Abuter, R., Amorim, A., Bauboeck, M., Baganoff, F., Berger, J. P., Boyce, H., Bonnet, H., Brandner, W., Clenet, Y., Davies, R., de Zeeuw, P. T., Dexter, J., Dallilar, Y., Drescher, A., Eckart, A., Eisenhauer, F., Fazio, G. G., Schreiber, N. M. Foerster, Foster, K., Gammie, C., Garcia, P., Gao, F., Gendron, E., Genzel, R., Ghisellini, G., Gillessen, S., Gurwell, M. A., Habibi, M., Haggard, D., Hailey, C., Harrison, F. A., Haubois, X., Heissel, G., Henning, T., Hippler, S., Hora, J. L., Horrobin, M., Jimenez-Rosales, A., Jochum, L., Jocou, L., Kaufer, A., Kervella, P., Lacour, S., Lapeyrere, V, Le Bouquin, J-B, Lena, P., Lowrance, P. J., Lutz, D., Markoff, S., Mori, K., Morris, M. R., Neilsen, J., Nowak, M., Ott, T., Paumard, T., Perraut, K., Perrin, G., Ponti, G., Pfuhl, O., Rabien, S., Rodriguez-Coira, G., Shangguan, J., Shimizu, T., Scheithauer, S., Smith, H. A., Stadler, J., Stern, D. K., Straub, O., Straubmeier, C., Sturm, E., Tacconi, L. J., Vincent, F., von Fellenberg, S., Waisberg, I, Widmann, F., Wieprecht, E., Wiezorrek, E., Willner, S. P., Witzel, G., Woillez, J., Yazici, S., Young, A., Zhang, S. and Zins, G. (2021). Constraining particle acceleration in Sgr A(*) with simultaneous GRAVITY, Spitzer, NuSTAR, and Chandra observations. Astron. Astrophys., 654. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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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 keV and 2 - 70 keV bands in the X-ray. The observed spectral slope in the near-infrared band is nu L-nu proportional to proportional to nu(0.5 +/- 0.2); the spectral slope observed in the X-ray band is nu L-nu proportional to nu(-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 factor gamma(max), which differ by roughly two orders of magnitude. The synchrotron self-Compton model suggests that electrons are accelerated to gamma(max)similar to 500, while cooled synchrotron model requires acceleration up to gamma(max)similar to 5 x 10(4). The synchrotron self-Compton scenario requires electron densities of 10(10) cm(-3) that 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 R-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.

Item Type: Journal Article
Creators:
CreatorsEmailORCIDORCID Put Code
Abuter, R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Amorim, A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Bauboeck, M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Baganoff, F.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Berger, J. P.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Boyce, H.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Bonnet, H.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Brandner, W.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Clenet, Y.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Davies, R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
de Zeeuw, P. T.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Dexter, J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Dallilar, Y.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Drescher, A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Eckart, A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Eisenhauer, F.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Fazio, G. G.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Schreiber, N. M. FoersterUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Foster, K.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Gammie, C.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Garcia, P.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Gao, F.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Gendron, E.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Genzel, R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Ghisellini, G.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Gillessen, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Gurwell, M. A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Habibi, M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Haggard, D.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Hailey, C.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Harrison, F. A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Haubois, X.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Heissel, G.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Henning, T.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Hippler, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Hora, J. L.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Horrobin, M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Jimenez-Rosales, A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Jochum, L.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Jocou, L.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Kaufer, A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Kervella, P.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Lacour, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Lapeyrere, VUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Le Bouquin, J-BUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Lena, P.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Lowrance, P. J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Lutz, D.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Markoff, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Mori, K.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Morris, M. R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Neilsen, J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Nowak, M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Ott, T.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Paumard, T.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Perraut, K.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Perrin, G.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Ponti, G.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Pfuhl, O.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Rabien, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Rodriguez-Coira, G.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Shangguan, J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Shimizu, T.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Scheithauer, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Smith, H. A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Stadler, J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Stern, D. K.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Straub, O.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Straubmeier, C.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Sturm, E.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Tacconi, L. J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Vincent, F.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
von Fellenberg, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Waisberg, IUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Widmann, F.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Wieprecht, E.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Wiezorrek, E.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Willner, S. P.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Witzel, G.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Woillez, J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Yazici, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Young, A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Zhang, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Zins, G.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
URN: urn:nbn:de:hbz:38-607198
DOI: 10.1051/0004-6361/202140981
Journal or Publication Title: Astron. Astrophys.
Volume: 654
Date: 2021
Publisher: EDP SCIENCES S A
Place of Publication: LES ULIS CEDEX A
ISSN: 1432-0746
Language: English
Faculty: Unspecified
Divisions: Unspecified
Subjects: no entry
Uncontrolled Keywords:
KeywordsLanguage
SAGITTARIUS-A-ASTERISK; SUPERMASSIVE BLACK-HOLE; X-RAY FLARE; NEAR-INFRARED FLARES; GALACTIC-CENTER; XMM-NEWTON; RAPID VARIABILITY; GRMHD SIMULATIONS; SPECTRAL INDEX; EMISSIONMultiple languages
Astronomy & AstrophysicsMultiple languages
URI: http://kups.ub.uni-koeln.de/id/eprint/60719

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