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19 results on '"Brian Grefenstette"'

1. The high energy X-ray probe (HEX-P): Resolving the nature of Sgr A* flares, compact object binaries and diffuse X-ray emission in the Galactic center and beyond

Author

Kaya Mori, Gabriele Ponti, Matteo Bachetti, Arash Bodaghee, Jonathan Grindlay, Jaesub Hong, Roman Krivonos, Ekaterina Kuznetsova, Shifra Mandel, Antonio Rodriguez, Giovanni Stel, Shuo Zhang, Tong Bao, Franz Bauer, Maïca Clavel, Benjamin Coughenour, Javier A. García, Julian Gerber, Brian Grefenstette, Amruta Jaodand, Bret Lehmer, Kristin Madsen, Melania Nynka, Peter Predehl, Ciro Salcedo, Daniel Stern, and John Tomsick

Subjects
galaxy: centre, black hole physics, X-rays: binaries, stars: cataclysmic variables, accretion, acceleration of particles, Astronomy, QB1-991, Geophysics. Cosmic physics, QC801-809
Abstract

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (

Published
2024
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2. The high energy X-ray probe (HEX-P): Galactic PeVatrons, star clusters, superbubbles, microquasar jets, and gamma-ray binaries

Author

Kaya Mori, Stephen Reynolds, Hongjun An, Aya Bamba, Roman Krivonos, Naomi Tsuji, Moaz Abdelmaguid, Jason Alford, Priyadarshini Bangale, Silvia Celli, Rebecca Diesing, Jordan Eagle, Chris L. Fryer, Stefano Gabici, Joseph Gelfand, Brian Grefenstette, Javier Garcia, Chanho Kim, Sajan Kumar, Ekaterina Kuznetsova, Brydyn Mac Intyre, Kristin Madsen, Silvia Manconi, Yugo Motogami, Hayato Ohsumi, Barbara Olmi, Jaegeun Park, Gabriele Ponti, Toshiki Sato, Ruo-Yu Shang, Daniel Stern, Yukikatsu Terada, Jooyun Woo, George Younes, and Andreas Zoglauer

Subjects
particle accelerators, Galactic PeVatrons, star clusters, superbubbles, microquasars, gamma-ray binaries, Astronomy, QB1-991, Geophysics. Cosmic physics, QC801-809
Abstract

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (

Published
2023
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3. The High Energy X-ray Probe (HEX-P): supernova remnants, pulsar wind nebulae, and nuclear astrophysics

Author

Stephen Reynolds, Hongjun An, Moaz Abdelmaguid, Jason Alford, Chris Fryer, Kaya Mori, Melania Nynka, Jaegeun Park, Yukikatsu Terada, Jooyun Woo, Aya Bamba, Priyadarshini Bangale, Rebecca Diesing, Jordan Eagle, Stefano Gabici, Joseph Gelfand, Brian Grefenstette, Javier Garcia, Chanho Kim, Sajan Kumar, Brydyn Mac Intyre, Kristin Madsen, Silvia Manconi, Yugo Motogami, Hayato Ohsumi, Barbara Olmi, Toshiki Sato, Ruo-Yu Shang, Daniel Stern, Naomi Tsuji, George Younes, and Andreas Zoglauer

Subjects
supernova remnants, pulsar wind nebulae, nuclear astrophysics, X-ray astrophysics, future missions frontiers, Astronomy, QB1-991, Geophysics. Cosmic physics, QC801-809
Abstract

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (

Published
2023
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4. The high energy X-ray probe: resolved X-ray populations in extragalactic environments

Author

Bret D. Lehmer, Kristen Garofali, Breanna A. Binder, Francesca Fornasini, Neven Vulic, Andreas Zezas, Ann Hornschemeier, Margaret Lazzarini, Hannah Moon, Toni Venters, Daniel Wik, Mihoko Yukita, Matteo Bachetti, Javier A. García, Brian Grefenstette, Kristin Madsen, Kaya Mori, and Daniel Stern

Subjects
early-type galaxies (429), star formation (1569), starburst galaxies (1570), X-ray binary stars (1811), X-ray astronomy (1810), compact objects (288), Astronomy, QB1-991, Geophysics. Cosmic physics, QC801-809
Abstract

We construct simulated galaxy data sets based on the High Energy X-ray Probe (HEX-P) mission concept to demonstrate the significant advances in galaxy science that will be yielded by the HEX-P observatory. The combination of high spatial resolution imaging ( 8 Universe.

Published
2023
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5. NuSTAR Observations of Abell 665 and 2146: Constraints on Nonthermal Emission

Author

Randall A. Rojas Bolivar, Daniel R. Wik, Ayşegül Tümer, Fabio Gastaldello, Julie Hlavacek-Larrondo, Paul Nulsen, Valentina Vacca, Grzegorz Madejski, Ming Sun, Craig L. Sarazin, Jeremy Sanders, Damiano Caprioli, Brian Grefenstette, and Niels-Jorgen Westergaard

Subjects
Galaxy clusters, Abell clusters, Intracluster medium, Non-thermal radiation sources, Astronomical radiation sources, X-ray astronomy, Astrophysics, QB460-466
Abstract

Observations from past missions such as RXTE and Beppo-SAX suggested the presence of inverse Compton (IC) scattering at hard X-ray energies within the intracluster medium of some massive galaxy clusters. In subsequent years, observations by, e.g., Suzaku, and now NuSTAR, have not been able to confirm these detections. We report on NuSTAR hard X-ray searches for IC emission in two massive galaxy clusters, A665 and A2146. To constrain the global IC flux in these two clusters, we fit global NuSTAR spectra with three models: single (1T) and two-temperature (2T) models, and a 1T plus power-law component (T+IC). The temperature components are meant to characterize the thermal ICM emission, while the power law represents the IC emission. We find that the 3–30 keV A665 and 3–20 keV A2146 spectra are best described by thermal emission alone, with average global temperatures of kT = (9.15 ± 0.1) keV for A665 and kT = (8.29 ± 0.1) keV for A 2146. We constrain the IC flux to F _NT 0.14 μ G and >0.011 μ G for A665 and A2146, respectively.

Published
2023
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6. Measuring the Cosmic X-Ray Background in 3–20 KeV with Stray Light from NuSTAR

Author

Steven Rossland, Daniel R. Wik, Brian Grefenstette, Nico Cappelluti, Francesca Civano, Fabio Gastaldello, Roberto Gilli, Fiona Harrison, Ann Hornschemeier, Ryan Hickox, Roman Krivonos, Kristin Madsen, Silvano Molendi, Andrew Ptak, Daniel Stern, and Andreas Zoglauer

Subjects
Cosmic background radiation, Active galactic nuclei, Diffuse x-ray background, Astronomy data analysis, X-ray surveys, Astronomy, QB1-991
Abstract

By characterizing the contribution of stray light to large data sets from the CXB Measurement X-ray observatory collected over 2012–2017, we report a measurement of the cosmic X-ray background (CXB) in the 3–20 keV energy range. These data represent ∼20% sky coverage while avoiding Galactic ridge X-ray emission and are less weighted by deep survey fields than previous measurements with CXB Measurement. Images in narrow energy bands are stacked in detector space and spatially fit with a model representing the stray light and uniform pattern expected from the CXB and the instrumental background, respectively. We establish baseline flux values from Earth-occulted data and validate the fitting method on stray-light observations of the Crab, which further serve to calibrate the resulting spectra. We present independent spectra of the CXB with the focal plane module FPMA and FPMB detector arrays, which are in excellent agreement with the canonical characterization by HEAO 1 and are 10% lower than most subsequent measurements: ${F}_{3-20\,\mathrm{keV}}^{\mathrm{FPMA}}=2.63\times {10}^{-11}\,\mathrm{erg}\,{{\rm{s}}}^{-1}\,{\mathrm{cm}}^{-2}\,{\deg }^{-2}$ and ${F}_{3\mbox{--}20\,\mathrm{keV}}^{\mathrm{FPMB}}\,=2.58\times {10}^{-11}\,\mathrm{erg}\,{{\rm{s}}}^{-1}\,{\mathrm{cm}}^{-2}\,{\deg }^{-2}$ . We discuss these results in light of previous measurements of the CXB and consider the impact of systematic uncertainties on our spectra.

Published
2023
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8. SRGA J181414.6-225604: A New Galactic Symbiotic X-Ray Binary Outburst Triggered by an Intense Mass-loss Episode of a Heavily Obscured Mira Variable

Author

Kishalay De, Ilya Mereminskiy, Roberto Soria, Charlie Conroy, Erin Kara, Shreya Anand, Michael C. B. Ashley, Martha L. Boyer, Deepto Chakrabarty, Brian Grefenstette, Matthew J. Hankins, Lynne A. Hillenbrand, Jacob E. Jencson, Viraj Karambelkar, Mansi M. Kasliwal, Ryan M. Lau, Alexander Lutovinov, Anna M. Moore, Mason Ng, Christos Panagiotou, Dheeraj R. Pasham, Andrey Semena, Robert Simcoe, Jamie Soon, Gokul P. Srinivasaragavan, Tony Travouillon, and Yuhan Yao

Published
2022
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9. NuSTAR Measurement of the Cosmic X-ray Background in the 3–20 keV Energy Band

Author

Roman Krivonos, Daniel Wik, Brian Grefenstette, Kristin Madsen, Kerstin Perez, Steven Rossland, Sergey Sazonov, and Andreas Zoglauer

Subjects
Astronomy
Abstract

We present measurements of the intensity of the cosmic X-ray background (CXB) with the Nuclear Spectroscopic Telescope Array (NuSTAR) telescope in the 3–20 keV energy range. Our method uses spatial modulation of the CXB signal on the NuSTAR detectors through the telescope’s side aperture. Based on the NuSTAR observations of selected extragalactic fields with a total exposure of 7 Ms, we have estimated the CXB 3–20 keV flux to be 2.8×10−11erg s−1cm−2deg−2, which is∼8 per cent higher than that measured withHEAO-1and consistent with the INTEGRAL measurement. The inferred CXB spectral shape in the3–20 keV energy band is consistent with the canonical model of Gruber et al. We demonstrate that the spatially modulated CXB signal measured by NuSTAR is not contaminated by systematic noise and is limited by photon statistics. The measured relative scatter of the CXB intensity between different sky directions is compatible with cosmic variance, which opens new possibilities for studying CXB anisotropy over the whole sky with NuSTAR.

Published
2021
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11. Effective area calibration of the Nuclear Spectroscopic Telescope Array

Author

Kristin K. Madsen, Karl Forster, Brian Grefenstette, Fiona A. Harrison, and Hiromasa Miyasaka

Subjects
Space and Planetary Science, Control and Systems Engineering, Mechanical Engineering, Astronomy and Astrophysics, Instrumentation, Electronic, Optical and Magnetic Materials
Abstract

We present here the updated calibration of the Nuclear Spectroscopic Telescope Array, which was performed using data on the Crab accumulated over the last nine years in orbit. The basis for this new calibration contains over 250 ks of focused Crab observations (imaged through the optics) and over 500 ks of stray-light (SL) Crab observations (not imaged through optics). We measured an epoch averaged spectrum of the SL Crab data and define a canonical Crab spectrum of Γ = 2.103 ± 0.001 and N = 9.69 ± 0.02 keV⁻¹ cm⁻² s⁻¹ at 1 keV, which we use as our calibration standard. This calibration released in the Calibration Data Base update 20211020 provides significant updates to: (1) the detector absorption component, (2) the detector response function, and (3) the effective area vignetting function. The calibration improves agreement between FPMA and FPMB across detectors with a standard deviation of 1.7% for repeat observations between off-axis angles of 1' to 4'. As a consequence of the measured SL observations, the absolute flux of the instrument has increased by 5% to 15%, with 5% below 1' off-axis angle, 10% between 1 and 2', and 15% above 4'.

Published
2022

12. Observation and origin of non-thermal hard X-rays from Jupiter

Author

Kaya Mori, Charles Hailey, Gabriel Bridges, Shifra Mandel, Amani Garvin, Brian Grefenstette, William Dunn, Benjamin J. Hord, Graziella Branduardi-Raymont, John Clarke, Caitriona Jackman, Melania Nynka, and Licia Ray

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::High Energy Astrophysical Phenomena, Physics::Space Physics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Earth and Planetary Astrophysics
Abstract

Electrons accelerated on Earth by a rich variety of wave scattering or stochastic processes generate hard non-thermal X-ray bremsstrahlung up to >~ 1 MeV and power Earth's various types of aurorae. Although Jupiter's magnetic field is an order of magnitude larger than Earth's, space-based telescopes have previously detected X-rays only up to ~7 keV. On the basis of theoretical models of the Jovian auroral X-ray production, X-ray emission in the ~2-7 keV band has been interpreted as thermal (arising from electrons characterized by a Maxwell-Boltzmann distribution) bremsstrahlung. Here we report the observation of hard X-rays in the 8-20 keV band from the Jovian aurorae, obtained with the NuSTAR X-ray observatory. The X-rays fit to a flat power-law model with slope 0.60+/-0.22 - a spectral signature of non-thermal, hard X-ray bremsstrahlung. We determine the electron flux and spectral shape in the keV to MeV energy range using coeval in situ measurements by the Juno spacecraft's JADE and JEDI instruments. Jovian electron spectra of the form we observe have previously been interpreted to arise in stochastic acceleration, rather than coherent acceleration by electric fields. We reproduce the X-ray spectral shape and approximate flux observed by NuSTAR, and explain the non-detection of hard X-rays by Ulysses, by simulating the non-thermal population of electrons undergoing precipitating electron energy loss, secondary electron generation and bremsstrahlung emission in a model Jovian atmosphere. The results highlight the similarities between the processes generating hard X-ray auroras on Earth and Jupiter, which may be occurring on Saturn, too., 39 pages, 6 figures, 2 tables. Published in Nature Astronomy (https://www.nature.com/articles/s41550-021-01594-8)

Published
2022

13. First indirect detection constraints on axions in the Solar basin

Author

William DeRocco, Shalma Wegsman, Brian Grefenstette, Junwu Huang, and Ken Van Tilburg

Subjects
High Energy Physics - Phenomenology, High Energy Physics::Theory, High Energy Physics - Phenomenology (hep-ph), Astrophysics - Solar and Stellar Astrophysics, Physics::Instrumentation and Detectors, Astrophysics::High Energy Astrophysical Phenomena, General Physics and Astronomy, Astrophysics::Solar and Stellar Astrophysics, FOS: Physical sciences, Astrophysics::Earth and Planetary Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

Axions with masses of order keV can be produced in great abundance within the Solar core. The majority of Sun-produced axions escape to infinity, but a small fraction of the flux is produced with speeds below the escape velocity. Over time, this process populates a basin of slow-moving axions trapped on bound orbits. These axions can decay to two photons, yielding an observable signature. We place the first limits on this solar basin of axions using recent quiescent solar observations made by the NuSTAR X-ray telescope. We compare three different methodologies for setting constraints, and obtain world-leading limits for axions with masses between 5 and 30 keV, in some cases improving on stellar cooling bounds by more than an order of magnitude in coupling., Comment: 15 pages, 15 figures

Published
2022
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15. High-entropy ejecta plumes in Cassiopeia A from neutrino-driven convection

Author

Toshiki, Sato, Keiichi, Maeda, Shigehiro, Nagataki, Takashi, Yoshida, Brian, Grefenstette, Brian J, Williams, Hideyuki, Umeda, Masaomi, Ono, and John P, Hughes

Abstract

Recent multi-dimensional simulations suggest that high-entropy buoyant plumes help massive stars to explode

Published
2020

16. Eta Carinae's Thermal X-ray Tail Measured with

Author

Kenji, Hamaguchi, Michael F, Corcoran, Theodore R, Gull, Hiromitsu, Takahashi, Brian, Grefenstette, Takayuki, Yuasa, Martin, Stuhlinger, Christopher, Russell, Anthony F J, Moffat, Thomas, Madura, Noel D, Richardson, Jose, Groh, Julian, Pittard, and Stan, Owocki

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Article
Abstract

The evolved, massive highly eccentric binary system, η Car, underwent a periastron passage in the summer of 2014. We obtained two coordinated X-ray observations with XMM-Newton and NuSTAR during the elevated X-ray flux state and just before the X-ray minimum flux state around this passage. These NuSTAR observations clearly detected X-ray emission associated with η Car extending up to ~50 keV for the first time. The NuSTAR spectrum above 10 keV can be fit with the bremsstrahlung tail from a kT ~6 keV plasma. This temperature is ΔkT ~2 keV higher than those measured from the iron K emission line complex, if the shocked gas is in collisional ionization equilibrium. This result may suggest that the companion star’s pre-shock wind velocity is underestimated. The NuSTAR observation near the X-ray minimum state showed a gradual decline in the X-ray emission by 40% at energies above 5 keV in a day, the largest rate of change of the X-ray flux yet observed in individual η Car observations. The column density to the hardest emission component, N(H) ~10(24) H cm(−2), marked one of the highest values ever observed for η Car, strongly suggesting the increased obscuration of the wind-wind colliding X-ray emission by the thick primary stellar wind prior to superior conjunction. Neither observation detected the power-law component in the extremely hard band that INTEGRAL and Suzaku observed prior to 2011. The power-law source might have faded before these observations.

Published
2020

17. The 2017 Failed Outburst of GX 339–4: Relativistic X-Ray Reflection near the Black Hole Revealed by NuSTAR and Swift Spectroscopy.

Author

Javier A. García, John A. Tomsick, Navin Sridhar, Victoria Grinberg, Riley M. T. Connors, Jingyi Wang, James F. Steiner, Thomas Dauser, Dominic J. Walton, Yanjun Xu, Fiona A. Harrison, Karl Foster, Brian Grefenstette, Kristin Madsen, and Andrew Fabian

Subjects
X-ray reflection, BLACK holes, BINARY black holes, SPECTRUM analysis, ACCRETION disks, GRAVITATIONAL waves, HAWKING radiation
Abstract

We report on the spectroscopic analysis of the black hole binary GX 339−4 during its recent 2017–2018 outburst, observed simultaneously by the Swift and NuSTAR observatories. Although during this particular outburst the source failed to make state transitions, and despite Sun constraints during the peak luminosity, we were able to trigger four different observations sampling the evolution of the source in the hard state. We show that even for the lowest-luminosity observations the NuSTAR spectra show clear signatures of X-ray reprocessing (reflection) in an accretion disk. Detailed analysis of the highest signal-to-noise spectra with our family of relativistic reflection models relxill indicates the presence of both broad and narrow reflection components. We find that a dual-lamppost model provides a superior fit when compared to the standard single lamppost plus distant neutral reflection. In the dual-lamppost model two sources at different heights are placed on the rotational axis of the black hole, suggesting that the narrow component of the Fe K emission is likely to originate in regions far away in the disk, but still significantly affected by its rotational motions. Regardless of the geometry assumed, we find that the inner edge of the accretion disk reaches a few gravitational radii in all our fits, consistent with previous determinations at similar luminosity levels. This confirms a very low degree of disk truncation for this source at luminosities above ∼1% Eddington. Our estimates of Rin reinforce the suggested behavior for an inner disk that approaches the innermost regions as the luminosity increases in the hard state. [ABSTRACT FROM AUTHOR]

Published
2019
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18. All-sky Medium Energy Gamma-ray Observatory: Exploring the Extreme Multimessenger Universe

Author

Julie McEnery, Alexander van der Horst, Alberto Dominguez, Alexander Moiseev, Alexandre Marcowith, Alice Harding, Amy Lien, Andrea Giuliani, Andrew Inglis, Stefano Ansoldi, Antonio Stamerra, Antonios Manousakis, Andy Strong, Cosimo Bambi, Barbara Patricelli, Matthew Baring, Juan Abel Barrio, Denis Bastieri, Brian Fields, John Beacom, Volker Beckmann, Wlodek Bednarek, Bindu Rani, Steven Boggs, Aleksey Bolotnikov, Brad Cenko, S., Jim Buckley, Brian Grefenstette, Michelle Hui, Carlotta Pittori, Chanda Prescod-Weinstein, Chris Shrader, Christian Gouiffes, Carolyn Kierans, Colleen Wilson-Hodge, Ammando, Filippo D., Daniel Castro, Daniel Kocveski, Dario Gasparrini, David Thompson, David Williams, Alessandro De Angelis, Denis Bernard, Seth Digel, Daniel Morcuende, Eric Charles, Elisabetta Bissaldi, Elizabeth Hays, Elizabeth Ferrara, Enrico Bozzo, Eric Grove, Eric Wulf, Eugenio Bottacini, Ezio Caroli, Fabian Kislat, Foteini Oikonomou, Francesco Giordano, Francesco Longo, Chris Fryer, Yasushi Fukazawa, Markos Georganopoulos, Georgia De Nolfo, Giacomo Vianello, Gottfried Kanbach, George Younes, Harsha Blumer, Dieter Hartmann, Margarita Hernanz, Hiromitsu Takahashi, Hui Li, Ivan Agudo, Igor Moskalenko, Inga Stumke, Isabelle Grenier, Jacob Smith, James Rodi, Jeremy Perkins, Joseph Gelfand, Jamie Holder, Jurgen Knodlseder, Joachim Kopp, Jean-Philippe Lenain, José-Manuel Álvarez, Jessica Metcalfe, John Krizmanic, Stephen, John B., Jack Hewitt, John Mitchell, Pat Harding, John Tomsick, Judith Racusin, Justin Finke, Oleg Kargaltsev, Klimenko, Alexei V., Henric Krawczynski, Karl Smith, Hidetoshi Kubo, Leonardo Di Venere, Lea Marcotulli, Jan Lommler, Lucas Parker, Luca Baldini, Luca Foffano, Luca Zampieri, Luigi Tibaldo, Maria Petropoulou, Marco Ajello, Manuel Meyer, Marcos López, Marc McConnell, Markus Boettcher, Martina Cardillo, Manel Martinez, Matthew Kerr, Nicola Mazziotta, M., Mattia Di Mauro, Matthew Wood, Eileen Meyer, Michael Briggs, Michaël De Becker, Michael Lovellette, Michele Doro, Sanchez-Conde, Miguel A., Michael Moss, Tsunefumi Mizuno, Marc Ribó, Kazuhiro Nakazawa, Naoko Kurahashi Neilson, Natalia Auricchio, Nicola Omodei, Uwe Oberlack, Masanori Ohno, Elena Orlando, Nepomuk Otte, Paolo Coppi, Peter Bloser, Haocheng Zhang, Philippe Laurent, Martin Pohl, Elisa Prandini, Peter Shawhan, Regina Caputo, Riccardo Campana, Riccardo Rando, Richard Woolf, Robert Johnson, Roberto Mignani, Roland Walter, Roopesh Ojha, Rui Curado da Silva, Stefano Dietrich, Stefan Funk, Silvia Zane, Sonia Anton, Sara Buson, Sara Cutini, Pablo Saz Parkinson, Richard Schirato, Sean Griffin, Kaufmann, S., Lukasz Stawarz, Stefano Ciprini, Stefano Del Sordo, Sam Jones, Sylvain Guiriec, Hiro Tajima, Teddy Cheung, Lih-Sin The, Tonia Venters, Troy Porter, Tim Linden, Ulisses Barres, Paliya, Vaidehi S., Vladimir Bozhilov, Tom Vestrand, Vincent Tatischeff, Wenlei Chen, Xilu Wang, Yasuyuki Tanaka, Lucas Uhm, Bing Zhang, Stephan Zimmer, Andreas Zoglauer, Zorawar Wadiasingh, NASA Goddard Space Flight Center (GSFC), Universidad Complutense de Madrid = Complutense University of Madrid [Madrid] (UCM), Clemson University, Centros de Laseres Pulsados, Universidade de Aveiro, Istituto Nazionale di Fisica Nucleare [Pisa] (INFN), Istituto Nazionale di Fisica Nucleare (INFN), Fudan University [Shanghai], Rice University [Houston], Centro Brasileiro de Pesquisas Físicas (CBPF), Ministério da Ciência e Tecnologia, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), 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), Los Alamos National Laboratory (LANL), West Virginia University [Morgantown], North-West University [South Aftrica] (NWU), University of California [San Diego] (UC San Diego), University of California (UC), Brookhaven National Laboratory [Upton, NY] (BNL), UT-Battelle, LLC-Stony Brook University [SUNY] (SBU), State University of New York (SUNY)-State University of New York (SUNY)-U.S. Department of Energy [Washington] (DOE), Софийски университет = Sofia University, Université de Genève = University of Geneva (UNIGE), University of Alabama in Huntsville (UAH), Washington University in Saint Louis (WUSTL), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, SLAC National Accelerator Laboratory (SLAC), Stanford University, Naval Research Laboratory (NRL), Agenzia Spaziale Italiana (ASI), Yale University [New Haven], Universidade de Coimbra [Coimbra], ASI Science Data Center (ASDC), Italian Space Agency, Istituto Nazionale di Fisica Nucleare, Sezione di Perugia (INFN, Sezione di Perugia), Istituto di Radioastronomia [Bologna] (IRA), Istituto Nazionale di Astrofisica (INAF), Université de Liège, CNR Institute of Atmospheric Sciences and Climate (ISAC), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), University of Illinois System, Hiroshima University, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), New York University [New York] (NYU), NYU System (NYU), University of Maryland [Baltimore County] (UMBC), University of Maryland System, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), California Institute of Technology (CALTECH), 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), The George Washington University (GW), University of North Florida [Jacksonville] (UNF), University of Delaware [Newark], NASA Marshall Space Flight Center (MSFC), University of California [Santa Cruz] (UC Santa Cruz), Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, Universidad Autónoma de Chiapas, University of New Hampshire (UNH), Institut de recherche en astrophysique et planétologie (IRAP), 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), Kyoto University, Drexel University, Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Stockholm University, Università degli studi di Trieste = University of Trieste, Istituto Nazionale di Fisica Nucleare, Sezione di Trieste (INFN, Sezione di Trieste), Copernicus Astronomical Center of the Polish Academy of Sciences (CAMK), Polish Academy of Sciences (PAN), Laboratoire Univers et Particules de Montpellier (LUPM), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut de Física d’Altes Energies [Barcelone] (IFAE), Universitat Autònoma de Barcelona (UAB), Argonne National Laboratory [Lemont] (ANL), Nagoya University, European Southern Observatory (ESO), US Naval Observatory (US NAVAL OBSERVATORY), US Naval Observatory, Deutsches Elektronen-Synchrotron [Hamburg] (DESY), Princeton University, Universitat de Barcelona, Universitat de Barcelona (UB), Istituto di Astrofisica e Planetologia Spaziali - INAF (IAPS), University of Maryland [College Park], Uniwersytet Jagielloński w Krakowie = Jagiellonian University (UJ), Max-Planck-Institut für Extraterrestrische Physik (MPE), Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), University of California [Berkeley] (UC Berkeley), University College of London [London] (UCL), University of Nevada [Las Vegas] (WGU Nevada), Purdue University [West Lafayette], Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), University of California, U.S. Department of Energy [Washington] (DOE)-UT-Battelle, LLC-Stony Brook University [SUNY] (SBU), State University of New York (SUNY)-State University of New York (SUNY), University of Sofia, Université de Genève (UNIGE), Smithsonian Institution-Harvard University [Cambridge], Consiglio Nazionale delle Ricerche (CNR), 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), University of California [Santa Cruz] (UCSC), 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), Kyoto University [Kyoto], Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), University of Trieste, 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), University of California [Berkeley], Complutense University of Madrid (UCM), National Institute for Nuclear Physics (INFN), Brookhaven National Laboratory [Upton] (BNL), Stony Brook University [SUNY] (SBU), Harvard University [Cambridge]-Smithsonian Institution, Stanford Linear Accelerator Center (SLAC), Stanford University [Stanford], Istituto di Radioastronomia (IRA), Friedrich-Alexander Universitaet Erlangen-Nuernberg, Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM PS1), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Univ. Paris-Sud, Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA) - Grenoble, George Washington University (GW), University of North Florida, Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées (LATT), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-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), Universitat Autònoma de Barcelona [Barcelona] (UAB), and Jagiellonian University [Krakow] (UJ)

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], [PHYS.ASTR.HE]Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a probe class mission concept that will provide essential contributions to multimessenger astrophysics in the late 2020s and beyond. AMEGO combines high sensitivity in the 200 keV to 10 GeV energy range with a wide field of view, good spectral resolution, and polarization sensitivity. Therefore, AMEGO is key in the study of multimessenger astrophysical objects that have unique signatures in the gamma-ray regime, such as neutron star mergers, supernovae, and flaring active galactic nuclei. The order-of-magnitude improvement compared to previous MeV missions also enables discoveries of a wide range of phenomena whose energy output peaks in the relatively unexplored medium-energy gamma-ray band., Comment: Astro2020 APC White Paper Updated to make small change to author list in metadata

19. SPECTRAL AND TEMPORAL PROPERTIES OF THE ULTRA-LUMINOUS X-RAY PULSAR IN M82 FROM 15 YEARS OF CHANDRA OBSERVATIONS AND ANALYSIS OF THE PULSED EMISSION USING NuSTAR.

Author

Murray Brightman, Fiona Harrison, Dominic J. Walton, Felix Fuerst, Ann Hornschemeier, Andreas Zezas, Matteo Bachetti, Brian Grefenstette, Andrew Ptak, Shriharsh Tendulkar, and Mihoko Yukita

Subjects
PULSARS, STELLAR spectra, NEUTRONS spectra, BINARY stars
Abstract

The recent discovery by Bachetti et al. of a pulsar in M82 that can reach luminosities of up to 1040 erg s−1, a factor of ∼100 times the Eddington luminosity for a 1.4 M⊙ compact object, poses a challenge for accretion physics. In order to better understand the nature of this source and its duty cycle, and in light of several physical models that have been subsequently published, we conduct a spectral and temporal analysis of the 0.5–8 keV X-ray emission from this source from 15 years of Chandra observations. We analyze 19 ACIS observations where the point-spread function (PSF) of the pulsar is not contaminated by nearby sources. We fit the Chandra spectra of the pulsar with a power-law model and a disk blackbody model, subjected to interstellar absorption in M82. We carefully assess for the effect of pile-up in our observations, where four observations have a pile-up fraction of >10%, which we account for during spectral modeling with a convolution model. When fitted with a power-law model, the average photon index when the source is at high luminosity (LX > 1039 erg s−1) is Γ = 1.33 ± 0.15. For the disk blackbody model, the average temperature is Tin = 3.24 ± 0.65 keV, the spectral shape being consistent with other luminous X-ray pulsars. We also investigated the inclusion of a soft excess component and spectral break, finding that the spectra are also consistent with these features common to luminous X-ray pulsars. In addition, we present spectral analysis from NuSTAR over the 3–50 keV range where we have isolated the pulsed component. We find that the pulsed emission in this band is best fit by a power-law with a high-energy cutoff, where Γ = 0.6 ± 0.3 and keV. While the pulsar has previously been identified as a transient, we find from our longer-baseline study that it has been remarkably active over the 15-year period, where for 9/19 (47%) observations that we analyzed, the pulsar appears to be emitting at a luminosity in excess of 1039 erg s−1, greater than 10 times its Eddington limit. [ABSTRACT FROM AUTHOR]

Published
2016
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