Hard X-Ray Emission of the Microquasar GX 339-4 in the Low/Hard State
Abstract
We present the analysis of the high-energy emission of the Galactic black hole binary GX 339-4 in a low/hard state at the beginning of its 2004 outburst. The data from 273 ks of INTEGRAL observations, spread over 4 weeks, are analyzed, along with the existing simultaneous RXTE HEXTE and PCA data. During this period, the flux increases by a factor of ~=3, while the spectral shape is quite unchanged, at least up to 150 keV. The high-energy data allow us to detect the presence of a high-energy cutoff, generally related to thermal mechanisms, and to estimate the plasma parameters in the framework of the Comptonization models. We found an electron temperature of 60-70 keV and an optical depth of around 2.5, with a rather low reflection factor (0.2-0.4). In the last observation, we detected a high-energy excess above 200 keV with respect to thermal Comptonization, while at lower energies the spectrum is practically identical to the previous one taken just 2 days before. This suggests that the low- and high-energy components have a different origin.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2007
- DOI:
- 10.1086/510326
- arXiv:
- arXiv:astro-ph/0611064
- Bibcode:
- 2007ApJ...657..400J
- Keywords:
-
- Accretion;
- Accretion Disks;
- Black Hole Physics;
- Gamma Rays: Observations;
- Stars: Individual: Alphanumeric: GX 330-4;
- X-Rays: Binaries;
- Astrophysics
- E-Print:
- 12 pages, 6 figures, accepted for publication in ApJ