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Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - Experimentelle Elementarteilchenphysik

Humboldt-Universität zu Berlin | Mathematisch-Naturwissen­schaft­liche Fakultät | Institut für Physik | Experimentelle Elementarteilchenphysik | H.E.S.S. | Talks & Papers | HESS upper limits on very high energy gamma-ray emission from the microquasar GRS 1915+105

The H Collaboration (2009)

HESS upper limits on very high energy gamma-ray emission from the microquasar GRS 1915+105

aap, 508:1135-1140.

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 the microquasar or its vicinity. An upper limit of 6.1× 10^-13 ph cm^-2 s^-1 (99.9% confidence level) is set on the photon flux above 410 GeV, equivalent to a VHE luminosity of ˜ 10^34 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 10^38 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. Supported by CAPES Foundation, Ministry of Education of Brazil.

Provided by the SAO/NASA Astrophysics Data System