1. Constraining particle acceleration in Sgr A⋆ with simultaneous GRAVITY, Spitzer, NuSTAR, and Chandra observations
- Author
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Wolfgang Brandner, A. Jiménez-Rosales, Mark Gurwell, Stefan Hippler, Christian Straubmeier, Th. Henning, Fiona A. Harrison, Jason Dexter, N. M. Förster Schreiber, F. Vincent, Pierre Kervella, Daryl Haggard, S. Yazici, Silvia Scheithauer, Oliver Pfuhl, Y. Dallilar, T. Taro Shimizu, Idel Waisberg, Odele Straub, K. Foster, Felix Widmann, Sera Markoff, Dieter Lutz, J.-B. Le Bouquin, M. Bauböck, Matthew Horrobin, Yann Clénet, P. T. de Zeeuw, Gabriele Ghisellini, Howard A. Smith, Frederick K. Baganoff, Daniel Stern, Thibaut Paumard, Eckhard Sturm, Ric Davies, M. Nowak, Andreas Eckart, Andreas Kaufer, Sebastian Rabien, Laurent Jocou, Paulo J. V. Garcia, Ekkehard Wieprecht, Reinhard Genzel, Jinyi Shangguan, G. Rodríguez-Coira, Patrick Lowrance, C. J. Hailey, Thomas Ott, S. Zhang, A. Drescher, G. Ponti, Giovanni G. Fazio, Steven P. Willner, S. D. von Fellenberg, Linda J. Tacconi, Maryam Habibi, H. Bonnet, Julien Woillez, V. Lapeyrère, Sylvestre Lacour, António Amorim, Erich Wiezorrek, Xavier Haubois, Guy Perrin, J. Neilsen, K. Mori, Eric Gendron, Frank Eisenhauer, G. Heißel, Pierre Léna, Joseph L. Hora, Karine Perraut, Charles F. Gammie, Feng Gao, G. Witzel, Gérard Zins, Mark Morris, André Young, Julia Stadler, Jean-Phillipe Berger, Hope Boyce, Stefan Gillessen, Lieselotte Jochum, Roberto Abuter, High Energy Astrophys. & Astropart. Phys (API, FNWI), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
- Subjects
Accretion ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Astrophysics ,Electron ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Astrophysics - high energy astrophysical phenomena ,law.invention ,Luminosity ,symbols.namesake ,law ,0103 physical sciences ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Accretion (meteorology) ,Galaxy: center ,010308 nuclear & particles physics ,[SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE] ,Astronomy and Astrophysics ,Black hole physics ,Synchrotron ,ddc ,Particle acceleration ,Lorentz factor ,13. Climate action ,Space and Planetary Science ,Accretion disks ,symbols ,Spectral energy distribution ,Flare - Abstract
We report the time-resolved spectral analysis of a bright near-infrared and moderate X-ray flare of Sgr A*. We obtained light curves in the $M$-, $K$-, and $H$-bands in the mid- and near-infrared and in the $2-8~\mathrm{keV}$ and $2-70~\mathrm{keV}$ bands in the X-ray. The observed spectral slope in the near-infrared band is $\nu L_\nu\propto \nu^{0.5\pm0.2}$; the spectral slope observed in the X-ray band is $\nu L_\nu \propto \nu^{-0.7\pm0.5}$. We tested synchrotron and synchrotron self-Compton (SSC) scenarios. The observed near-infrared brightness and X-ray faintness, together with the observed spectral slopes, pose challenges for all models explored. We rule out a scenario in which the near-infrared emission is synchrotron emission and the X-ray emission is SSC. A one-zone model in which both the near-infrared and X-ray luminosity are produced by SSC and a model in which the luminosity stems from a cooled synchrotron spectrum can explain the flare. In order to describe the mean SED, both models require specific values of the maximum Lorentz factor $\gamma_{max}$, which however differ by roughly two orders of magnitude: the SSC model suggests that electrons are accelerated to $\gamma_{max}\sim 500$, while cooled synchrotron model requires acceleration up to $\gamma_{max}\sim5\times 10^{4}$. The SSC scenario requires electron densities of $10^{10}~\mathrm{cm^{-3}}$ much larger than typical ambient densities in the accretion flow, and thus require in an extraordinary accretion event. In contrast, assuming a source size of $1R_s$, the cooled synchrotron scenario can be realized with densities and magnetic fields comparable with the ambient accretion flow. For both models, the temporal evolution is regulated through the maximum acceleration factor $\gamma_{max}$, implying that sustained particle acceleration is required to explain at least a part of the temporal evolution of the flare., Comment: accepted for publication in Astronomy & Astrophysics; preview abstract shortened due to arXiv requirements
- Published
- 2021
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