Simultaneous H.E.S.S. and Chandra observations of Sagittarius A* during an X-ray flare

F. Aharonian , A.G. Akhperjanian , U. Barres de Almeida , A.R. Bazer-Bachi (1) , Y. Becherini (2) , B. Behera , W. Benbow , K. Bernlöhr , C. Boisson (3) , A. Bochow , V. Borrel (1) , I. Braun , E. Brion (4) , J. Brucker , P. Brun (4) , R. Bühler , T. Bulik , I. Büsching , T. Boutelier (5) , S. Carrigan , P.M. Chadwick , A. Charbonnier (6) , R.C.G. Chaves , A. Cheesebrough , L.-M. Chounet (7) , A.C. Clapson , G. Coignet (8) , B. Degrange (7) , C. Deil , H.J. Dickinson , A. Djannati-Ataï (9) , W. Domainko , L.O'C. Drury , F. Dubois (8) , G. Dubus (5) , J. Dyks , M. Dyrda , K. Egberts , D. Emmanoulopoulos , P. Espigat (2) , C. Farnier (10) , F. Feinstein (10) , A. Fiasson (10) , A. Förster , G. Fontaine (7) , M. Füsling , S. Gabici , Y.A. Gallant (10) , L. Gérard (2) , B. Giebels (7) , J.F. Glicenstein (4) , B. Glück , P. Goret (4) , C. Hadjichristidis , D. Hauser , M. Hauser , S. Heinz , G. Heinzelmann , G. Henri (5) , G. Hermann , J.A. Hinton , A. Hoffmann , W. Hofmann , M. Holleran , S. Hoppe , D. Horns , A. Jacholkowska (6) , O.C. de Jager , I. Jung , K. Katarzy'Nski , S. Kaufmann , E. Kendziorra , M. Kerschhaggl , D. Khangulyan , B. Khélifi (7) , D. Keogh , Nu. Komin (4) , K. Kosack , G. Lamanna (8) , J.-P. Lenain (3) , T. Lohse , V. Marandon (2) , J.M. Martin (3) , O. Martineau-Huynh (6) , A. Marcowith (10) , D. Maurin (6) , T.J.L. Mccomb , M.C. Medina (3) , R. Moderski , Emmanuel Moulin (4) , M. Naumann-Godo (7) , M. de Naurois (6) , D. Nedbal , D. Nekrassov , J. Niemiec , S.J. Nolan , S. Ohm , J.-F. Olive (1) , E. de Oña Wilhelmi (2) , K.J. Orford , J.L. Osborne , M. Ostrowski , M. Panter , G. Pedaletti , G. Pelletier (5) , P.-O. Petrucci (5) , S. Pita (2) , G. Pühlhofer , M. Punch (2) , A. Quirrenbach , B.C. Raubenheimer , M. Raue , S.M. Rayner , M. Renaud , F. Rieger , J. Ripken , L. Rob , S. Rosier-Lees (8) , G. Rowell , B. Rudak , C.B. Rulten , J. Ruppel , V. Sahakian , A. Santangelo , R. Schlickeiser , F.M. Schöck , R. Schröder , U. Schwanke , S. Schwarzburg , S. Schwemmer , A. Shalchi , J.L. Skilton , H. Sol (3) , D. Spangler , L. Stawarz , R. Steenkamp , C. Stegmann , G. Superina (7) , P.H. Tam , J.-P. Tavernet (6) , R. Terrier (2) , O. Tibolla , C. van Eldik , G. Vasileiadis (10) , C. Venter , J.P. Vialle (8) , P. Vincent (6) , M. Vivier (4) , H.J. Völk , F. Volpe (7) , S.J. Wagner , M. Ward , A.A. Zdziarski , A. Zech (3)

1 CESR - Centre d'étude spatiale des rayonnements
2 APC (UMR_7164) - AstroParticule et Cosmologie
3 LUTH (UMR_8102) - Laboratoire Univers et Théories
4 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
5 LAOG - Laboratoire d'Astrophysique de Grenoble
6 LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
7 LLR - Laboratoire Leprince-Ringuet
8 LAPP - Laboratoire d'Annecy de Physique des Particules
9 APC - AHE - APC - Astrophysique des Hautes Energies
10 LPTA - Laboratoire de Physique Théorique et Astroparticules

The rapidly varying (~10 minute timescale) non-thermal X-ray emission observed from Sgr A* implies that particle acceleration is occuring close to the event horizon of the supermassive black hole. The TeV gamma-ray source HESS J1745-290 is coincident with Sgr A* and may be closely related to its X-ray emission. Simultaneous X-ray and TeV observations are required to elucidate the relationship between these objects. We report on joint H.E.S.S./Chandra observations performed in July 2005, during which an X-ray flare was detected. Despite a factor of 9 increase in the X-ray flux of Sgr A*, no evidence is found for an increase in the TeV gamma-ray flux from this region. We find that an increase in the gamma-ray flux of a factor of 2 or greater can be excluded at a confidence level of 99%. This finding disfavours scenarios in which the keV and TeV emission are associated with the same population of accelerated particles and in which the bulk of the gamma-ray emission is produced within ~10^{14} cm (~100 R_S) of the supermassive black hole.

Mots clés: X-rays:individual sources:Sgr A; gamma-rays:observations

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Cosmologie et astrophysique extra-galactique [astro-ph.CO]

F. Aharonian, A.G. Akhperjanian, U. Barres de Almeida, A.R. Bazer-Bachi, Y. Becherini, et al.. Simultaneous H.E.S.S. and Chandra observations of Sagittarius A* during an X-ray flare. Astronomy and Astrophysics - A&A, 2008, 492, pp.L25-L28. ⟨10.1051/0004-6361:200810912⟩. ⟨in2p3-00348809⟩