Constraining particle acceleration in Sgr A⋆with simultaneous GRAVITY,Spitzer,NuSTAR, andChandraobservations
Astronomy and Astrophysics, vol. 654, pp. A22
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 theM,K, andHbands in the mid- and near-infrared and in the 2 − 8 keV and 2 − 70 keV bands in the X-ray. The observed spectral slope in the near-infrared band isνLν ∝ ν0.5 ± 0.2; the spectral slope observed in the X-ray band isνLν ∝ ν−0.7 ± 0.5. Using a fast numerical implementation of a synchrotron sphere with a constant radius, magnetic field, and electron density (i.e., a one-zone model), we tested various synchrotron and synchrotron self-Compton 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 synchrotron self-Compton. Two realizations of the one-zone model can explain the observed flare and its temporal correlation: one-zone model in which the near-infrared and X-ray luminosity are produced by synchrotron self-Compton and a model in which the luminosity stems from a cooled synchrotron spectrum. Both models can describe the mean spectral energy distribution (SED) and temporal evolution similarly well. In order to describe the mean SED, both models require specific values of the maximum Lorentz factorγmax, which differ by roughly two orders of magnitude. The synchrotron self-Compton model suggests that electrons are accelerated toγmax ∼ 500, while cooled synchrotron model requires acceleration up toγmax ∼ 5 × 104. The synchrotron self-Compton scenario requires electron densities of 1010cm−3that are much larger than typical ambient densities in the accretion flow. Furthermore, it requires a variation of the particle density that is inconsistent with the average mass-flow rate inferred from polarization measurements and can therefore only be realized in an extraordinary accretion event. In contrast, assuming a source size of 1 RS, 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 factorγmax, implying that sustained particle acceleration is required to explain at least a part of the temporal evolution of the flare.
Authors 83
-
Affiliation as printed
European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
-
University of Lisbon · Instituto Superior Técnico · Centro de Astrofísica e Gravitação
Affiliation as printed
CENTRA – Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal
Universidade de Lisboa – Faculdade de Ciências, Campo Grande, 1749-016 Lisboa, Portugal
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Massachusetts Institute of Technology
Affiliation as printed
MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA 02139, USA
-
Centre National de la Recherche Scientifique · European Southern Observatory · Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes
Affiliation as printed
European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
-
Trottier Space Institute at McGill · McGill University
Affiliation as printed
Department of Physics, McGill University, 3600 University St., Montreal, QC H3A 2T8, Canada
McGill Space Institute, 3550 University St., Montreal, QC H3A 2A7, Canada
-
Affiliation as printed
European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
-
Max Planck Institute for Astronomy
Affiliation as printed
Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
-
Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
Affiliation as printed
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 Place Jules Janssen, 92195 Meudon, France
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Leiden University · Max Planck Institute for Extraterrestrial Physics · Leiden Observatory
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
Sterrewacht Leiden, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands
-
Joint Institute for Laboratory Astrophysics · University of Colorado Boulder · Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Department of Astrophysical & Planetary Sciences, JILA, University of Colorado, Duane Physics Bldg., 2000 Colorado Ave, Boulder, CO 80309, USA
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Max Planck Institute for Extraterrestrial Physics · Technical University of Munich
Affiliation as printed
Department of Physics, Technical University Munich, James-Franck-Strasse 1, 85748 Garching, Germany
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
University of Cologne · Max Planck Institute for Radio Astronomy
Affiliation as printed
1st Institute of Physics, University of Cologne, Zülpicher Strasse 77, 50937 Cologne, Germany
Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, 53121 Bonn, Germany
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Center for Astrophysics Harvard & Smithsonian
Affiliation as printed
Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
California Institute of Technology
Affiliation as printed
Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
-
University of Illinois Urbana-Champaign
Affiliation as printed
Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801, USA
-
University of Lisbon · Universidade do Porto · Instituto Superior Técnico · Centro de Astrofísica e Gravitação
Affiliation as printed
CENTRA – Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal
Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
Affiliation as printed
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 Place Jules Janssen, 92195 Meudon, France
-
Max Planck Institute for Extraterrestrial Physics · University of California, Berkeley
Affiliation as printed
Departments of Physics and Astronomy, Le Conte Hall, University of California, Berkeley, CA 94720, USA
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Center for Astrophysics Harvard & Smithsonian
Affiliation as printed
Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Trottier Space Institute at McGill · McGill University
Affiliation as printed
Department of Physics, McGill University, 3600 University St., Montreal, QC H3A 2T8, Canada
McGill Space Institute, 3550 University St., Montreal, QC H3A 2A7, Canada
-
Affiliation as printed
Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, Room 1027, New York, NY 10027, USA
-
California Institute of Technology
Affiliation as printed
Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
-
Affiliation as printed
European Southern Observatory, Casilla, 19001 Santiago 19, Chile
-
Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
Affiliation as printed
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 Place Jules Janssen, 92195 Meudon, France
-
Max Planck Institute for Astronomy
Affiliation as printed
Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
-
Max Planck Institute for Astronomy
Affiliation as printed
Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
-
Center for Astrophysics Harvard & Smithsonian
Affiliation as printed
Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
-
Affiliation as printed
1st Institute of Physics, University of Cologne, Zülpicher Strasse 77, 50937 Cologne, Germany
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Affiliation as printed
European Southern Observatory, Casilla, 19001 Santiago 19, Chile
-
Centre National de la Recherche Scientifique · Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes
Affiliation as printed
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
-
Affiliation as printed
European Southern Observatory, Casilla, 19001 Santiago 19, Chile
-
Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
Affiliation as printed
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 Place Jules Janssen, 92195 Meudon, France
-
Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
Affiliation as printed
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 Place Jules Janssen, 92195 Meudon, France
-
Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
Affiliation as printed
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 Place Jules Janssen, 92195 Meudon, France
-
Centre National de la Recherche Scientifique · Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes
Affiliation as printed
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
-
Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
Affiliation as printed
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 Place Jules Janssen, 92195 Meudon, France
-
California Institute of Technology
Affiliation as printed
Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125, USA
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Affiliation as printed
Anton Pannekoek Institute for Astronomy, University of Amsterdam, 1098 XH Amsterdam, The Netherlands
-
Affiliation as printed
Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, Room 1027, New York, NY 10027, USA
-
University of California, Los Angeles
Affiliation as printed
UCLA Galactic Center Group, Physics and Astronomy Department, University of California, Los Angeles, CA 90024, USA
-
Affiliation as printed
Villanova University, Department of Physics, Villanova, PA 19085, USA
-
Centre National de la Recherche Scientifique · University of Cambridge · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
Affiliation as printed
Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 Place Jules Janssen, 92195 Meudon, France
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
Affiliation as printed
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 Place Jules Janssen, 92195 Meudon, France
-
Centre National de la Recherche Scientifique · Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes
Affiliation as printed
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
-
Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
Affiliation as printed
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 Place Jules Janssen, 92195 Meudon, France
-
Joint Institute for Laboratory Astrophysics · University of Colorado Boulder · Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Department of Astrophysical & Planetary Sciences, JILA, University of Colorado, Duane Physics Bldg., 2000 Colorado Ave, Boulder, CO 80309, USA
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
European Southern Observatory · Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
Affiliation as printed
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 Place Jules Janssen, 92195 Meudon, France
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Max Planck Institute for Astronomy
Affiliation as printed
Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
-
Center for Astrophysics Harvard & Smithsonian
Affiliation as printed
Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
California Institute of Technology · Jet Propulsion Laboratory
Affiliation as printed
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, MS 169-224, Pasadena, CA 91109, USA
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Affiliation as printed
1st Institute of Physics, University of Cologne, Zülpicher Strasse 77, 50937 Cologne, Germany
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
Affiliation as printed
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 Place Jules Janssen, 92195 Meudon, France
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Max Planck Institute for Extraterrestrial Physics · Weizmann Institute of Science
Affiliation as printed
Department of Particle Physics & Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Center for Astrophysics Harvard & Smithsonian
Affiliation as printed
Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
-
Max Planck Institute for Radio Astronomy
Affiliation as printed
Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, 53121 Bonn, Germany
-
Affiliation as printed
European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
-
University of Cologne · Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
1st Institute of Physics, University of Cologne, Zülpicher Strasse 77, 50937 Cologne, Germany
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
-
Affiliation as printed
Bard College Physics Program, 30 Campus Road, Annandale-On-Hudson, NY 12504, USA
-
Affiliation as printed
European Southern Observatory, Casilla, 19001 Santiago 19, Chile
Cited by 65 stored of 65
No patents citing this paper on Lens.org (checked 2026-10-11).