GRANAT/SIGMA observations of X-ray nova persei 1992
Abstract
We report on the results of the GRANAT/SIGMA observations of the X-ray transient GRO J0422+32 in the 35-1300 keV energy band in 1992-93. In the maximum of the light curve, this black hole candidate was the brightest hard X-ray source detected by SIGMA so far. During the monitoring of the GRO J0422+32 outburst, SIGMA detected a gradual hardening of the source spectrum. In terms of thermal emission of optically thin plasma this hardening corresponds to an increase of the best-fit temperature from ~ 110 keV to ~ 140 keV. Source spectrum is well represented by two component Comptonized disk model /9/. The parameters of the model do not exhibit any statistically significant variation from the average value of (alpha kT_e) of (0.737 +/- 0.01; 25.4 +/- 0.05) for the softer component and (0.39 +/- 0.09; 62.6 +/- 2.4) for the harder (with tau_disk ~ 1.8 for both components). Nevertheless relative normalizations of the two components are changing during our observations by a factor of two. The harder component is fluctuating on a day time-scale and a growth of its contribution to the total flux is accompanied by an increase in the fractorial RMS [0.001-0.1 Hz].
- Publication:
-
Advances in Space Research
- Pub Date:
- May 1997
- DOI:
- 10.1016/S0273-1177(97)00034-3
- Bibcode:
- 1997AdSpR..19...35F