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Type: Journal article
Title: HESS upper limits on very high energy gamma-ray emission from the microquasar GRS 1915+105
Author: Rowell, G.
Citation: Astronomy and Astrophysics, 2009; 508(3):1135-1140
Publisher: E D P Sciences
Issue Date: 2009
ISSN: 0004-6361
Statement of
HESS Collaboration... F. Acero... G. Rowell... et al.
Abstract: Context: High energy particles reside in the relativistic jets of microquasars, making them possible sources of very high energy radiation (VHE, >100 GeV). Detecting this emission would provide a new handle on jet physics. Aims: Observations of the microquasar GRS 1915+105 with the HESS telescope array were undertaken in 2004–2008 to search for VHE emission. Methods: Stereoscopic imaging of Cherenkov radiation from extensive air showers is used to reconstruct the energy and direction of the incident gamma rays. Results: There is no evidence for a VHE gamma-ray signal either from the direction of themicroquasar or its vicinity. An upper limit of ph cm-2 s-1 (99.9% confidence level) is set on the photon flux above 410 GeV, equivalent to a VHE luminosity of erg s-1 at 11 kpc. Conclusions: The VHE to X-ray luminosity ratio in GRS 1915+105 is at least four orders of magnitude lower than the ratio observed in gamma-ray binaries. The VHE radiative efficiency of the compact jet is less than 0.01% based on its estimated total power of 1038 erg s-1. Particle acceleration in GRS 1915+105 is not efficient at high energies and/or the magnetic field is too strong. It is also possible that VHE gamma-rays are produced by GRS 1915+105, but the emission is highly time-dependent.
Keywords: X-rays: binaries; X-rays: individuals: GRS 1915+105; gamma rays: observations
Rights: © ESO 2009
RMID: 0020094520
DOI: 10.1051/0004-6361/200913389
Appears in Collections:Physics publications

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