high-latitude, halo population. Many of these sources may be pulsars and there are more than two-dozen radio pulsars in or near EGRET source error boxes, most of them recently discovered in the Parkes Multibeam Survey. We present results from several population synthesis studies of pulsars in the Galaxy, which predict the number of pulsars detected by gamma-ray and radio surveys assuming models for the high-energy emission beam and its relation to the radio beam. Future gamma-ray pulsar detections by AGILE and GLAST together with the recent large rise in the radio pulsar population will give greatly improved statistics. The relative numbers of radio and gamma-ray pulsars detected in the plane and in the Gould Belt populations will provide an important discriminator between models of high-energy emission and will profoundly affect the numbers and birth rate of pulsars in the Galaxy., 6 Pages, 3 Figures, to be published in proceedings of 34th COSPAR Scientific Assembly, Symposium on Supernova Remnants and Neutron Stars

Published
2004
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113. Regimes of Pulsar Pair Formation and Particle Energetics

Author

Alexander G. Muslimov, Alice K. Harding, and Bing Zhang

Subjects
Physics, education.field_of_study, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), Population, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Acceleration voltage, Particle acceleration, Stars, Neutron star, Pair production, Pulsar, Space and Planetary Science, Millisecond pulsar, education
Abstract

We investigate the conditions required for the production of electron-positron pairs above a pulsar polar cap (PC) and the influence of pair production on the energetics of the primary particle acceleration. Assuming space-charge limited flow acceleration including the inertial frame-dragging effect, we allow both one-photon and two-photon pair production by either curvature radiation (CR) photons or photons resulting from inverse-Compton scattering of thermal photons from the PC by primary electrons. We find that, while only the younger pulsars can produce pairs through CR, nearly all known radio pulsars are capable of producing pairs through non-resonant inverse-Compton scatterings. The effect of the neutron star equations of state on the pair death lines is explored. We show that pair production is facilitated in more compact stars and more massive stars. Therefore accretion of mass by pulsars in binary systems may allow pair production in most of the millisecond pulsar population. We also find that two-photon pair production may be important in millisecond pulsars if their surface temperatures are above about three million degrees K. Pulsars that produce pairs through CR will have their primary acceleration limited by the effect of screening of the electric field. In this regime, the high-energy luminosity should follow a $L_{HE} \propto \dot E_{rot}^{1/2}$ dependence. The acceleration voltage drop in pulsars that produce pairs only through inverse-Compton emission will not be limited by electric field screening. In this regime, the high-energy luminosity should follow a $L_{HE} \propto \dot E_{rot}$ dependence. Thus, older pulsars will have significantly lower gamma-ray luminosity., 22 pages, 4 figures, accepted for publication in Astrophysical Journal

Published
2002
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114. Multiwavelength Polarization of Rotation-powered Pulsars

Author

Constantinos Kalapotharakos and Alice K. Harding

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Synchrotron radiation, Magnetosphere, Astronomy and Astrophysics, Radiation, Polarization (waves), Curvature, Position angle, 01 natural sciences, Computational physics, Current sheet, Pulsar, Space and Planetary Science, 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics
Abstract

Polarization measurements provide strong constraints on models for emission from rotation-powered pulsars. We present multiwavelength polarization predictions showing that measurements over a range of frequencies can be particularly important for constraining the emission location, radiation mechanisms and system geometry. The results assume a generic model for emission from the outer magnetosphere and current sheet in which optical to hard X-ray emission is produced by synchrotron radiation from electron-positron pairs and gamma-ray emission is produced by curvature radiation or synchrotron radiation from accelerating primary electrons. The magnetic field structure of a force-free magnetosphere is assumed and the phase-resolved and phase-averaged polarization is calculated in the frame of an inertial observer. We find that large position angle swings and deep depolarization dips occur during the light curve peaks in all energy bands. For synchrotron emission, the polarization characteristics are strongly dependent on photon emission radius with larger, nearly $180^\circ$, position angle swings for emission outside the light cylinder as the line-of-sight crosses the current sheet. The phase-averaged polarization degree for synchrotron radiation is less that 10% and around 20% for emission starting inside and outside the light cylinder respectively, while the polarization degree for curvature radiation is much larger, up to 40% - 60%. Observing a sharp increase in polarization degree and a change in position angle at the transition between X-ray and gamma-ray spectral components would indicate that curvature radiation is the gamma-ray emission mechanism., 23 pages, 7 figures, accepted for publication in Astrophysical Journal

Published
2017
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115. The Contribution of Millisecond Pulsars to the Galactic Cosmic-Ray Lepton Spectrum

Author

Alice K. Harding, A. Kopp, Christo Venter, Peter L. Gonthier, and I. Büsching

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Atmospheric Science, education.field_of_study, Astrophysics::High Energy Astrophysical Phenomena, Population, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Aerospace Engineering, Astronomy, Astronomy and Astrophysics, Cosmic ray, Astrophysics, Galaxy, Supernova, Geophysics, Pair production, Pulsar, Space and Planetary Science, Millisecond pulsar, General Earth and Planetary Sciences, education, Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract

Pulsars are believed to be sources of relativistic electrons and positrons. The abundance of detections of gamma-ray millisecond pulsars by Fermi Large Area Telescope coupled with their light curve characteristics that imply copious pair production in their magnetospheres, motivated us to investigate this old pulsar population as a source of Galactic electrons and positrons and their contribution to the enhancement in cosmic-ray positron flux at GeV energies. We use a population synthesis code to predict the source properties (number, position, and power) of the present-day Galactic millisecond pulsars, taking into account the latest Fermi and radio observations to calibrate the model output. Next, we simulate pair cascade spectra from these pulsars using a model that invokes an offset-dipole magnetic field. We assume free escape of the pairs from the pulsar environment. We then compute the cumulative spectrum of transported electrons and positrons at Earth, following their diffusion and energy losses as they propagate through the Galaxy. Our results indicate that the predicted particle flux increases for non-zero offsets of the magnetic polar caps. Comparing our predicted spectrum and positron fraction to measurements by AMS-02, PAMELA, and Fermi, we find that millisecond pulsars are only modest contributors at a few tens of GeV, after which this leptonic spectral component cuts off. The positron fraction is therefore only slightly enhanced above 10 GeV relative to a background flux model. This implies that alternative sources such as young, nearby pulsars and supernova remnants should contribute additional primary positrons within the astrophysical scenario., 19 pages, 3 figures, accepted for publication in Advances in Space Research

Published
2014

116. Fermi-LAT Observations of the Gamma-Ray Burst GRB 130427A

Author

P. A. Jenke, Brian L Winer, Soebur Razzaque, A. A. Moiseev, L. R. Cominsky, Igor V. Moskalenko, Melissa Gibby, Yoshiyuki Inoue, Justin D. Finke, Olaf Reimer, Katsuaki Asano, Robert D. Preece, F. Loparco, E. Moretti, André Schulz, Akira Okumura, George Younes, Matthew G. Baring, D. Byrne, William S. Paciesas, Chryssa Kouveliotou, C. Favuzzi, Judith Racusin, Melissa Pesce-Rollins, Charles A. Meegan, Robert R. Rando, T. Jogler, S. J. Fegan, Luca Baldini, J. G. Thayer, W. B. Focke, P. Spinelli, Sylvain Guiriec, Ryo Yamazaki, P. N. Bhat, Alex Drlica-Wagner, Shuze Zhu, A. von Kienlin, Vandiver Chaplin, Francesco Giordano, Anne M. Diekmann, M. E. Monzani, Jean Ballet, T. A. Porter, Hoi-Fung Yu, A. Franckowiak, J. Michael Burgess, G. Godfrey, W. N. Johnson, W. B. Atwood, Nicola Omodei, S. Rainò, Jeffrey D. Scargle, J. R. Cummings, J. S. Perkins, R. A. Cameron, Tsunefumi Mizuno, R. E. Hughes, Denis Bastieri, Misty Giles, Nicola Giglietto, Rodrigo Nemmen, Shaolin Xiong, Stefano Ciprini, D. Hadasch, S. Germani, K. S. Wood, T. Ohsugi, Eleonora Troja, Stefan Funk, Colleen A. Wilson-Hodge, P. Bruel, G. Chiaro, D. Horan, F. de Palma, A. C. Collazzi, Julie McEnery, V. Pelassa, A. J. van der Horst, Neil Gehrels, L. Di Venere, David Gruber, J. E. Grove, Yasushi Fukazawa, E. J. Siskind, Hiromitsu Takahashi, Valerie Connaughton, A. De Angelis, Adam Goldstein, M. Mayer, V. La Parola, D. J. Thompson, Carmelo Sgrò, G. Tosti, M. N. Lovellette, P. A. Caraveo, Persis S. Drell, M. Roth, Gudlaugur Johannesson, D. Kocevski, V. Vasileiou, Marco Ajello, J. B. Thayer, J. Lande, Jonathan Granot, S. Murgia, P. Fusco, E. Nuss, David Paneque, Sheila McBreen, M. Kuss, T. L. Usher, Francesco Longo, S. Buson, F. Piron, Giacomo Vianello, Masanori Ohno, Felix Ryde, W. H. Cleveland, Emanuele Bonamente, Charles D. Dermer, Magnus Axelsson, Alice K. Harding, I. A. Grenier, Markus Ackermann, Justin Vandenbroucke, Michael S. Briggs, Vahé Petrosian, Luca Latronico, Jürgen Knödlseder, Gloria Spandre, P. M. Saz Parkinson, Ronaldo Bellazzini, Johann Cohen-Tanugi, R. Desiante, T. Kawano, M. Tinivella, Elizabeth C. Ferrara, Guido Barbiellini, Stephen F. Foley, G. A. Caliandro, C. C. Cheung, M. Deklotz, Elisabetta Bissaldi, E. Hays, A. Morselli, F. Gargano, M. Orienti, V. Vitale, J. Bregeon, R. Claus, Alberto Sartori, Y. Hanabata, L. Tibaldo, G. Pivato, A. Reimer, M. Brigida, D. Tierney, M. N. Mazziotta, Eda Sonbas, Arne Rau, Giancarlo Cusumano, Claudia Cecchi, S. Larsson, Diego F. Torres, Gerard Fitzpatrick, S. Cutini, R. M. Kippen, James Chiang, M. Hayashida, Hiroyasu Tajima, Jan Conrad, R. Buehler, Peter F. Michelson, Marcello Giroletti, Eric Charles, Steven Ritz, A. Chekhtman, P. Lubrano, Keith Bechtol, M. Razzano, Filippo D'Ammando, Ackermann M, Ajello M, Asano K, Atwood WB, Axelsson M, Baldini L, Ballet J, Barbiellini G, Baring MG, Bastieri D, Bechtol K, Bellazzini R, Bissaldi E, Bonamente E, Bregeon J, Brigida M, Bruel P, Buehler R, Burgess JM, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Cecchi C, Chaplin V, Charles E, Chekhtman A, Cheung CC, Chiang J, Chiaro G, Ciprini S, Claus R, Cleveland W, Cohen-Tanugi J, Collazzi A, Cominsky LR, Connaughton V, Conrad J, Cutini S, DAmmando F, de Angelis A, DeKlotz M, de Palma F, Dermer CD, Desiante R, Diekmann A, Di Venere L, Drell PS, Drlica-Wagner A, Favuzzi C, Fegan SJ, Ferrara EC, Finke J, Fitzpatrick G, Focke WB, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gehrels N, Germani S, Gibby M, Giglietto N, Giles M, Giordano F, Giroletti M, Godfrey G, Granot J, Grenier IA, Grove JE, Gruber D, Guiriec S, Hadasch D, Hanabata Y, Harding AK, Hayashida M, Hays E, Horan D, Hughes RE, Inoue Y, Jogler T, Johannesson G, Johnson WN, Kawano T, Knodlseder J, Kocevski D, Kuss M, Lande J, Larsson S, Latronico L, Longo F, Loparco F, Lovellette MN, Lubrano P, Mayer M, Mazziotta MN, McEnery JE, Michelson PF, Mizuno T, Moiseev AA, Monzani ME, Moretti E, Morselli A, Moskalenko IV, Murgia S, Nemmen R, Nuss E, Ohno M, Ohsugi T, Okumura A, Omodei N, Orienti M, Paneque D, Pelassa V, Perkins JS, Pesce-Rollins M, Petrosian V, Piron F, Pivato G, Porter TA, Racusin JL, Raino S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Ritz S, Roth M, Ryde F, Sartori A, Parkinson PMS, Scargle JD, Schulz A, Sgro C, Siskind EJ, Sonbas E, Spandre G, Spinelli P, Tajima H, Takahashi H, Thayer JG, Thayer JB, Thompson DJ, Tibaldo L, Tinivella M, Torres DF, Tosti G, Troja E, Usher TL, Vandenbroucke J, Vasileiou V, Vianello G, Vitale V, Winer BL, Wood KS, Yamazaki R, Younes G, Yu HF, Zhu SJ, Bhat PN, Briggs MS, Byrne D, Foley S, Goldstein A, Jenke P, Kippen RM, Kouveliotou C, McBreen S, Meegan C, Paciesas WS, Preece R, Rau A, Tierney D, van der Horst AJ, von Kienlin A, Wilson-Hodge C, Xiong S, Cusumano G, La Parola V, Cummings JR, M., Ackermann, M., Ajello, K., Asano, W. B., Atwood, M., Axelsson, L., Baldini, J., Ballet, BARBIELLINI AMIDEI, Guido, M. G., Baring, D., Bastieri, K., Bechtol, R., Bellazzini, Bissaldi, Elisabetta, E., Bonamente, J., Bregeon, M., Brigida, P., Bruel, R., Buehler, J. M., Burge, S., Buson, G. A., Caliandro, R. A., Cameron, P. A., Caraveo, C., Cecchi, V., Chaplin, E., Charle, A., Chekhtman, C. C., Cheung, J., Chiang, G., Chiaro, S., Ciprini, R., Clau, W., Cleveland, J., Cohen Tanugi, A., Collazzi, L. R., Cominsky, V., Connaughton, J., Conrad, S., Cutini, F., D'Ammando, A. d., Angeli, M., Deklotz, F. d., Palma, C. D., Dermer, R., Desiante, A., Diekmann, L. D., Venere, P. S., Drell, A., Drlica Wagner, C., Favuzzi, S. J., Fegan, E. C., Ferrara, J., Finke, G., Fitzpatrick, W. B., Focke, A., Franckowiak, Y., Fukazawa, S., Funk, P., Fusco, F., Gargano, N., Gehrel, S., Germani, M., Gibby, N., Giglietto, M., Gile, F., Giordano, M., Giroletti, G., Godfrey, J., Granot, I. A., Grenier, J. E., Grove, D., Gruber, S., Guiriec, D., Hadasch, Y., Hanabata, A. K., Harding, M., Hayashida, E., Hay, D., Horan, R. E., Hughe, Y., Inoue, T., Jogler, G., Johannesson, W. N., Johnson, T., Kawano, J., Knoedlseder, D., Kocevski, M., Ku, J., Lande, S., Larsson, L., Latronico, Longo, Francesco, F., Loparco, M. N., Lovellette, P., Lubrano, M., Mayer, M. N., Mazziotta, J. E., Mcenery, P. F., Michelson, T., Mizuno, A. A., Moiseev, M. E., Monzani, E., Moretti, A., Morselli, I. V., Moskalenko, S., Murgia, R., Nemmen, E., Nu, M., Ohno, T., Ohsugi, A., Okumura, N., Omodei, M., Orienti, D., Paneque, V., Pelassa, J. S., Perkin, M., Pesce Rollin, V., Petrosian, F., Piron, G., Pivato, T. A., Porter, J. L., Racusin, S., Raino, R., Rando, M., Razzano, S., Razzaque, A., Reimer, O., Reimer, S., Ritz, M., Roth, F., Ryde, A., Sartori, P. M., Saz, J. D., Scargle, A., Schulz, C., Sgro, E. J., Siskind, E., Sonba, G., Spandre, P., Spinelli, H., Tajima, H., Takahashi, J. G., Thayer, J. B., Thayer, D. J., Thompson, L., Tibaldo, M., Tinivella, D. F., Torre, G., Tosti, E., Troja, T. L., Usher, J., Vandenbroucke, V., Vasileiou, G., Vianello, V., Vitale, B. L., Winer, K. S., Wood, R., Yamazaki, G., Youne, H. . ., F., S. J., Zhu, P. N., Bhat, M. S., Brigg, D., Byrne, S., Foley, A., Goldstein, P., Jenke, R. M., Kippen, C., Kouveliotou, S., Mcbreen, C., Meegan, W. S., Paciesa, R., Preece, A., Rau, D., Tierney, A. J., Van, A. v., Kienlin, C., Wilson Hodge, S., Xiong, G., Cusumano, V. L., Parola, J. R., Cummings, and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, SPECTRAL COMPONENT, Synchrotron radiation, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, LARGE-AREA TELESCOPE, HIGH-ENERGY EMISSION, AFTERGLOWS, PROMPT, law.invention, Telescope, Spitzer Space Telescope, law, Astrophysics::Galaxy Astrophysics, Physics, Multidisciplinary, Gamma ray, GRB 130427A, Astronomy, Afterglow, GRB, Fermi-LAT, ddc:500, Astrophysics - High Energy Astrophysical Phenomena, Gamma-ray burst, Fermi Gamma-ray Space Telescope
Abstract

The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide constraints on the nature of such unique astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon (95 GeV), longest $\gamma$-ray duration (20 hours), and one of the largest isotropic energy releases ever observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge the widely accepted model that the non-thermal high-energy emission in the afterglow phase of GRBs is synchrotron emission radiated by electrons accelerated at an external shock., Comment: 30 pages, 6 figures. Accepted for publication in Science. Corresponding authors: S. Zhu (sjzhu@umd.edu); J. Chiang (jchiang@slac.stanford.edu); C. Dermer (charles.dermer@nrl.navy.mil); N. Omodei (nicola.omodei@stanford.edu); G. Vianello (giacomov@slac.stanford.edu); S. Xiong (Shaolin.Xiong@uah.edu)

Published
2014
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117. Constraints on the Emission Geometries and Spin Evolution of Gamma-ray Millisecond Pulsars

Author

Xian Hou, Lucas Guillemot, Elizabeth C. Ferrara, Paul S. Ray, Alice K. Harding, Michael Kramer, Tyrel J. Johnson, David A. Smith, J. Lande, P. R. den Hartog, Omer Celik, Christo Venter, University of Southern California (USC), Centre for Space Research [Potchefstroom], North-West University [Potchefstroom] (NWU), GSFC Astrophysics Science Division, NASA Goddard Space Flight Center (GSFC), 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), 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)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), 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 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), Vrije Universiteit Medical Centre (VUMC), Vrije Universiteit Amsterdam [Amsterdam] (VU), University of San Francisco (USF), Twitter Inc., Twitter Inc, Naval Research Laboratory (NRL), and NASAAstrophysicsTheory grants and Fermi Guest Investigator grants 10-Fermi10-C4-0054 and 09-FERMI309-0076

Subjects
[PHYS.ASTR.HE]Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, 01 natural sciences, law.invention, Telescope, Pulsar, law, Millisecond pulsar, 0103 physical sciences, 010306 general physics, 010303 astronomy & astrophysics, acceleration of particles, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Gamma ray, Astronomy and Astrophysics, Light curve, 3. Good health, gamma rays, Space and Planetary Science, Phase space, pulsars, Caustic (optics), Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract

Millisecond pulsars (MSPs) are a growing class of gamma-ray emitters. Pulsed gamma-ray signals have been detected from more than 40 MSPs with the Fermi Large Area Telescope (LAT). The wider radio beams and more compact magnetospheres of MSPs enable studies of emission geometries over a broader range of phase space than non-recycled radio-loud gamma-ray pulsars. We have modeled the gamma-ray light curves of 40 LAT-detected MSPs using geometric emission models assuming a vacuum retarded-dipole magnetic field. We modeled the radio profiles using a single-altitude hollow-cone beam, with a core component when indicated by polarimetry; however, for MSPs with gamma-ray and radio light curve peaks occurring at nearly the same rotational phase we assume that the radio emission is co-located with the gamma rays and caustic in nature. The best-fit parameters and confidence intervals are determined using a maximum likelihood technique. We divide the light curves into three model classes, with gamma-ray peaks trailing (Class I), aligned (Class II) or leading (Class III) the radio peaks. Outer gap and slot gap (two-pole caustic) models best fit roughly equal numbers of Class I and II, while Class III are exclusively fit with pair-starved polar cap models. Distinguishing between the model classes based on typical derived parameters is difficult. We explore the evolution of magnetic inclination angle with period and spin-down power, finding possible correlations. While the presence of significant off-peak emission can often be used as a discriminator between outer gap and slot gap models, a hybrid model may be needed., Comment: Accepted for publication in ApJS, auxiliary files can be found at the entry for this paper at http://www-glast.stanford.edu/cgi-bin/pubpub

Published
2014
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118. Pulsar Polar Cap Heating and Surface Thermal X‐Ray Emission. I. Curvature Radiation Pair Fronts

Author

Alice K. Harding and Alexander G. Muslimov

Subjects
Physics, Photon, Astrophysics::High Energy Astrophysical Phenomena, Electric-field screening, Astrophysics (astro-ph), FOS: Physical sciences, Astronomy and Astrophysics, Electron, Astrophysics, Radiation, Curvature, Magnetic field, Pulsar, Space and Planetary Science, Thermal
Abstract

We investigate the effect of pulsar polar cap (PC) heating produced by positrons returning from the upper pair formation front. Our calculations are based on a self-consistent treatment of the pair dynamics and the effect of electric field screening by the returning positrons. We calculate the resultant X-ray luminosities, and discuss the dependence of the PC heating efficiencies on pulsar parameters, such as characteristic spin-down age, spin period, and surface magnetic field strength. In this study we concentrate on the regime where the pairs are produced in a magnetic field by curvature photons emitted by accelerating electrons. Our theoretical results are not in conflict with the available observational X-ray data and suggest that the effect of PC heating should significantly contribute to the thermal X-ray fluxes from middle-aged and old pulsars. The implications for current and future X-ray observations of pulsars are briefly outlined., 28 pages, 7 figures, accepted for publication in ApJ

Published
2001
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119. Full Polar Cap Cascade Scenario: Gamma‐Ray and X‐Ray Luminosities from Spin‐powered Pulsars

Author

Alice K. Harding and Bing Zhang

Subjects
Physics, Photon, Astrophysics::High Energy Astrophysical Phenomena, Gamma ray, Astronomy and Astrophysics, Astrophysics, Neutron star, Pulsar, Space and Planetary Science, Millisecond pulsar, ROSAT, Multipole expansion, Energy (signal processing)
Abstract

We modify polar cap cascade picture to include the ICS of the higher generation pairs. In such a ``full-cascade'' scenario, not only the perpendicular portion of the energy of the pairs goes to high energy radiation via SR, but the parallel portion of the energy of the pairs can also contribute to high energy emission via ICS with the soft thermal photons from either the full neutron star surface or the hot polar cap. An important output of such a scenario is that the soft tail of the ICS spectrum can naturally result in a non-thermal X-ray component which can contribute to the luminosities observed by ROSAT and ASCA. Here we present an analytic description of such a full polar cap cascade scenario within the framework of Harding & Muslimov acceleration model. We present the theoretical predictions of the $\gamma$-ray luminosities, the thermal and non-thermal X-ray luminosities for the known spin-powered X-ray pulsars. Our results show that the observed different dependences of the high energy luminosities on the pulsar spin-down luminosities, i.e., $L_\gamma \propto (L_{\rm sd})^{1/2}$ and $L_x \sim 10^{-3} L_{\rm sd}$, are well reproduced. Our model predicts that the {\em pulsed} soft X-rays in the ROSAT band from most of the millisecond pulsars might be of thermal origin if there is no strong multipole field components near the surfaces of these pulsars., Comment: 23 pages, emulateapj style, final version to appear in the Astrophysical Journal

Published
2000
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120. ARossi X‐Ray Timing ExplorerObservation of the Vela Pulsar: Filling in the X‐Ray Gap

Author

M. S. Strickman, Alice K. Harding, and O. C. deJager

Subjects
Physics, biology, Astrophysics::High Energy Astrophysical Phenomena, Phase (waves), Astronomy and Astrophysics, Astrophysics, biology.organism_classification, Vela, Pulse (physics), Orders of magnitude (time), Pulsar, Space and Planetary Science, ROSAT, Egret, Electronic band structure
Abstract

We have detected pulsed emission from the Vela pulsar at 2 - 30 keV during a 93 ks observation with the Rossi X-Ray Timing Explorer (RXTE). The RXTE pulse profile shows two peaks, that are roughly in phase with the EGRET peaks, but does not show any significant interpeak emission. The phase of Peak 2 is energy dependent, moving to higher phase with increasing energy in the RXTE band, in phase alignment with the second optical pulse in the lowest energy band of 2 - 8 keV and in phase alignment with the second EGRET pulse in the highest energy band of 16-30 keV. The average pulse spectrum joins smoothly to the high energy spectrum of OSSE, COMPTEL and EGRET, although the spectrum of Peak 1 is significantly harder than that of Peak 2. A break or turnover in the spectrum around 50 keV, previously suggested by OSSE data, is now clearly defined. The RXTE spectrum falls several orders of magnitude below the ROSAT emission in the 0.1 - 2 keV band, suggesting a thermal origin for the ROSAT pulse.

Published
1999
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121. Cyclotron Line Features from Near‐critical Magnetic Fields: The Effect of Optical Depth and Plasma Geometry

Author

Rafael A. Araya and Alice K. Harding

Subjects
Physics, Photon, Space and Planetary Science, Scattering, Monte Carlo method, Compton scattering, Astronomy and Astrophysics, Geometry, Emission spectrum, Atomic physics, Spectral line, Line (formation), Magnetic field
Abstract

A detailed analytical study of the relativistic profile for magnetic Compton scattering is performed and use is made of Monte Carlo methods to construct a numerical scheme for the production of relativistic theoretical cyclotron spectra from internally irradiated scattering atmospheres in the low-density/high-field regime. The cross section includes natural line widths, and the Monte Carlo implementation allows for spatial diffusion of photons in arbitrary geometries while accounting for relativistic angular redistribution. Detailed consideration of "Raman-Landau" scattering permits photon spawning from up to fourth harmonic photons. This scheme is utilized to make specific predictions on the effect of geometry and optical depth on the formation of cyclotron lines in hard incident continua. Even if the injection is isotropic, a strongly anisotropic radiation field ensues at relatively low optical depths. The scattering profiles at large angles and low fields are highly asymmetric and peak at the relativistic energy cutoff, not necessarily at the resonant energy. Higher harmonic features in general bear little resemblance to the fundamental even at high fields (B~10 TG), and slabs yield the deepest features, while cylinders present the widest lines at small angles. Moreover, the fundamental line photons in slab scattering regions tend to redistribute to the line wings from all angles, producing fairly broad emission line wings at small angles. Higher optical depths at those angles hampers such redistribution in cylindrical geometries.

Published
1999
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122. Rossi X‐Ray Timing ExplorerObservation of PSR B1706−44 and Implications for Theoretical Models of Pulsar Emission

Author

M. S. Strickman, Alak Ray, and Alice K. Harding

Subjects
Physics, Particle acceleration, Photon, Pulsar, Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, ROSAT, Theoretical models, Flux, Astronomy and Astrophysics, Context (language use), Astrophysics
Abstract

We report on results of an observation with the Rossi X-Ray Timing Explorer (RXTE) of PSR B1706-44 with a live time of 132 ks, to search for pulsed X-ray emission. PSR B1706-44 is a radio and high-energy gamma-ray pulsar (detected by EGRET), but no pulsed emission has been detected in the X-ray band. Since most of the other known gamma-ray pulsars emit pulsed X-rays, it is expected that PSR B1706-44 would also be an X-ray pulsar. However, while the ROSAT PSPC detected a source at the pulsar position, it did not detect pulsations, giving a pulsed fraction upper limit of 18%. The RXTE observations to search for modulation at the pulsar period were carried out in November 1996 and May 1997, during the low states of the nearby X-ray binary 4U1705-44. No significant modulation was detected at the pulsar period, giving an upper limit of 10^{-6} photons cm^{-2} s^{-1} keV^{-1} in the interval 9 keV < E < 18.5keV. The implications of this upper limit of the pulsed flux from the RXTE observation, taken together with multiband observations of this pulsar are examined in the context of theoretical models of pulsar particle acceleration zones.

Published
1999
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123. Radio-Quiet Pulsars with Ultrastrong Magnetic Fields

Author

Alice K. Harding and Matthew G. Baring

Subjects
Physics, education.field_of_study, Photon, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), Population, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Magnetic field, Neutron star, Dipole, Pair production, Pulsar, Space and Planetary Science, education, Magnetic dipole
Abstract

The notable absence of radio pulsars having measured magnetic dipole surface field strengths above $B_0\sim 3\times 10^{13}$ Gauss naturally raises the question of whether this forms an upper limit to pulsar magnetization. Recently there has been increasing evidence that neutron stars possessing higher dipole spin-down fields do in fact exist, including a growing list of anomalous X-ray pulsars (AXPs) with long periods and spinning down with high period derivatives, implying surface fields of $10^{14}$--$10^{15}$ Gauss. Furthermore, the recently reported X-ray period and period derivative for the Soft Gamma-ray Repeater (SGR) source SGR1806-20 suggest a surface field around $10^{15}$ Gauss. None of these high-field pulsars have yet been detected as radio pulsars. We propose that high-field pulsars should be radio-quiet because electron-positron pair production in their magnetospheres, thought to be essential for radio emission, is efficiently suppressed in ultra-strong fields ($B_0\gtrsim 4\times 10^{13}$ Gauss) by the action of photon splitting, a quantum electrodynamical process in which a photon splits into two. Our computed radio quiescence boundary in the radio pulsar $P-\dot P$ diagram, where photon splitting overtakes pair creation, is located just above the boundary of the known radio pulsar population, neatly dividing them from the AXPs. We thus identify a physical mechanism that defines a new class of high-field radio-quiet neutron stars that should be detectable by their pulsed emission at X-ray and perhaps $\gamma$-ray energies., Comment: 4 pages, including one figure and one table, in AASTeX emulatapj format, Astrophysical Journal Letters, in press

Published
1998
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124. Pulsar X‐Ray and Gamma‐Ray Pulse Profiles: Constraint on Obliquity and Observer Angles

Author

Alice K. Harding and Alexander G. Muslimov

Subjects
Physics, Photon, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), Phase (waves), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Magnetic field, Pulse (physics), Pulsar, Space and Planetary Science, Phase space, Anisotropy, Beam (structure)
Abstract

We model the thermal X-ray profiles of Geminga, Vela and PSR 0656+14, which have also been detected as gamma-ray pulsars, to constrain the phase space of obliquity and observer angles required to reproduce the observed X-ray pulsed fractions and pulse widths. These geometrical constraints derived from the X-ray light curves are explored for various assumptions about surface temperature distribution and flux anisotropy caused by the magnetized atmosphere. We include curved spacetime effects on photon trajectories and magnetic field. The observed gamma-ray pulse profiles are double peaked with phase separations of 0.4 - 0.5 between the peaks. Assuming that the gamma-ray profiles are due to emission in a hollow cone centered on the magnetic pole, we derive the constraints on the phase space of obliquity and observer angles, for different gamma-ray beam sizes, required to produce the observed gamma-ray peak phase separations. We compare the constraints from the X-ray emission to those derived from the observed gamma-ray pulse profiles, and find that the overlapping phase space requires both obliquity and observer angles to be smaller than 20-30 degrees, implying gamma-ray beam opening angles of at most 30-35 degrees., 29 pages, 9 embedded figures, AASTEX v.4, To appear in ApJ, June 20, 1998 (Vol. 499)

Published
1998
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125. Pair production opacities for gamma-ray burst spectra in the 10 GeV–1 TeV range

Author

Matthew G. Baring and Alice K. Harding

Subjects
Physics, Atmospheric Science, biology, Opacity, Astrophysics::High Energy Astrophysical Phenomena, Aerospace Engineering, Astronomy, Astronomy and Astrophysics, Astrophysics, biology.organism_classification, Spectral line, Galactic halo, Lorentz factor, symbols.namesake, Geophysics, Pair production, Space and Planetary Science, Milagro, symbols, General Earth and Planetary Sciences, Egret, Gamma-ray burst
Abstract

Recent calculations of pair production opacities for gamma-ray bursts detected by EGRET have suggested that relativistic bulk motion with large Lorentz factors must exist in these sources, whether of galactic or cosmological origin, to permit the emergence of a high energy continuum. The extant calculations usually assume an infinite power-law source spectrum for simplicity, an approximation that is quite adequate for most bursts detected by EGRET. However, for a given bulk Lorentz factor, photons above the EGRET range can potentially interact with sub-MeV photons in pair production opacity calculations, so it is important to accurately include the spectral curvature in bursts seen by BATSE. In this paper we modify our previous work to include such spectral forms, well-represented by broken power-laws, determining opacity as a function of energy for different source Lorentz factors Γ. The comparative depletion of low energy photons below 1 MeV turns out to be immaterial to considerations of bulk motion in cosmological bursts, but is crucial to estimates of source transparency in the 1 GeV – 1 TeV range for sources located in the galactic halo. We find that broad absorption dips can arise at these energies for suitable expansion parameters. Whipple, MILAGRO and GLAST will play an important role in the observation of the presence or absence of such distinctive structure in GRB spectra.

Published
1998
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126. Numerical evaluation of magnetic photon splitting rates via a proper-time technique

Author

Matthew G. Baring and Alice K. Harding

Subjects
Physics, Atmospheric Science, Magnetic photon, Photon, Astrophysics::High Energy Astrophysical Phenomena, Computation, Multiple integral, Aerospace Engineering, Astronomy and Astrophysics, Polarization (waves), Magnetar, Computational physics, Geophysics, Pulsar, Space and Planetary Science, Quantum mechanics, General Earth and Planetary Sciences, Proper time
Abstract

The results of our numerical computation of magnetic photon splitting rates according to the proper-time formulation developed by Stoneham are presented in this paper. Calculations were performed for both the total rate of splitting and the differential distributions for the polarization mode ⊥ → ∥∥ of splitting. Analytic asymptotic limits obtainable from the triple integral expressions of Stoneham's formalism are also presented, and these are reproduced by the full computation of the integrals. The rates produced here agree with numerous previous analyses of photon splitting but fall somewhat below the S-matrix calculation of Wilke and Wunner. The numerical determination of these rates is of great use to current topical models of gamma-ray pulsars and magnetar scenarios for soft gamma repeaters.

Published
1998
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127. Toward the Quasi–Steady State Electrodynamics of a Neutron Star

Author

Alexander G. Muslimov and Alice K. Harding

Subjects
Physics, Neutron star, Theory of relativity, Space and Planetary Science, General relativity, Electric field, Quantum electrodynamics, Charge density, Magnetosphere, Astronomy and Astrophysics, Electron, Charged particle
Abstract

We consider the electrodynamics of a rotating magnetized neutron star with allowance for the quasi-steady state regime of charged particle ejection from the polar cap into the inner magnetosphere. We derive basic equations within the framework of a general relativistic formalism and present the analytic solutions. We demonstrate that the quasi-steady state supply of electrons into the region of open field lines reduces the total power put into the acceleration of primary particles, although the total power corresponding to a steady state solution in general relativity is increased compared to the flat-space solution. Also, we illustrate that temporarily modulated ejection of electrons from the stellar surface results in substantial modulation of an accelerating electric field and charge density along the open field lines. We briefly outline the implications of this effect for the pulsars.

Published
1997
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128. Pair Production Absorption Troughs in Gamma-Ray Burst Spectra: A Potential Distance Discriminator

Author

Alice K. Harding and Matthew G. Baring

Subjects
Physics, education.field_of_study, Opacity, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), Population, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Spectral line, Galactic halo, Lorentz factor, symbols.namesake, Pair production, Space and Planetary Science, Milagro, symbols, Gamma-ray burst, education
Abstract

Relativistic bulk motion with large Lorentz factors has recently been inferred for gamma-ray bursts regardless of whether they are of galactic or cosmological origin. This conclusion results from calculations of internal pair production transparency in bursts that usually assume an infinite power-law source spectrum for simplicity, an approximation that is quite adequate for some bursts detected by EGRET. However, for a given bulk Lorentz factor \teq{\Gamma}, photons above the EGRET range can potentially interact with sub-MeV photons in such calculations. Hence it is essential to accurately address the spectral curvature in bursts seen by BATSE. In this paper we present the major properties induced in photon-photon opacity considerations by such spectral curvature. The observed spectral breaks around 1 MeV turn out to be irrelevant to opacity in cosmological bursts, but are crucial to estimates of source transparency in the 1 GeV -- 1 TeV range for sources located in the galactic halo. We find that broad absorption troughs can arise at these energies for suitable bulk motion parameters \teq{\Gamma}. Such troughs are probably an unambiguous signature of a galactic halo population, and if observed by experiments such as Whipple, MILAGRO and GLAST, would provide powerful evidence that such bursts are not at cosmological distances., Comment: 10 pages, AASTeX format, including 2 eps figures, ApJLett in press

Published
1997
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129. The Vela-X Pulsar Wind Nebula Revisited with Four Years of Fermi Large Area Telescope Observations

Author

Roger W. Romani, Alice K. Harding, L. Guillemot, M. Lemoine-Goumard, M.-H. Grondin, and T. Reposeur

Subjects
Physics, Nebula, 010504 meteorology & atmospheric sciences, Vela Supernova Remnant, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Vela, 01 natural sciences, Pulsar wind nebula, law.invention, Telescope, Pulsar, Space and Planetary Science, law, 0103 physical sciences, Supernova remnant, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Fermi Gamma-ray Space Telescope
Abstract

The Vela supernova remnant is the closest supernova remnant to Earth containing an active pulsar, the Vela pulsar (PSR B0833-45). This pulsar is the archetype of the middle-aged pulsar class and powers a bright pulsar wind nebula (PWN), Vela-X, spanning a region of 2{\deg} x 3{\deg} south of the pulsar and observed in the radio, X-ray and very high energy gamma-ray domains. The detection of the Vela-X PWN by the Fermi Large Area Telescope (LAT) was reported in the first year of the mission. Subsequently, we have re-investigated this complex region and performed a detailed morphological and spectral analysis of this source using 4 years of Fermi-LAT observations. This study lowers the threshold for morphological analysis of the nebula from 0.8 GeV to 0.3 GeV, allowing inspection of distinct energy bands by the LAT for the first time. We describe the recent results obtained on this PWN and discuss the origin of the newly detected spatial features.

Published
2013
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130. Fermi LAT pulsed detection of PSR J0737-3039A in the double pulsar system

Author

H. A. Craig, Tyrel J. Johnson, Christo Venter, Michael Kramer, Matthew Kerr, Lucas Guillemot, Alice K. Harding, Robert D. Ferdman, Roger W. Romani, Ingrid H. Stairs, and 12006653 - Venter, Christo

Subjects
individual (PSR J0737-3039A, PSR J0737-3039B) [Pulsars], Astrophysics::High Energy Astrophysical Phenomena, general [Pulsars], Magnetosphere, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, law.invention, Telescope, Pulsar, law, Millisecond pulsar, 0103 physical sciences, 010306 general physics, 010303 astronomy & astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Gamma ray, stars [Gamma rays], Astronomy and Astrophysics, Light curve, Astrophysics - Astrophysics of Galaxies, Supernova, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract

We report the Fermi Large Area Telescope discovery of gamma-ray pulsations from the 22.7 ms pulsar A in the double pulsar system J0737-3039A/B. This is the first mildly recycled millisecond pulsar (MSP) detected in the GeV domain. The 2.7 s companion object PSR J0737-3039B is not detected in gamma rays. PSR J0737-3039A is a faint gamma-ray emitter, so that its spectral properties are only weakly constrained; however, its measured efficiency is typical of other MSPs. The two peaks of the gamma-ray light curve are separated by roughly half a rotation and are well offset from the radio and X-ray emission, suggesting that the GeV radiation originates in a distinct part of the magnetosphere from the other types of emission. From the modeling of the radio and the gamma-ray emission profiles and the analysis of radio polarization data, we constrain the magnetic inclination $\alpha$ and the viewing angle $\zeta$ to be close to 90$^\circ$, which is consistent with independent studies of the radio emission from PSR J0737-3039A. A small misalignment angle between the pulsar's spin axis and the system's orbital axis is therefore favored, supporting the hypothesis that pulsar B was formed in a nearly symmetric supernova explosion as has been discussed in the literature already., Comment: Published in the Astrophysical Journal (ApJ 768, 169, 2013). Updated to reflect changes made at the proof stage

Published
2013

131. Modeling the non-recycled Fermi gamma-ray pulsar population

Author

Benetge Perera, T. H. Burnett, J. M. Cordes, Alice K. Harding, Matthew Kerr, and Maura McLaughlin

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), education.field_of_study, Line-of-sight, Astrophysics::High Energy Astrophysical Phenomena, Population, Gamma ray, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Luminosity, Stars, Pulsar, Spitzer Space Telescope, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, education, Astrophysics - High Energy Astrophysical Phenomena, Solar and Stellar Astrophysics (astro-ph.SR), Fermi Gamma-ray Space Telescope
Abstract

We use Fermi Gamma-ray Space Telescope detections and upper limits on non-recycled pulsars obtained from the Large Area Telescope (LAT) to constrain how the gamma-ray luminosity L depends on the period P and the period derivative \dot{P}. We use a Bayesian analysis to calculate a best-fit luminosity law, or dependence of L on P and \dot{P}, including different methods for modeling the beaming factor. An outer gap (OG) magnetosphere geometry provides the best-fit model, which is L \propto P^{-a} \dot{P}^{b} where a=1.36\pm0.03 and b=0.44\pm0.02, similar to but not identical to the commonly assumed L \propto \sqrt{\dot{E}} \propto P^{-1.5} \dot{P}^{0.5}. Given upper limits on gamma-ray fluxes of currently known radio pulsars and using the OG model, we find that about 92% of the radio-detected pulsars have gamma-ray beams that intersect our line of sight. By modeling the misalignment of radio and gamma-ray beams of these pulsars, we find an average gamma-ray beaming solid angle of about 3.7{\pi} for the OG model, assuming a uniform beam. Using LAT-measured diffuse fluxes, we place a 2{\sigma} upper limit on the average braking index and a 2{\sigma} lower limit on the average surface magnetic field strength of the pulsar population of 3.8 and 3.2 X 10^{10} G, respectively. We then predict the number of non-recycled pulsars detectable by the LAT based on our population model. Using the two-year sensitivity, we find that the LAT is capable of detecting emission from about 380 non-recycled pulsars, including 150 currently identified radio pulsars. Using the expected five-year sensitivity, about 620 non-recycled pulsars are detectable, including about 220 currently identified radio pulsars. We note that these predictions significantly depend on our model assumptions., Comment: 26 pages, 10 figures, Accepted by ApJ on 8 September 2013

Published
2013
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132. ERRATUM: 'FERMI LARGE AREA TELESCOPE STUDY OF COSMIC-RAYS AND THE INTERSTELLAR MEDIUM IN NEARBY MOLECULAR CLOUDS' (2012, ApJ, 755, 22)

Author

P. Lubrano, Denis Bastieri, Hartmut Sadrozinski, Sho Nishino, J. Lande, Sylvain Guiriec, Charles D. Dermer, F. Gargano, Rodrigo Nemmen, A. Chekhtman, D. Horan, Tadayuki Takahashi, M. Tinivella, M. Roth, Francesco Longo, Elizabeth C. Ferrara, W. B. Focke, P. Spinelli, Pierrick Martin, Francesco Giordano, Igor V. Moskalenko, I. A. Grenier, Olaf Reimer, A. Tramacere, E. J. Siskind, Takaaki Tanaka, C. Favuzzi, Stephan Zimmer, J. H. Panetta, Alice Allafort, Gloria Spandre, Markus Ackermann, R. A. Cameron, T. J. Brandt, P. Bruel, S. Murgia, Johann Cohen-Tanugi, T. L. Usher, Hiromitsu Takahashi, F. Piron, T. A. Porter, G. Busetto, Brian L Winer, G. A. Caliandro, J. M. Casandjian, Yasunobu Uchiyama, M. Razzano, Y. Hanabata, Masanori Ohno, A. Morselli, V. Vasileiou, V. Vitale, Stefan Funk, M. E. Monzani, E. Orlando, Zhenwei Yang, G. Pivato, A. A. Moiseev, R. Claus, J. Bregeon, Carmelo Sgrò, Riccardo Rando, E. Nuss, David Paneque, X. Hou, M. Kuss, T. Kamae, T. Ohsugi, Eleonora Troja, Miranda Jackson, Alice K. Harding, A. W. Borgland, A. De Angelis, T. Uehara, L. Falletti, G. Tosti, Eugenio Bottacini, Daniel Sánchez, S. J. Fegan, B. Berenji, M. H. Grondin, Gudlaugur Johannesson, Seth Digel, F. Loparco, Giacomo Vianello, O. Tibolla, W. Mitthumsiri, M. Naumann-Godo, Claudia Cecchi, Jürgen Knödlseder, Justin Vandenbroucke, R. E. Hughes, Eric Charles, Andrew W. Strong, Guido Barbiellini, Alex Drlica-Wagner, K. Hayashi, D. J. Suson, Nicola Giglietto, Keith Bechtol, Shiu-Hang Lee, Marianne Lemoine-Goumard, Dario Gasparrini, A. P. Waite, M. Ozaki, C. Monte, Ronaldo Bellazzini, T. Glanzman, M. N. Lovellette, P. A. Caraveo, Persis S. Drell, P. Wang, Nicola Omodei, D. J. Thompson, M. Brigida, Emanuele Bonamente, T. Sada, Jun Kataoka, S. Germani, K. S. Wood, A. S. Johnson, S. Larsson, Jay P. Norris, James Chiang, Roger Blandford, S. Rainò, Tsunefumi Mizuno, J. E. Grove, Yasushi Fukazawa, P. Fusco, Hiroaki Yamamoto, A. Reimer, J. F. Ormes, J. G. Thayer, J. Mehault, Carla Sbarra, Julie McEnery, Marco Ajello, J. B. Thayer, L. Tibaldo, S. Buson, D. Parent, Yasuo Fukui, Melissa Pesce-Rollins, Luca Baldini, M. Pierbattista, Diego F. Torres, Mn Mazziotta, C. Romoli, E. Do Couto E Silva, Jean Ballet, Stefano Ciprini, Elliott D. Bloom, R. Buehler, Peter F. Michelson, Marcello Giroletti, Hideaki Katagiri, F. D'Ammando, Akira Okumura, Daniela Hadasch, Jan Conrad, G. Godfrey, F. de Palma, and Ryosuke Itoh

Subjects
Physics, Molecular cloud, Astronomy, Astronomy and Astrophysics, Cosmic ray, Astrophysics, law.invention, Interstellar medium, Telescope, Space and Planetary Science, law, ddc:520, Fermi Gamma-ray Space Telescope
Abstract

The astrophysical journal 778(1), 82 (2013). doi:10.1088/0004-637X/778/1/82, This is an Erratum for the article 2012 ApJ 755 22, Published by Univ.11032, Chicago, Ill. [u.a.]

Published
2013
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133. PSR J2021+4026 IN THE GAMMA CYGNI REGION: THE FIRST VARIABLE γ-RAY PULSAR SEEN BY THE Fermi LAT

Author

S. Murgia, I. A. Grenier, F. Piron, Alice K. Harding, Seth Digel, T. Jogler, Rodrigo Nemmen, P. Fusco, D. Horan, Matthew Kerr, A. B. Hill, David A. Smith, Hiromitsu Takahashi, Francesco Longo, E. Orlando, Olaf Reimer, Dario Gasparrini, J. B. Thayer, T. A. Porter, Nicola Omodei, C. Favuzzi, R. C. G. Chaves, Y. Uchiyama, R. Buehler, Brian L Winer, Paul S. Ray, E. Hays, Alice Allafort, S. Buson, A. Chekhtman, P. Lubrano, Marcello Giroletti, S. Rainò, D. J. Thompson, Tsunefumi Mizuno, F. Loparco, G. Chiaro, R. Claus, M. Pierbattista, J. Méhault, E. J. Siskind, K. Hayashi, P. Spinelli, T. Ohsugi, John W. Hewitt, P. Bruel, V. Vasileiou, T. J. Brandt, Claudia Cecchi, T. J. Johnson, Carmelo Sgrò, Riccardo Rando, Luca Baldini, Christo Venter, Diego F. Torres, E. Nuss, David Paneque, R. A. Cameron, Sylvain Guiriec, M. Kuss, Mn Mazziotta, X. Hou, F. Gargano, A. Franckowiak, K. S. Wood, Luca Latronico, G. Tosti, Johan Bregeon, M. Tinivella, Elizabeth C. Ferrara, Giacomo Vianello, Jürgen Knödlseder, Emanuele Bonamente, G. Godfrey, Melissa Pesce-Rollins, T. Reposeur, M. Razzano, F. de Palma, Filippo D'Ammando, A. Morselli, V. Vitale, Ronaldo Bellazzini, Marianne Lemoine-Goumard, M. E. Monzani, Matthew G. Baring, Daniela Hadasch, A. S. Johnson, James Chiang, M. Marelli, M. Hayashida, L. Di Venere, G. A. Caliandro, T. L. Usher, Roger W. Romani, Jean Ballet, Stefano Ciprini, M. Mayer, Nicola Giglietto, P. A. Caraveo, Persis S. Drell, Justin Vandenbroucke, Guido Barbiellini, S. Larsson, M. Orienti, D. Malyshev, L. Tibaldo, Denis Bastieri, J. Lande, P. M. Saz Parkinson, Andrew W. Strong, Alberto Sartori, T. Glanzman, G. Pivato, Eugenio Bottacini, 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), 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), 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), Istituto Nazionale di Fisica Nucleare, sezione di Bari (INFN, sezione di Bari), National Institute for Nuclear Physics (INFN), IEEC-CSIC, Universitat Autònoma de Barcelona [Barcelona] (UAB), 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), FERMI, 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)-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), 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 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), Istituto Nazionale di Fisica Nucleare (INFN), Universitat Autònoma de Barcelona (UAB), 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), 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 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)-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), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), 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), 12006653 - Venter, Christo, Allafort, A., Baldini, L., Ballet, J., BARBIELLINI AMIDEI, Guido, Baring, M. G., Bastieri, D., Bellazzini, R., Bonamente, E., Bottacini, E., Brandt, T. J., Bregeon, J., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Caraveo, P. A., Cecchi, C., Chaves, R. C. G., Chekhtman, A., Chiang, J., Chiaro, G., Ciprini, S., Claus, R., D'Ammando, F., de Palma, F., Digel, S. W., Di Venere, L., Drell, P. S., Favuzzi, C., Ferrara, E. C., Franckowiak, A., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giroletti, M., Glanzman, T., Godfrey, G., Grenier, I. A., Guiriec, S., Hadasch, D., Harding, A. K., Hayashida, M., Hayashi, K., Hays, E., Hewitt, J., Hill, A. B., Horan, D., Hou, X., Jogler, T., Johnson, A. S., Johnson, T. J., Kerr, M., Knödlseder, J., Kuss, M., Lande, J., Larsson, S., Latronico, L., Lemoine Goumard, M., Longo, Francesco, Loparco, F., Lubrano, P., Malyshev, D., Marelli, M., Mayer, M., Mazziotta, M. N., Mehault, J., Mizuno, T., Monzani, M. E., Morselli, A., Murgia, S., Nemmen, R., Nuss, E., Ohsugi, T., Omodei, N., Orienti, M., Orlando, E., Paneque, D., Pesce Rollins, M., Pierbattista, M., Piron, F., Pivato, G., Porter, T. A., Rainò, S., Rando, R., Ray, P. S., Razzano, M., Reimer, O., Reposeur, T., Romani, R. W., Sartori, A., Saz Parkinson, P. M., Sgrò, C., Siskind, E. J., Smith, D. A., Spinelli, P., Strong, A. W., Takahashi, H., Thayer, J. B., Thompson, D. J., Tibaldo, L., Tinivella, M., Torres, D. F., Tosti, G., Uchiyama, Y., Usher, T. L., Vandenbroucke, J., Vasileiou, V., Venter, C., Vianello, G., Vitale, V., Winer, B. L., Wood, K. S., Allafort A, Baldini L, Ballet J, Barbiellini G, Baring MG, Bastieri D, Bellazzini R, Bonamente E, Bottacini E, Brandt TJ, Bregeon J, Bruel P, Buehler R, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Cecchi C, Chaves RCG, Chekhtman A, Chiang J, Chiaro G, Ciprini S, Claus R, DAmmando F, de Palma F, Digel SW, Di Venere L, Drell PS, Favuzzi C, Ferrara EC, Franckowiak A, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Guiriec S, Hadasch D, Harding AK, Hayashida M, Hayashi K, Hays E, Hewitt J, Hill AB, Horan D, Hou X, Jogler T, Johnson AS, Johnson TJ, Kerr M, Knodlseder J, Kuss M, Lande J, Larsson S, Latronico L, Lemoine-Goumard M, Longo F, Loparco F, Lubrano P, Malyshev D, Marelli M, Mayer M, Mazziotta MN, Mehault J, Mizuno T, Monzani ME, Morselli A, Murgia S, Nemmen R, Nuss E, Ohsugi T, Omodei N, Orienti M, Orlando E, Paneque D, Pesce-Rollins M, Pierbattista M, Piron F, Pivato G, Porter TA, Raino S, Rando R, Ray PS, Razzano M, Reimer O, Reposeur T, Romani RW, Sartori A, Parkinson PMS, Sgro C, Siskind EJ, Smith DA, Spinelli P, Strong AW, Takahashi H, Thayer JB, Thompson DJ, Tibaldo L, Tinivella M, Torres DF, Tosti G, Uchiyama Y, Usher TL, Vandenbroucke J, Vasileiou V, Venter C, Vianello G, Vitale V, Winer BL, and Wood KS

Subjects
[PHYS.ASTR.HE]Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Flux, individual: PSR J2021+4026 [pulsars], Astrophysics, gamma rays: stars, 01 natural sciences, star [gamma rays], pulsars: individual (PSR J2021+4026), stars: neutron, Pulsar, gamma rays: star, 0103 physical sciences, Emission spectrum, 010303 astronomy & astrophysics, Physics, pulsars: individual: PSR J2021+4026, 010308 nuclear & particles physics, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Gamma ray, stars [Gamma rays], Astronomy, individual (PSR J2021+4026) [Pulsars], Astronomy and Astrophysics, neutron [Stars], Gamma-ray astronomy, Wavelength, Stars, Space and Planetary Science, ddc:520, Astrophysics - High Energy Astrophysical Phenomena, Gamma rays: stars, Fermi Gamma-ray Space Telescope
Abstract

The astrophysical journal / 2 777(1), L2 (2013). doi:10.1088/2041-8205/777/1/L2, Long-term monitoring of PSR J2021+4026 in the heart of the Cygnus region with the Fermi Large Area Telescope unveiled a sudden decrease in flux above 100 MeV over a timescale shorter than a week. The "jump" was near MJD 55850 (2011 October 16), with the flux decreasing from (8.33 ± 0.08) × 10–10 erg cm–2 s–1 to (6.86 ± 0.13) × 10–10 erg cm–2 s–1. Simultaneously, the frequency spindown rate increased from (7.8 ± 0.1) × 10–13 Hz s–1 to (8.1 ± 0.1) × 10–13 Hz s–1. Significant (>5σ) changes in the pulse profile and marginal (, Published by Institute of Physics Publ., London

Published
2013
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134. Constraints on the Galactic Population of TeV Pulsar Wind Nebulae Using Fermi Large Area Telescope Observations

Author

Janet Conrad, A. Reimer, Xian Hou, M. Tinivella, A. S. Johnson, Elizabeth C. Ferrara, A. Morselli, R. Claus, Marianne Lemoine-Goumard, M. Brigida, Hiromitsu Takahashi, Frederic Piron, V. Vasileiou, Emanuele Bonamente, Kent S. Wood, S. Murgia, C. Cecchi, Dario Gasparrini, M. Orienti, T. Reposeur, Y. Takeuchi, Denis Bastieri, E. Do Couto E Silva, F. Giordano, T. A. Porter, J.H. Panetta, Alice K. Harding, Alex Drlica-Wagner, Melissa Pesce-Rollins, T. J. Brandt, R. C. G. Chaves, W. B. Focke, T. Jogler, John W. Hewitt, L. Falletti, Sylvain Guiriec, A. Chekhtman, E. D. Bloom, Akira Okumura, M. E. Monzani, J. S. Perkins, Nicola Giglietto, Jean Ballet, Markus Ackermann, Tsunefumi Mizuno, V. Vitale, Michael Mayer, Gudlaugur Johannesson, S. J. Fegan, M. N. Lovellette, Stefano Ciprini, J. B. Thayer, E. J. Siskind, Yoshiyuki Inoue, G. Chiaro, P. A. Caraveo, Persis S. Drell, Gino Tosti, Justin Vandenbroucke, R. E. Hughes, Guido Barbiellini, Takeshi Nakamori, T. Grégoire, Luca Baldini, G. Godfrey, Martino Marelli, F. Gargano, T. Ohsugi, J. E. Grove, Yasushi Fukazawa, Francesco Longo, T. Glanzman, Gloria Spandre, M.-H. Grondin, D. J. Thompson, Eleonora Troja, Miranda Jackson, Alice Allafort, M. N. Mazziotta, J. Chiang, F. de Palma, Morihiro Hayashida, J. G. Thayer, Yasunobu Uchiyama, M. Kuss, P. Fusco, Matthew Kerr, L. Di Venere, Giacomo Vianello, Jürgen Knödlseder, Y. Hanabata, Johann Cohen-Tanugi, G. Pivato, T. Kawano, R. Rousseau, C. Favuzzi, G. A. Caliandro, Eugenio Bottacini, Z. Yang, Eric Nuss, J. Lande, Charles D. Dermer, A. Franckowiak, A. B. Hill, Stefan Funk, Michael Werner, Eric Charles, E. Hays, Steven Ritz, D. J. Suson, Carmelo Sgrò, Riccardo Rando, Ronaldo Bellazzini, David Paneque, S. Rainò, Francesco Massaro, J. F. Ormes, S. Cutini, F. Loparco, W. Mitthumsiri, I. A. Grenier, David A. Smith, S. Buson, Fabio Acero, P. Lubrano, C. Monte, R. A. Cameron, Roger Blandford, L. Latronico, Rodrigo Nemmen, Kazuhiko Hayashi, Diego F. Torres, Elena Orlando, D. Horan, J. Mehault, Johan Bregeon, B. L. Winer, Julie McEnery, M. Roth, Marco Ajello, L. Tibaldo, D. Hadasch, Igor V. Moskalenko, Olaf Reimer, Pascal Bruel, Omar Tibolla, R. Buehler, A. Schulz, Peter F. Michelson, Marcello Giroletti, P. Spinelli, Keith Bechtol, Stefan Larsson, M. Razzano, P. M. Saz Parkinson, Filippo D'Ammando, T. Kamae, M. Dalton, 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), 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), 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), 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), Istituto Nazionale di Fisica Nucleare, sezione di Bari (INFN, sezione di Bari), Istituto Nazionale di Fisica Nucleare (INFN), FERMI, 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)-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), Acero F, Ackermann M, Ajello M, Allafort A, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bechtol K, Bellazzini R, Blandford RD, Bloom ED, Bonamente E, Bottacini E, Brandt TJ, Bregeon J, Brigida M, Bruel P, Buehler R, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Cecchi C, Charles E, Chaves RCG, Chekhtman A, Chiang J, Chiaro G, Ciprini S, Claus R, Cohen-Tanugi J, Conrad J, Cutini S, Dalton M, DAmmando F, de Palma F, Dermer CD, Di Venere L, Silva EDE, Drell PS, Drlica-Wagner A, Falletti L, Favuzzi C, Fegan SJ, Ferrara EC, Focke WB, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giordano F, Giroletti M, Glanzman T, Godfrey G, Gregoire T, Grenier IA, Grondin MH, Grove JE, Guiriec S, Hadasch D, Hanabata Y, Harding AK, Hayashida M, Hayashi K, Hays E, Hewitt J, Hill AB, Horan D, Hou X, Hughes RE, Inoue Y, Jackson MS, Jogler T, Johannesson G, Johnson AS, Kamae T, Kawano T, Kerr M, Knodlseder J, Kuss M, Lande J, Larsson S, Latronico L, Lemoine-Goumard M, Longo F, Loparco F, Lovellette MN, Lubrano P, Marelli M, Massaro F, Mayer M, Mazziotta MN, McEnery JE, Mehault J, Michelson PF, Mitthumsiri W, Mizuno T, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nakamori T, Nemmen R, Nuss E, Ohsugi T, Okumura A, Orienti M, Orlando E, Ormes JF, Paneque D, Panetta JH, Perkins JS, Pesce-Rollins M, Piron F, Pivato G, Porter TA, Raino S, Rando R, Razzano M, Reimer A, Reimer O, Reposeur T, Ritz S, Roth M, Rousseau R, Parkinson PMS, Schulz A, Sgro C, Siskind EJ, Smith DA, Spandre G, Spinelli P, Suson DJ, Takahashi H, Takeuchi Y, Thayer JG, Thayer JB, Thompson DJ, Tibaldo L, Tibolla O, Tinivella M, Torres DF, Tosti G, Troja E, Uchiyama Y, Vandenbroucke J, Vasileiou V, Vianello G, Vitale V, Werner M, Winer BL, Wood KS, Yang Z, 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), 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 Toulouse III - Paul Sabatier (UT3), 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), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-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 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), Acero, F., Ackermann, M., Ajello, M., Allafort, A., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bechtol, K., Bellazzini, R., Blandford, R. D., Bloom, E. D., Bonamente, E., Bottacini, E., Brandt, T. J., Bregeon, J., Brigida, M., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Caraveo, P. A., Cecchi, C., Charles, E., Chaves, R. C. G., Chekhtman, A., Chiang, J., Chiaro, G., Ciprini, S., Claus, R., Cohen Tanugi, J., Conrad, J., Cutini, S., Dalton, M., D'Ammando, F., de Palma, F., Dermer, C. D., Di Venere, L., Silva, E. do Couto e., Drell, P. S., Drlica Wagner, A., Falletti, L., 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., Godfrey, G., Grégoire, T., Grenier, I. A., Grondin, M. H., Grove, J. E., Guiriec, S., Hadasch, D., Hanabata, Y., Harding, A. K., Hayashida, M., Hayashi, K., Hays, E., Hewitt, J., Hill, A. B., Horan, D., Hou, X., Hughes, R. E., Inoue, Y., Jackson, M. S., Jogler, T., Jóhannesson, G., Johnson, A. S., Kamae, T., Kawano, T., Kerr, M., Knödlseder, J., Kuss, M., Lande, J., Larsson, S., Latronico, L., Lemoine Goumard, M., Longo, Francesco, Loparco, F., Lovellette, M. N., Lubrano, P., Marelli, M., Massaro, F., Mayer, M., Mazziotta, M. N., Mcenery, J. E., Mehault, J., Michelson, P. F., Mitthumsiri, W., Mizuno, T., Monte, C., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Nakamori, T., Nemmen, R., Nuss, E., Ohsugi, T., Okumura, A., Orienti, M., Orlando, E., Ormes, J. F., Paneque, D., Panetta, J. H., Perkins, J. S., Pesce Rollins, M., Piron, F., Pivato, G., Porter, T. A., Rainò, S., Rando, R., Razzano, M., Reimer, A., Reimer, O., Reposeur, T., Ritz, S., Roth, M., Rousseau, R., Saz Parkinson, P. M., Schulz, A., Sgrò, C., Siskind, E. J., Smith, D. A., Spandre, G., Spinelli, P., Suson, D. J., Takahashi, H., Takeuchi, Y., Thayer, J. G., Thayer, J. B., Thompson, D. J., Tibaldo, L., Tibolla, O., Tinivella, M., Torres, D. F., Tosti, G., Troja, E., Uchiyama, Y., Vandenbroucke, J., Vasileiou, V., Vianello, G., Vitale, V., Werner, M., Winer, B. L., Wood, K. S., Yang, Z., 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), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), National Institute for Nuclear Physics (INFN), and 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)

Subjects
[PHYS.ASTR.HE]Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Astrophysics::High Energy Astrophysical Phenomena, Population, FOS: Physical sciences, Context (language use), Astrophysics, 01 natural sciences, law.invention, Telescope, Pulsar, law, 0103 physical sciences, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, education, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), education.field_of_study, 010308 nuclear & particles physics, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Astrophysics::Instrumentation and Methods for Astrophysics, Spectral density, Astronomy and Astrophysics, gamma rays: general, Galactic plane, Space and Planetary Science, ddc:520, Physics::Accelerator Physics, Astrophysics - High Energy Astrophysical Phenomena, general [gamma rays], Fermi Gamma-ray Space Telescope
Abstract

Pulsar wind nebulae (PWNe) have been established as the most populous class of TeV gamma-ray emitters. Since launch, the Fermi Large Area Telescope (LAT)identified five high-energy (100MeV, Comment: 72 pages, 13 figures

Published
2013
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135. The Second Fermi Large Area Telescope Catalog of Gamma-ray Pulsars

Author

G. Busetto, Brian L Winer, John J. Ruan, A. A. Moiseev, Eric Charles, Steven Ritz, D. J. Suson, Luca Baldini, Simon Johnston, F. Loparco, N. Renault, W. Mitthumsiri, Na Wang, Sylvain Guiriec, I. A. Grenier, James Chiang, Jeffrey D. Scargle, Roger W. Romani, Jürgen Knödlseder, S. Germani, K. S. Wood, P. Lubrano, M. Marelli, Jayashree Roy, R. Buehler, Jun Kataoka, Gloria Spandre, Ronaldo Bellazzini, A. S. Johnson, S. Cutini, Michael Kramer, T. Ohsugi, Eleonora Troja, Miranda Jackson, Maura McLaughlin, T. Reposeur, Peter F. Michelson, Marcello Giroletti, Francesco Longo, R. C. G. Chaves, Yasunobu Uchiyama, Johann Cohen-Tanugi, M. Orienti, Alex Drlica-Wagner, Dario Gasparrini, M. Hayashida, Sylvain Chaty, Nanda Rea, E. D. Bloom, Jean Ballet, A. Morselli, Xian Hou, V. Vitale, T. Jogler, Charles D. Dermer, R. N. Manchester, D. Parent, M. E. Monzani, Andrea Belfiore, Stefano Ciprini, Bhaswati Bhattacharyya, Gemma H. Janssen, R. Rousseau, J. Lande, Scott M. Ransom, Michael Keith, Luca Latronico, P. R. den Hartog, Gino Tosti, M. Mayer, Francesco Massaro, R. E. Hughes, A. W. Chen, A. B. Hill, L. R. Cominsky, Igor V. Moskalenko, Melissa Pesce-Rollins, J. G. Thayer, M. Burgay, Elisabetta Bissaldi, Olaf Reimer, Paul S. Ray, Holger J. Pletsch, M. Tinivella, T. L. Usher, M. E. DeCesar, Jason W. T. Hessels, Paulo C. C. Freire, G. A. Caliandro, Jan Conrad, Elizabeth C. Ferrara, Takeshi Nakamori, J. M. Casandjian, Terri Brandt, Hiromitsu Takahashi, André Schulz, Patrick Weltevrede, Andrew W. Strong, M. N. Mazziotta, D. Dumora, C. Favuzzi, J. Mehault, Christo Venter, A. De Angelis, P. Fusco, L. Guillemot, D. J. Thompson, T. H. Burnett, Diego F. Torres, A. A. Abdo, E. Orlando, Gregory Desvignes, W. N. Johnson, Gilles Theureau, L. Tibaldo, S. Murgia, M. T. Wolff, C. Cecchi, Alberto Sartori, T. Glanzman, F. Piron, Rodrigo Nemmen, Matthew Kerr, Matthew G. Baring, D. Horan, Giacomo Vianello, Fernando Camilo, L. Di Venere, Gudlaugur Johannesson, O. Tibolla, Masanori Ohno, D. L. Wood, E. Hays, Y. Hanabata, G. Pivato, M. Roth, F. Gargano, Alice K. Harding, Ismaël Cognard, Benjamin Stappers, Justin Vandenbroucke, Emanuele Bonamente, J. F. Ormes, Eugenio Bottacini, T. A. Porter, Guido Barbiellini, E. J. Siskind, David A. Smith, L. Falletti, Denis Bastieri, R. Claus, Marianne Lemoine-Goumard, Johan Bregeon, D. Hadasch, Ryan Shannon, A. Possenti, A. Reimer, J. H. Panetta, M. Razzano, S. Rainò, Eric V. Gotthelf, Tsunefumi Mizuno, Filippo D'Ammando, Julie McEnery, T. Kamae, M. Brigida, Stephen E. Thorsett, R. P. Johnson, G. Chiaro, J. E. Grove, P. M. Saz Parkinson, J. S. Perkins, Paolo Giommi, Marco Ajello, J. B. Thayer, S. Larsson, S. Buson, Nicola Giglietto, A. De Luca, M. N. Lovellette, P. A. Caraveo, Persis S. Drell, Alice Allafort, Roberto Mignani, Tyrel J. Johnson, R. A. Cameron, A. Chekhtman, R. Dubois, W. B. Focke, P. Spinelli, Seth Digel, Francesco Giordano, John W. Hewitt, P. Bruel, V. Vasileiou, Matthew Wood, G. Godfrey, F. de Palma, Andrew Lyne, M.-H. Grondin, Robert R. Rando, M. Pierbattista, Cristobal M. Espinoza, Omer Celik, A. Franckowiak, Stefan Funk, Zhenwei Yang, Carmelo Sgrò, E. Nuss, David Paneque, M. Kuss, 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), 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), 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), Unité Scientifique de la Station de Nançay (USN), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), 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)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-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), 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), FERMI, 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)-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), Istituto Nazionale di Fisica Nucleare, sezione di Bari (INFN, sezione di Bari), National Institute for Nuclear Physics (INFN), IEEC-CSIC, Universitat Autònoma de Barcelona [Barcelona] (UAB), Laboratoire d'Astrophysique de Grenoble (LAOG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), 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), Fermi-LAT, High Energy Astrophys. & Astropart. Phys (API, FNWI), Abdo AA, Ajello M, Allafort A, Baldini L, Ballet J, Barbiellini G, Baring MG, Bastieri D, Belfiore A, Bellazzini R, Bhattacharyya B, Bissaldi E, Bloom ED, Bonamente E, Bottacini E, Brandt TJ, Bregeon J, Brigida M, Bruel P, Buehler R, Burgay M, Burnett TH, Busetto G, Buson S, Caliandro GA, Cameron RA, Camilo F, Caraveo PA, Casandjian JM, Cecchi C, Celik O, Charles E, Chaty S, Chaves RCG, Chekhtman A, Chen AW, Chiang J, Chiaro G, Ciprini S, Claus R, Cognard I, Cohen-Tanugi J, Cominsky LR, Conrad J, Cutini S, DAmmando F, De Angelis A, DeCesar ME, De Luca A, Den Hartog PR, De Palma F, Dermer CD, Desvignes G, Digel SW, Di Venere L, Drell PS, Drlica-Wagner A, Dubois R, Dumora D, Espinoza CM, Falletti L, Favuzzi C, Ferrara EC, Focke WB, Franckowiak A, Freire PCC, Funk S, Fusco P, Gargano F, Gasparrini D, Germani S, Giglietto N, Giommi P, Giordano F, Giroletti M, Glanzman T, Godfrey G, Gotthelf EV, Grenier IA, Grondin MH, Grove JE, Guillemot L, Guiriec S, Hadasch D, Hanabata Y, Harding AK, Hayashida M, Hays E, Hessels J, Hewitt J, Hill AB, Horan D, Hou X, Hughes RE, Jackson MS, Janssen GH, Jogler T, Johannesson G, Johnson RP, Johnson AS, Johnson TJ, Johnson WN, Johnston S, Kamae T, Kataoka J, Keith M, Kerr M, Knodlseder J, Kramer M, Kuss M, Lande J, Larsson S, Latronico L, Lemoine-Goumard M, Longo F, Loparco F, Lovellette MN, Lubrano P, Lyne AG, Manchester RN, Marelli M, Massaro F, Mayer M, Mazziotta MN, McEnery JE, McLaughlin MA, Mehault J, Michelson PF, Mignani RP, Mitthumsiri W, Mizuno T, Moiseev AA, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nakamori T, Nemmen R, Nuss E, Ohno M, Ohsugi T, Orienti M, Orlando E, Ormes JF, Paneque D, Panetta JH, Parent D, Perkins JS, Pesce-Rollins M, Pierbattista M, Piron F, Pivato G, Pletsch HJ, Porter TA, Possenti A, Raino S, Rando R, Ransom SM, Ray PS, Razzano M, Rea N, Reimer A, Reimer O, Renault N, Reposeur T, Ritz S, Romani RW, Roth M, Rousseau R, Roy J, Ruan J, Sartori A, Parkinson PMS, Scargle JD, Schulz A, Sgro C, Shannon R, Siskind EJ, Smith DA, Spandre G, Spinelli P, Stappers BW, Strong AW, Suson DJ, Takahashi H, Thayer JG, Thayer JB, Theureau G, Thompson DJ, Thorsett SE, Tibaldo L, Tibolla O, Tinivella M, Torres DF, Tosti G, Troja E, Uchiyama Y, Usher TL, Vandenbroucke J, Vasileiou V, Venter C, Vianello G, Vitale V, Wang N, Weltevrede P, Winer BL, Wolff MT, Wood DL, Wood KS, Wood M, Yang Z, Abdo, A. A., Ajello, M., Allafort, A., Baldini, L., Ballet, J., BARBIELLINI AMIDEI, Guido, Baring, M. G., Bastieri, D., Belfiore, A., Bellazzini, R., Bhattacharyya, B., Bissaldi, Elisabetta, Bloom, E. D., Bonamente, E., Bottacini, E., Brandt, T. J., Bregeon, J., Brigida, M., Bruel, P., Buehle, R., Burgay, M., Burnett, T. H., Busetto, G., Buson, S., Caliandro, G. A., Cameron, R. A., Camilo, F., Caraveo, P. A., Casandjian, J. M., Cecchi, C., Çelik, Ö., Charles, E., Chaty, S., Chaves, R. C. G., Chekhtman, A., Chen, A. W., Chiang, J., Chiaro, G., Ciprini, S., Claus, R., Cognard, I., Cohen Tanugi, J., Cominsky, L. R., Conrad, J., Cutini, S., D'Ammando, F., de Angelis, A., Decesar, M. E., De Luca, A., den Hartog, P. R., de Palma, F., Dermer, C. D., Desvignes, G., Digel, S. W., Di Venere, L., Drell, P. S., Drlica Wagner, A., Dubois, R., Dumora, D., Espinoza, C. M., Falletti, L., Favuzzi, C., Ferrara, E. C., Focke, W. B., Franckowiak, A., Freire, P. C. C., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Germani, S., Giglietto, N., Giommi, P., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Gotthelf, E. V., Grenier, I. A., Grondin, M. H., Grove, J. E., Guillemot, L., Guiriec, S., Hadasch, D., Hanabata, Y., Harding, A. K., Hayashida, M., Hays, E., Hessels, J., Hewitt, J., Hill, A. B., Horan, D., Hou, X., Hughes, R. E., Jackson, M. S., Janssen, G. H., Jogler, T., Jóhannesson, G., Johnson, R. P., Johnson, A. S., Johnson, T. J., Johnson, W. N., Johnston, S., Kamae, T., Kataoka, J., Keith, M., Kerr, M., Knödlseder, J., Kramer, M., Kuss, M., Lande, J., Larsson, S., Latronico, L., Lemoine Goumard, M., Longo, Francesco, Loparco, F., Lovellette, M. N., Lubrano, P., Lyne, A. G., Manchester, R. N., Marelli, M., Massaro, F., Mayer, M., Mazziotta, M. N., Mcenery, J. E., Mclaughlin, M. A., Mehault, J., Michelson, P. F., Mignani, R. P., Mitthumsiri, W., Mizuno, T., Moiseev, A. A., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Nakamori, T., Nemmen, R., Nuss, E., Ohno, M., Ohsugi, T., Orienti, M., Orlando, E., Ormes, J. F., Paneque, D., Panetta, J. H., Parent, D., Perkins, J. S., Pesce Rollins, M., Pierbattista, M., Piron, F., Pivato, G., Pletsch, H. J., Porter, T. A., Possenti, A., Rainò, S., Rando, R., Ransom, S. M., Ray, P. S., Razzano, M., Rea, N., Reimer, A., Reimer, O., Renault, N., Reposeur, T., Ritz, S., Romani, R. W., Roth, M., Rousseau, R., Roy, J., Ruan, J., Sartori, A., Saz Parkinson, P. M., Scargle, J. D., Schulz, A., Sgrò, C., Shannon, R., Siskind, E. J., Smith, D. A., Spandre, G., Spinelli, P., Stappers, B. W., Strong, A. W., Suson, D. J., Takahashi, H., Thayer, J. G., Thayer, J. B., Theureau, G., Thompson, D. J., Thorsett, S. E., Tibaldo, L., Tibolla, O., Tinivella, M., Torres, D. F., Tosti, G., Troja, E., Uchiyama, Y., Usher, T. L., Vandenbroucke, J., Vasileiou, V., Venter, C., Vianello, G., Vitale, V., Wang, N., Weltevrede, P., Winer, B. L., Wolff, M. T., Wood, D. L., Wood, K. S., Wood, M., and Yang, Z.

Subjects
Catalogs pulsars, general stars, neutron, catalog, CRAB PULSAR, Astrophysics, 01 natural sciences, Pulsar wind nebula, general [pulsars], law.invention, neutron, Millisecond pulsar, law, catalogs, pulsars: general, stars: neutron, 010303 astronomy & astrophysics, general stars, Physics, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Astrophysics::Instrumentation and Methods for Astrophysics, WIND NEBULA, SUPERNOVA REMNANT G21.5-0.9, Astrophysics - High Energy Astrophysical Phenomena, PHOTON IMAGING CAMERA, [PHYS.ASTR.HE]Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], WHITE-DWARF COMPANION, MIDDLE-AGED PULSAR, DEEP OPTICAL OBSERVATIONS, NANCAY RADIO TELESCOPE, MILLISECOND PULSARS, LIGHT CURVES, Astrophysics::High Energy Astrophysical Phenomena, Catalogs pulsars, Astrophysics::Cosmology and Extragalactic Astrophysics, catalogs , pulsars: general , stars: neutron, Telescope, neutron [stars], Pulsar, 0103 physical sciences, Astrophysics::Galaxy Astrophysics, 010308 nuclear & particles physics, Crab Pulsar, catalogs – pulsars: general – stars: neutron, Astronomy, Astronomy and Astrophysics, Neutron star, Space and Planetary Science, ddc:520, X-ray pulsar, Fermi Gamma-ray Space Telescope
Abstract

This catalog summarizes 117 high-confidence > 0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data, through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emission for several young and millisecond pulsars. We compare the gamma-ray properties with those in the radio, optical, and X-ray bands. We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermi's selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions., Comment: 145 pages. Online files at http://fermi.gsfc.nasa.gov/ssc/data/access/lat/2nd_PSR_catalog/ A typo in the value of the photon flux for CTA 1 (PSR J0007+7303) has been corrected in Table 9. NASA ADS at http://cdsads.u-strasbg.fr/abs/2013ApJS..208...17A

Published
2013
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136. GMRT discovery of PSR J1544+4937, an eclipsing black-widow pulsar identified with a Fermi LAT source

Author

Simon Johnston, Matthew Kerr, K. S. Wood, Elizabeth C. Ferrara, Yashwant Gupta, Scott M. Ransom, Fernando Camilo, Alice K. Harding, Paul S. Ray, Dipankar Bhattacharya, Michael T. Wolff, Roger W. Romani, Bhaswati Bhattacharyya, Ismaël Cognard, P. M. Saz Parkinson, Peter F. Michelson, Michael Keith, D. L. Wood, P. R. den Hartog, Jayanta Roy, Inter-University Centre for Astronomy and Astrophysics [Pune] (IUCAA), Naval Research Laboratory (NRL), Hansen Experimental Physics Lab [Stanford] (HEPL), Stanford University, NASA Goddard Space Flight Center (GSFC), Columbia Astrophysics Laboratory (CAL), Columbia University [New York], Arecibo Observatory, National Astronomy and Ionosphere Center (NAIC), Cornell University [New York], 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), 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)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), 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), GSFC Astrophysics Science Division, CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Santa Cruz Institute for Particle Physics (SCIPP), University of California [Santa Cruz] (UCSC), University of California-University of California, PRAXIS Inc., and PRAXIS Inc

Subjects
Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, pulsars: individual (PSR J1544+4937), Ephemeris, 01 natural sciences, law.invention, Telescope, Pulsar, Millisecond pulsar, law, pulsars: general, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Circular orbit, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Eclipse, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Giant Metrewave Radio Telescope, 010308 nuclear & particles physics, binaries: eclipsing, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract

Using the Giant Metrewave Radio Telescope (GMRT) we performed deep observations to search for radio pulsations in the directions of unidentified Fermi Large Area Telescope (LAT) gamma-ray sources. We report the discovery of an eclipsing black-widow millisecond pulsar, PSR J1544+4937, identified with the un-cataloged gamma-ray source Fermi J1544.2+4941. This 2.16 ms pulsar is in a 2.9 hours compact circular orbit with a very low-mass companion (Mc > 0.017 Msun). At 322 MHz this pulsar is found to be eclipsing for 13% of its orbit, whereas at 607 MHz the pulsar is detected throughout the low-frequency eclipse phase. Variations in the eclipse ingress phase are observed, indicating a clumpy and variable eclipsing medium. Moreover, additional short-duration absorption events are observed around the eclipse boundaries. Using the radio timing ephemeris we were able to detect gamma-ray pulsations from this pulsar, confirming it as the source powering the gamma-ray emission., 15 pages, 4 figures, 1 table, accepted for publication in ApJ Letters

Published
2013
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137. On the 110 keV Feature from A0535+26: Direct Evidence for a Near-critical Magnetic Field

Author

Rafael A. Araya and Alice K. Harding

Subjects
Physics, Field (physics), Scattering, Astrophysics (astro-ph), Cyclotron, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Spectral line, law.invention, Magnetic field, Cross section (physics), Space and Planetary Science, law, Harmonic, Atomic physics, Line (formation)
Abstract

A recent high resolution measurement of an absorption line at 110 keV in the phase-averaged spectrum of A0535+26 (Grove et al. 1994) and the conspicuous absence of a previously reported harmonic feature at around 50 keV (Kendziorra et al. 1992, 1994) are indicative of cyclotron scattering in a magnetic field of about $10^{13}$G. However, controversy has risen over whether a lower field scenario may account for the alleged absence or weakness of a lower energy fundamental harmonic feature. This work explores these two alternatives through the generation of theoretical cyclotron spectra. For lower field models, a cylindrical geometry of the line forming region and the strong angle dependence of the cross section for resonant scattering conspire to fill in a first harmonic at around 57 keV. Higher field models (B $\simeq$ 10.75 TG), however, yield significantly better fits (${\cal X}^2_{low}/{\cal X}^2_{high} \sim 71$), thus strengthening the case for a near-critical field ($B_{crit} \simeq 44$ TG). Phase-resolved OSSE spectra are not yet available but would greatly help in resolving this issue., Comment: 15 pages (AASTEX) + 2 figures (uuencoded, compressed ps), to be published in ApJ Letters, May 20, 1996

Published
1996
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138. Gamma-Ray Pulsar Emission Models

Author

Alice K. Harding

Subjects
Physics, Spectral index, Pulsar, Observatory, Millisecond pulsar, Astrophysics::High Energy Astrophysical Phenomena, Detector, Gamma ray, Astrophysics, Sensitivity (control systems), Radiation
Abstract

With the increased sensitivity of gamma-ray detectors on the Compton Gamma-Ray Observatory (CGRO) the number of presently known gamma-ray pulsars has grown. The new detections are beginning to provide clues to the origin of the high-energy radiation in the form of emerging patterns and correlations among observed quantities such as gamma-ray efficiency and spectral index vs. age. But there are still many questions about the location of the emission and its relation to the radio, optical and X-ray pulses. This paper will review models for gamma-ray emission from pulsars and will examine how well the detailed predictions of these models account for the existing observations.

Published
1996
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139. THE EFFECT OF AN OFFSET POLAR CAP DIPOLAR MAGNETIC FIELD ON THE MODELING OF THE VELA PULSAR’Sγ-RAY LIGHT CURVES

Author

Monica Barnard, Christo Venter, and Alice K. Harding

Subjects
Physics, 010308 nuclear & particles physics, Gamma ray, Astronomy and Astrophysics, Curvature, Light curve, 01 natural sciences, Magnetic field, Dipole, Pulsar, Space and Planetary Science, 0103 physical sciences, Emissivity, Atomic physics, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Magnetic dipole
Abstract

We performed geometric pulsar light curve modeling using static, retarded vacuum, and offset polar cap (PC) dipole $B$-fields (the latter is characterized by a parameter $\epsilon$), in conjunction with standard two-pole caustic (TPC) and outer gap (OG) emission geometries. The offset-PC dipole $B$-field mimics deviations from the static dipole (which corresponds to $\epsilon=0$). In addition to constant-emissivity geometric models, we also considered a slot gap (SG) $E$-field associated with the offset-PC dipole $B$-field and found that its inclusion leads to qualitatively different light curves. Solving the particle transport equation shows that the particle energy only becomes large enough to yield significant curvature radiation at large altitudes above the stellar surface, given this relatively low $E$-field. Therefore, particles do not always attain the radiation-reaction limit. Our overall optimal light curve fit is for the retarded vacuum dipole field and OG model, at an inclination angle $\alpha=78{_{-1}^{+1}}^{\circ}$ and observer angle $\zeta=69{_{-1}^{+2}}^{\circ}$. For this $B$-field, the TPC model is statistically disfavored compared to the OG model. For the static dipole field, neither model is significantly preferred. We found that smaller values of $\epsilon$ are favored for the offset-PC dipole field when assuming constant emissivity, and larger $\epsilon$ values favored for variable emissivity, but not significantly so. When multiplying the SG $E$-field by a factor of 100, we found improved light curve fits, with $\alpha$ and $\zeta$ being closer to best fits from independent studies, as well as curvature radiation reaction at lower altitudes., Comment: 42 pages, 17 figures

Published
2016
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140. Photon-photon opacity constraints for relativistically expanding gamma-ray burst sources

Author

Alice K. Harding and Matthew G. Baring

Subjects
Physics, Atmospheric Science, Photon, Opacity, Astrophysics::High Energy Astrophysical Phenomena, Solid angle, Gamma ray, Aerospace Engineering, Astronomy and Astrophysics, Astrophysics, Gamma-ray astronomy, Lorentz factor, symbols.namesake, Geophysics, Pair production, Space and Planetary Science, symbols, General Earth and Planetary Sciences, Gamma-ray burst
Abstract

Five bright gamma-ray bursts (GRBs) detected by the Burst and Transient Source Experiment (BATSE) have also been detected at higher energies by EGRET. Four are consistent with power-law spectra extending to energies as high as, in the case of GRB930131, 1 GeV. The fifth, and most recent, GRB940217, has a more complex spectrum, with one photon detected at 18 GeV, the most energetic GRB photon detection to date. The optical depth to photon-photon pair production in these sources is extremely large for distances more than about 10pc away if the radiation is emitted isotropically in the observer's frame. This optical depth can be dramatically reduced if the source is moving with a relativstic bulk Lorentz factor Gamma, and recent calculations for this situation have been limited to cases of a beam with opening angle 1 Gamma, or expansions of infinitely thin spherical shells. This paper presents our extension of the pair production otpical depth calculation in relativistically expanding sources to more general geometries, including shells of finite thickness and arbitrary opening angle. We find that the minimum bulk Lorentz factors for the Energy Gamma Ray Experiment Telescope (EGRET) sources to be optically thin, i.e. display no spectral attenuation, is only moderately dependent on the shell thickness and its opening solid angle; these new limits on required velocity for given geometries will aid in placing realistic constraints on GRB source models.

Published
1995
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141. Constraining γ -ray pulsar gap models with a simulated pulsar population

Author

Alice K. Harding, Peter L. Gonthier, M. Pierbattista, I. A. Grenier, 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), AstroParticule et Cosmologie (APC (UMR_7164)), 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), GSFC Laboratory for High Energy Astrophysics (LHEA), NASA Goddard Space Flight Center (GSFC), Universita di Torino, 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), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Population, FOS: Physical sciences, Astrophysics, 01 natural sciences, law.invention, Telescope, Pulsar, law, 0103 physical sciences, Population synthesis, education, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), [PHYS]Physics [physics], Beam diameter, education.field_of_study, 010308 nuclear & particles physics, Gamma ray, Astronomy and Astrophysics, Space and Planetary Science, Polar, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Fermi Gamma-ray Space Telescope
Abstract

With the large sample of young gamma-ray pulsars discovered by the Fermi Large Area Telescope (LAT), population synthesis has become a powerful tool for comparing their collective properties with model predictions. We synthesised a pulsar population based on a radio emission model and four gamma-ray gap models (Polar Cap, Slot Gap, Outer Gap, and One Pole Caustic) normalizing to the number of detected radio pulsars in select group of surveys. The luminosity and the wide beams from the outer gaps can easily account for the number of Fermi detections in 2 years of observations. The wide slot-gap beams requires an increase by a factor of ~10 of the predicted luminosity to produce a reasonable number of gamma-ray pulsars. Such large increases in the luminosity may be accommodated by implementing offset polar caps. The narrow polar-cap beams contribute at most only a handful of LAT pulsars. Standard distributions in birth location and pulsar spin-down power (Edot) fail to reproduce the LAT findings: all models under-predict the number of LAT pulsars with high Edot, and they cannot explain the high probability of detecting both the radio and gamma-ray beams at high Edot. The beaming factor remains close to 1 over 4 decades in Edot evolution for the slot gap whereas it significantly decreases with increasing age for the outer gaps. The evolution of the slot-gap luminosity with Edot is compatible with the large dispersion of gamma-ray luminosity seen in the LAT data. The stronger evolution predicted for the outer gap, which is linked to the polar cap heating by the return current, is apparently not supported by the LAT data. The LAT sample of gamma-ray pulsars therefore provides a fresh perspective on the early evolution of the luminosity and beam width of the gamma-ray emission from young pulsars, calling for thin and more luminous gaps., 23 pages, 21 figures, accepted for publication in A&A

Published
2012
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142. FERMI LARGE AREA TELESCOPE OBSERVATIONS OF THE SUPERNOVA REMNANT G8.7-0.1

Author

Hartmut Sadrozinski, R. A. Cameron, Stefano Ciprini, Marco Ajello, J. B. Thayer, Sho Nishino, Jay P. Norris, Akira Okumura, T. A. Porter, Pascal Bruel, T. Ohsugi, Eleonora Troja, Gloria Spandre, Gudlaugur Johannesson, Elliott D. Bloom, Alex Drlica-Wagner, K. Hayashi, D. Parent, S. Buson, E. Hays, R. Buehler, Luca Latronico, T. Glanzman, Johann Cohen-Tanugi, S. Murgia, Stephan Zimmer, Roger Blandford, F. Piron, Peter F. Michelson, Marcello Giroletti, Justin Vandenbroucke, M. Roth, Guido Barbiellini, Nicola Omodei, G. Godfrey, Zhenwei Yang, Carmelo Sgrò, Riccardo Rando, Yasuo Fukui, A. De Angelis, G. Tosti, R. Dubois, W. B. Focke, V. Pelassa, E. Nuss, David Paneque, M. Ohno, M. E. Monzani, M. Kuss, Alice K. Harding, P. Spinelli, Francesco Giordano, Hideaki Katagiri, F. de Palma, Melissa Pesce-Rollins, A. Van Etten, Igor V. Moskalenko, M. Frailis, Elizabeth C. Ferrara, G. A. Caliandro, Jonathan F. Ormes, Olaf Reimer, E. Do Couto E Silva, B. Berenji, Ryo Yamazaki, Giacomo Vianello, A. Morselli, Hiromitsu Takahashi, V. Vitale, D. Hadasch, Keith Bechtol, S. Rainò, M. Brigida, Tsunefumi Mizuno, Hajimu Yasuda, Francesco Longo, C. Favuzzi, Jürgen Knödlseder, E. Orlando, Takeshi Nakamori, J. M. Casandjian, A. Tramacere, R. Claus, Hiroaki Yamamoto, Hiroyasu Tajima, J. Bregeon, Ryosuke Itoh, Nicola Giglietto, P. L. Nolan, J. E. Grove, Yasushi Fukazawa, Takaaki Tanaka, A. P. Waite, S. Germani, Brian L Winer, Shiu-Hang Lee, Ronaldo Bellazzini, Andrea Lionetto, M. N. Lovellette, Dario Gasparrini, Diego F. Torres, Hidetoshi Kubo, P. A. Caraveo, Alice Allafort, P. Fusco, Persis S. Drell, Paolo Giommi, C. Monte, T. Kamae, V. Vasileiou, J. G. Thayer, T. L. Usher, A. A. Moiseev, Yasunobu Uchiyama, Jun Kataoka, S. J. Fegan, J. Mehault, Luca Baldini, A. Reimer, M. Naumann-Godo, Charles D. Dermer, E. J. Siskind, M. Pierbattista, A. S. Johnson, S. Cutini, Claudia Cecchi, F. Loparco, P. Wang, Denis Bastieri, Emanuele Bonamente, J. Lande, Sylvain Guiriec, K. S. Wood, L. Tibaldo, O. Tibolla, N. Vilchez, Y. Hanabata, F. Gargano, P. D. Smith, T. Reposeur, A. W. Borgland, T. Uehara, M. Ziegler, M. N. Mazziotta, A. Chekhtman, P. Lubrano, Eric Charles, D. J. Suson, Jean Ballet, Ajello, M., Allafort, A., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bechtol, K., Bellazzini, R., Berenji, B., Blandford, R. D., Bloom, E. D., Bonamente, E., Borgland, A. W., Bregeon, J., Brigida, M., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Caraveo, P. A., Casandjian, J. M., Cecchi, C., Charles, E., Chekhtman, A., Ciprini, S., Claus, R., Cohen Tanugi, J., Cutini, S., Angelis, A., Palma, F., Dermer, C. D., E. d. C., Drell, P. S., Drlica Wagner, A., Dubois, R., Favuzzi, C., Fegan, S. J., Ferrara, E. C., Focke, W. B., Frailis, M., Fukazawa, Y., Fukui, Y., Fusco, P., Gargano, F., Gasparrini, D., Germani, S., Giglietto, N., Giommi, P., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Grove, J. E., Guiriec, S., Hadasch, D., Hanabata, Y., Harding, A. K., Hayashi, K., Hays, E., Itoh, R., Johannesson, G., Johnson, A. S., Kamae, T., Katagiri, H., Kataoka, J., Kn\odlseder, J., Kubo, H., Kuss, M., Lande, J., Latronico, L., Lee, S., Lionetto, A. M., Longo, Francesco, Loparco, F., Lovellette, M. N., Lubrano, P., Mazziotta, M. N., Mehault, J., Michelson, P. F., Mizuno, T., Moiseev, A. A., Monte, C., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Nakamori, T., Naumann Godo, M., Nishino, S., Nolan, P. L., Norris, J. P., Nuss, E., Ohno, M., Ohsugi, T., Okumura, A., Omodei, N., Orlando, E., Ormes, J. F., Paneque, D., Parent, D., Pelassa, V., Pesce Rollins, M., Pierbattista, M., Piron, F., Porter, T. A., Rain\`o, S., Rando, R., Reimer, A., Reimer, O., Reposeur, T., Roth, M., Sadrozinski, H. F., Sgr\`o, C., Siskind, E. J., Smith, P. D., Spandre, G., Spinelli, P., Suson, D. J., Tajima, H., Takahashi, H., Tanaka, T., Thayer, J. G., Thayer, J. B., Tibaldo, L., Tibolla, O., Torres, D. F., Tosti, G., Tramacere, A., Troja, E., Uchiyama, Y., Uehara, T., Usher, T. L., Vandenbroucke, J., Etten, A., Vasileiou, V., Vianello, G., Vilchez, N., Vitale, V., Waite, A. P., Wang, P., Winer, B. L., Wood, K. S., Yamamoto, H., Yamazaki, R., Yang, Z., Yasuda, H., Ziegler, M., Zimmer, S., 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 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), 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), 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), GLAST, 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)-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), 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)), 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)-École polytechnique (X)-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)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), 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 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 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 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 Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.ASTR.HE]Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Astrophysics::High Energy Astrophysical Phenomena, Cosmic ray, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, acceleration of particles, cosmic rays, gamma rays, ISM, ISM: individual objects (G8.7–0.1, HESS J1804–216), ISM: supernova remnants, Spectral line, Particle decay, individual objects: G8.7{\ndash}0.1 HESS J1804{\ndash}216 [ISM], gamma rays: ISM, ISM: individual objects (G8.7?0.1, ISM [gamma rays], ISM: individual objects (G8.7?0.1, HESS J1804?216), Astronomy and Astrophysics, Space and Planetary Science, 0103 physical sciences, 14. Life underwater, Supernova remnant, ISM: individual objects (G8.7-0.1, 010303 astronomy & astrophysics, acceleration of particle, cosmic ray, Astrophysics::Galaxy Astrophysics, Acceleration of particles, ISM: individual objects (G8.7-0.1, HESS J1804-216), Physics, Spectral index, HESS J1804-216), 010308 nuclear & particles physics, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], supernova remnants [ISM], Astronomy, Gamma-ray astronomy, ISM: individual objects: G8.7{\ndash}0.1 HESS J1804{\ndash}216, Interstellar medium, HESS J1804?216), High Energy Physics::Experiment, Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract

We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) onboard the \emph{Fermi} Gamma-ray Space Telescope. An investigation of the relationship among G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially-connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV--100 GeV can be described by a broken power-law function with a break of 2.4 $\pm$ 0.6 (stat) $\pm$ 1.2 (sys) GeV, and photon indices of 2.10 $\pm$ 0.06 (stat) $\pm$ 0.10 (sys) below the break and 2.70 $\pm$ 0.12 (stat) $\pm$ 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7$-$0.1, and the molecular clouds, the decay of $\pi^{0}$s produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804$-$216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7$-$0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles., Comment: 42 pages, 5 figures. Accepted for publication in the Astrophysical Journal. Corresponding authors: Y. Hanabata, H. Katagiri

Published
2012
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143. Five new millisecond pulsars from a radio survey of 14 unidentified Fermi-LAT gamma-ray sources

Author

Michael Kramer, Michael Keith, Matthew Kerr, Jason W. T. Hessels, Elizabeth C. Ferrara, Alice K. Harding, Paul S. Ray, Simon Johnston, John Sarkissian, John Reynolds, Fernando Camilo, Scott M. Ransom, Tyrel J. Johnson, K. S. Wood, Lucas Guillemot, and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Proper motion, media_common.quotation_subject, Gamma ray, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Ephemeris, Light curve, Astrophysics - Astrophysics of Galaxies, Radio telescope, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Sky, Millisecond pulsar, Astrophysics of Galaxies (astro-ph.GA), Astrophysics - High Energy Astrophysical Phenomena, Solar and Stellar Astrophysics (astro-ph.SR), media_common, Fermi Gamma-ray Space Telescope
Abstract

We have discovered five millisecond pulsars (MSPs) in a survey of 14 unidentified Fermi-LAT sources in the southern sky using the Parkes radio telescope. PSRs J0101-6422, J1514-4946, and J1902-5105 reside in binaries, while PSRs J1658-5324 and J1747-4036 are isolated. Using an ephemeris derived from timing observations of PSR J0101-6422 (P =2.57 ms, DM=12 pc cm-3), we have detected {\gamma}-ray pulsations and measured its proper motion. Its {\gamma}-ray spectrum (a power law of {\Gamma} = 0.9 with a cutoff at 1.6 GeV) and efficiency are typical of other MSPs, but its radio and {\gamma}-ray light curves challenge simple geometric models of emission. The high success rate of this survey-enabled by selecting {\gamma}-ray sources based on their detailed spectral characteristics-and other similarly successful searches indicate that a substantial fraction of the local population of MSPs may soon be known., Comment: 6 pages, 3 figures, 2 tables, accepted by ApJL

Published
2012
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144. GAMMA-RAY ACTIVITY IN THE CRAB NEBULA: THE EXCEPTIONAL FLARE OF 2011 APRIL

Author

Martin C. Weisskopf, Stefan Funk, P. M. Saz Parkinson, Andrea Belfiore, Roger W. Romani, Matthew G. Baring, R. Buehler, Alice K. Harding, Francesco Massaro, Roger Blandford, Matthew Kerr, J. Chiang, Luca Baldini, Mn Mazziotta, J. E. Grove, Allyn F. Tennant, F. D'Ammando, E. Hays, Charles D. Dermer, E. Charles, Jeffrey D. Scargle, Buehler R, Scargle JD, Blandford RD, Baldini L, Baring MG, Belfiore A, Charles E, Chiang J, DAmmando F, Dermer CD, Funk S, Grove JE, Harding AK, Hays E, Kerr M, Massaro F, Mazziotta MN, Romani RW, Parkinson PMS, Tennant AF, and Weisskopf MC

Subjects
Physics, Astrophysics::High Energy Astrophysical Phenomena, Gamma ray, Flux, Astronomy and Astrophysics, Astrophysics, radiation mechanisms: non-thermal, gamma rays: stars, magnetohydrodynamics (MHD), law.invention, Telescope, Wavelength, Crab Nebula, ISM: supernova remnants, magnetic reconnection, pulsars: individual (Crab), Space and Planetary Science, law, gamma rays: stars , ISM: supernova remnants , magnetic reconnection , magnetohydrodynamics (MHD) , pulsars: individual (Crab) , radiation mechanisms: non-thermal, Spectral energy distribution, Fermi Gamma-ray Space Telescope, Flare, gamma rays: stars, ISM: supernova remnants, magnetic reconnection, magnetohydrodynamics: MHD, pulsars: individual: Crab, radiation mechanisms: non-thermal
Abstract

The Large Area Telescope on board the Fermi satellite observed a gamma-ray flare in the Crab Nebula lasting for approximately nine days in April of 2011. The source, which at optical wavelengths has a size of approximate to 11 lt-yr across, doubled its gamma-ray flux within eight hours. The peak photon flux was (186 +/- 6) x 10(-7) cm(-2) s(-1) above 100 MeV, which corresponds to a 30-fold increase compared to the average value. During the flare, a new component emerged in the spectral energy distribution, which peaked at an energy of (375 +/- 26) MeV at flare maximum. The observations imply that the emission region was likely relativistically beamed toward us and that variations in its motion are responsible for the observed spectral variability.

Published
2012

145. Gamma-Ray Light Curves from Pulsar Magnetospheres with Finite Conductivity

Author

Constantinos Kalapotharakos, Ioannis Contopoulos, Alice K. Harding, and Demosthenes Kazanas

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Field (physics), Astrophysics::High Energy Astrophysical Phenomena, Gamma ray, Magnetosphere, FOS: Physical sciences, Astronomy and Astrophysics, Curvature, Light curve, Computational physics, Lorentz factor, symbols.namesake, Pulsar, Space and Planetary Science, Physics::Space Physics, symbols, Astrophysics - High Energy Astrophysical Phenomena, Radiant intensity
Abstract

We investigate the shapes of \gamma-ray pulsar light curves using 3D pulsar magnetosphere models of finite conductivity. These models, covering the entire spectrum of solutions between vacuum and force-free magnetospheres, for the first time afford mapping the GeV emission of more realistic, dissipative pulsar magnetospheres. To this end we generate model light curves following two different approaches: (a) We employ the emission patterns of the slot and outer gap models in the field geometries of magnetospheres with different conductivity \sigma. (b) We define realistic trajectories of radiating particles in magnetospheres of different \sigma and compute their Lorentz factor under the influence of magnetospheric electric fields and curvature radiation-reaction; with these at hand we then calculate the emitted radiation intensity. The light curves resulting from these prescriptions are quite sensitive to the value of \sigma, especially in the second approach. While still not self-consistent, these results are a step forward in understanding the physics of pulsar \gamma-radiation., Comment: Submitted to the Astrophysical Journal Letters, 15 pages, 4 figures

Published
2012
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146. SGR J1550-5418 Bursts Detected with the Fermi Gamma-Ray Burst Monitor during its Most Prolific Activity

Author

Asaf Pe'er, Arne Rau, Chryssa Kouveliotou, Ersin Gogus, David Gruber, Matthew G. Baring, Adam Goldstein, A. von Kienlin, Jonathan Granot, Robert D. Preece, Charles A. Meegan, Paul M. Woods, Lex Kaper, Elisabetta Bissaldi, A. J. van der Horst, Misty Giles, Mark H. Finger, Anna L. Watts, W. S. Paciesas, P. N. Bhat, Yuki Kaneko, M. van der Klis, Sylvain Guiriec, Enrico Ramirez-Ruiz, Alice K. Harding, Julie McEnery, Neil Gehrels, N. M. Gorgone, Ralph A. M. J. Wijers, Colleen A. Wilson-Hodge, Vandiver Chaplin, Lin Lin, Melissa Gibby, Sheila McBreen, Stefanie Wachter, A. J., van der Horst, C., Kouveliotou, N. M., Gorgone, Y., Kaneko, M. G., Baring, S., Guiriec, E., Gogu, J., Granot, A. L., Watt, L., Lin, P. N., Bhat, Bissaldi, Elisabetta, V. L., Chaplin, M. H., Finger, N., Gehrel, M. H., Gibby, M. M., Gile, A., Goldstein, D., Gruber, A. K., Harding, L., Kaper, A., von Kienlin, M., van der Kli, S., Mcbreen, J., Mcenery, C. A., Meegan, W. S., Paciesa, A., Pe'Er, R. D., Preece, E., Ramirez Ruiz, A., Rau, S., Wachter, C., Wilson Hodge, P. M., Wood, R. A. M. J., Wijers, and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, PSR J1550-5418), FOS: Physical sciences, Context (language use), Astrophysics, Magnetar, 01 natural sciences, 7. Clean energy, Spectral line, 1E 1547.0-5408, individual: SGR J1550–5418 1E 1547.0–5408 PSR J1550–5418 [pulsars], stars: neutron, X-rays: bursts, pulsars: individual: SGR J1550–5418 1E 1547.0–5408 PSR J1550–5418, neutron [stars], 0103 physical sciences, Black-body radiation, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Bremsstrahlung, Astronomy and Astrophysics, Neutron star, 13. Climate action, Space and Planetary Science, Pulsars: individual (SGR J1550-5418, burst [X-rays], Gamma-ray burst, Astrophysics - High Energy Astrophysical Phenomena, Pulsars: individual (SGR J1550-5418, 1E 1547.0-5408, PSR J1550-5418), Fermi Gamma-ray Space Telescope
Abstract

We have performed detailed temporal and time-integrated spectral analysis of 286 bursts from SGR J1550-5418 detected with the Fermi Gamma-ray Burst Monitor (GBM) in January 2009, resulting in the largest uniform sample of temporal and spectral properties of SGR J1550-5418 bursts. We have used the combination of broadband and high time-resolution data provided with GBM to perform statistical studies for the source properties. We determine the durations, emission times, duty cycles and rise times for all bursts, and find that they are typical of SGR bursts. We explore various models in our spectral analysis, and conclude that the spectra of SGR J1550-5418 bursts in the 8-200 keV band are equally well described by optically thin thermal bremsstrahlung (OTTB), a power law with an exponential cutoff (Comptonized model), and two black-body functions (BB+BB). In the spectral fits with the Comptonized model we find a mean power-law index of -0.92, close to the OTTB index of -1. We show that there is an anti-correlation between the Comptonized Epeak and the burst fluence and average flux. For the BB+BB fits we find that the fluences and emission areas of the two blackbody functions are correlated. The low-temperature BB has an emission area comparable to the neutron star surface area, independent of the temperature, while the high-temperature blackbody has a much smaller area and shows an anti-correlation between emission area and temperature. We compare the properties of these bursts with bursts observed from other SGR sources during extreme activations, and discuss the implications of our results in the context of magnetar burst models., 13 pages, 10 figures, 2 tables; minor changes, ApJ in press

Published
2012

147. Gamma-ray light curves from realistic pulsar magnetospheres

Author

Ioannis Contopoulos, Demosthenes Kazanas, Constantinos Kalapotharakos, and Alice K. Harding

Subjects
Physics, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics, Light curve, Computational physics, Magnetic field, Lorentz factor, symbols.namesake, Dipole, Pulsar, Electric field, Dissipative system, symbols, Radiant intensity
Abstract

We present numerical models of dissipative 3D pulsar magnetospheres which are then used to model pulsar γ-ray light-curves (LC). Using a variety of prescriptions to relate the current density J to the fields E, B we produce families of solutions covering the entire spectrum between the vacuum retarded dipole (VRD) and the force-free solutions. These solutions provide also the distribution of electric fields, E∥ parallel to the magnetic field B, which accelerate the radiating particles. Using these detailed dissipative magnetospheric models we generate model LCs following two different approaches: (a) We define realistic trajectories of radiating particles in these dissipative magnetospheres and we compute their Lorentz factor under the influence of both the electric field E∥ and radiation-reaction effects; with these at hand we then calculate the radiation intensity as a function of pulsar phase to produce realistic LCs. (b) We use the standard emission arrangements of slot and outer gap models in the mag...

Published
2012
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148. Observations of Energetic High Magnetic Field Pulsars with the Fermi Large Area Telescope

Author

A. A. Abdo, Michael Kramer, M. E. DeCesar, F. Giordano, Michael Keith, Richard N. Manchester, Roger W. Romani, Cristobal M. Espinoza, Matthew Kerr, Eric V. Gotthelf, Paulo C. C. Freire, Patrick Weltevrede, H. A. Craig, Matthew G. Baring, Andrew Lyne, D. Parent, Ben Stappers, Andrea Possenti, David A. Smith, Karen Watters, M. Burgay, Alice K. Harding, Simon Johnston, Margaret A. Livingstone, George Hobbs, Lucas Guillemot, P. R. den Hartog, V. M. Kaspi, A. Noutsos, and Fernando Camilo

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Offset (computer science), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Field strength, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Light curve, Power law, Astrophysics - Astrophysics of Galaxies, law.invention, Telescope, Pulsar, Space and Planetary Science, law, Astrophysics of Galaxies (astro-ph.GA), Supernova remnant, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics::Galaxy Astrophysics, Fermi Gamma-ray Space Telescope
Abstract

We report the detection of gamma-ray pulsations from the high-magnetic-field rotation-powered pulsar PSR J1119-6127 using data from the Fermi Large Area Telescope. The gamma-ray light curve of PSR J1119-6127 shows a single, wide peak offset from the radio peak by 0.43 pm 0.02 in phase. Spectral analysis suggests a power law of index 1.0 pm 0.3 with an energy cut-off at 0.8 pm 0.2 GeV. The first uncertainty is statistical and the second is systematic. We discuss the emission models of PSR J1119-6127 and demonstrate that despite the object's high surface magnetic field---near that of magnetars---the field strength and structure in the gamma-ray emitting zone are apparently similar to those of typical young pulsars. Additionally, we present upper limits on the \gam-ray pulsed emission for the magnetically active PSR J1846-0258 in the supernova remnant Kesteven 75 and two other energetic high-B pulsars, PSRs J1718-3718 and J1734-3333. We explore possible explanations for the non-detection of these three objects, including peculiarities in their emission geometry., 13 pages, 6 figures. Accepted for publication in Astrophysical Journal

Published
2011

149. Toward a Realistic Pulsar Magnetosphere

Author

Constantinos Kalapotharakos, Alice K. Harding, Ioannis Contopoulos, and Demosthenes Kazanas

Subjects
Physics, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Magnetosphere, Astronomy and Astrophysics, Observable, Astrophysics, Electric charge, Physics - Plasma Physics, Magnetic field, Plasma Physics (physics.plasm-ph), Pulsar, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Electric field, Poynting vector, Magnetohydrodynamics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

We present the magnetic and electric field structures as well as the currents and charge densities of pulsar magnetospheres which do not obey the ideal condition, ${\bf E \cdot B =0}$. Since the acceleration of particles and the production of radiation requires the presence of an electric field component parallel to the magnetic field, ${\bf E}_\parallel$, the structure of non-Ideal pulsar magnetospheres is intimately related to the production of pulsar radiation. Therefore, knowledge of the structure of non-Ideal pulsar magnetospheres is important because their comparison (including models for the production of radiation) with observations will delineate the physics and the parameters underlying the pulsar radiation problem. We implement a variety of prescriptions that support nonzero values for ${\bf E}_\parallel$ and explore their effects on the structure of the resulting magnetospheres. We produce families of solutions that span the entire range between the vacuum and the (ideal) Force-Free Electrodynamic solutions. We also compute the amount of dissipation as a fraction of the Poynting flux for pulsars of different angles between the rotation and magnetic axes and conclude that this is at most 20-40% (depending on the non-ideal prescription) in the aligned rotator and 10% in the perpendicular one. We present also the limiting solutions with the property $J=\rho c$ and discuss their possible implication on the determination of the "on/off" states of the intermittent pulsars. Finally, we find that solutions with values of $J$ greater than those needed to null ${\bf E}_\parallel$ locally produce oscillations, potentially observable in the data., Comment: 26 pages, 12 figures, revised version. Accepted for publication in ApJ

Published
2011

150. Chandra Phase-Resolved X-ray Spectroscopy of the Crab Pulsar II

Author

Ronald F. Elsner, Werner Becker, Alice K. Harding, Vyacheslav E. Zavlin, Martin C. Weisskopf, Dmitry G. Yakovlev, Stephen L. O'Dell, and Allyn F. Tennant

Subjects
Physics, Spectral index, Crab Pulsar, Astrophysics::High Energy Astrophysical Phenomena, Extinction (astronomy), FOS: Physical sciences, Astronomy and Astrophysics, Optical polarization, Astrophysics, Position angle, Astrophysics - Astrophysics of Galaxies, Neutron star, Crab Nebula, Pulsar, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Galaxy Astrophysics
Abstract

We present a new study of the X-ray spectral properties of the Crab Pulsar. The superb angular resolution of the Chandra X-ray Observatory enables distinguishing the pulsar from the surrounding nebulosity. Analysis of the spectrum as a function of pulse phase allows the least-biased measure of interstellar X-ray extinction due primarily to photoelectric absorption and secondarily to scattering by dust grains in the direction of the Crab Nebula. We modify previous findings that the line-of-sight to the Crab is under-abundant in oxygen and provide measurements with improved accuracy and less bias. Using the abundances and cross sections from Wilms, Allen & McCray (2000) we find [O/H] = $(5.28 \pm 0.28)\times10^{-4}$ ($4.9 \times10^{-4}$ is solar abundance). We also measure for the first time the impact of scattering of flux out of the image by interstellar grains. We find $��_{\rm scat} = 0.147 \pm 0.043$. Analysis of the spectrum as a function of pulse phase also measures the X-ray spectral index even at pulse minimum --- albeit with increasing statistical uncertainty. The spectral variations are, by and large, consistent with a sinusoidal variation. The only significant variation from the sinusoid occurs over the same phase range as some rather abrupt behavior in the optical polarization magnitude and position angle. We compare these spectral variations to those observed in Gamma-rays and conclude that our measurements are both a challenge and a guide to future modeling and will thus eventually help us understand pair cascade processes in pulsar magnetospheres. The data were also used to set new, and less biased, upper limits to the surface temperature of the neutron star for different models of the neutron star atmosphere., 32 pages, 6 figures submitted to the Astrophysical journal

Published
2011

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