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

Abstract

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.

5 pages, 2 figures

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• Concurrent X-ray, near-infrared, sub-millimeter, and GeV gamma-ray observations of Sgr A*
• The X-ray flaring properties of Sgr A* during six years of monitoring with Swift
• The Fermi All-sky Variability Analysis: A list of flaring gamma-ray sources and the search for transients in our Galaxy
• Statistics of X-ray flares of Sagittarius A*: evidence for solar-like self-organized criticality phenomenon
• Gamma rays from the Galactic Centre region: a review
• A magnetohydrodynamic model for multi-wavelength flares from Sagittarius~A${}^{\star }$ (I): model and the near-infrared and X-ray flares
• VHE Emission from Magnetic Reconnection in the RIAF of SgrA*
• A Leptonic Model of Steady High-Energy Gamma-Ray Emission from Sgr A${}^{\ast }$
• Hybrid model of GeV-TeV gamma ray emission from Galactic Center
• Soft gamma-ray constraints on a bright flare from the Galactic Center supermassive black hole
• A decade of dark matter searches with ground-based Cherenkov telescopes
• Exploring the Nature of the Galactic Center Gamma-Ray Source with the Cherenkov Telescope Array
• The Galactic Center: A PeV Cosmic Ray Acceleration Factory
• Modelling the time dependence of the TeV Gamma-ray source at the Galactic Centre
• Locating the VHE source in the Galactic Centre with milli-arcsecond accuracy
• H.E.S.S.: The High Energy Stereoscopic System
• High Energy Emission from the Galactic Center
• Search for long-term variability of HESS J1745-290