GRS 1915+105 : High-energy Insights with SPI/INTEGRAL

TL;DR

This study presents two years of high-energy observations of GRS 1915+105, revealing two distinct spectral states with thermal and non-thermal electron populations, independent of the source's temporal variability.

Contribution

First detailed high-energy spectral analysis of GRS 1915+105 using INTEGRAL/SPI data over two years, identifying distinct spectral states and electron populations.

Findings

High-energy spectral states are not correlated with temporal variability.

Spectra are well fitted by thermal Comptonization plus a high-energy powerlaw.

Presence of both thermal and non-thermal electrons confirmed.

Abstract

We report on results of two years of INTEGRAL/SPI monitoring of the Galactic microquasar GRS 1915+105. From September 2004 to May 2006, the source has been observed twenty times with long (approx 100 ks) exposures. We present an analysis of the SPI data and focus on the description of the high-energy (> 20 keV) output of the source. We found that the 20 - 500 keV spectral emission of GRS 1915+105 was bound between two states. It seems that these high-energy states are not correlated with the temporal behavior of the source, suggesting that there is no direct link between the macroscopic characteristics of the coronal plasma and the the variability of the accretion flow. All spectra are well fitted by a thermal comptonization component plus an extra high-energy powerlaw. This confirms the presence of thermal and non-thermal electrons around the black hole.