A ROSAT observation of the black hole candidate GRO J0422+32.
Abstract
We report on a ROSAT HRI observation of the hard transient GRO J0422+32 about 42 days after the start of the outburst. The X-ray position (error radius 6 arcsec) agrees well with the positions of the proposed optical and radio counterparts. In the ROSAT energy band (0.1-2.4 keV) the source showed strong flaring activity; a power spectrum analysis of the photon arrival times yields a spectrum with a decrease at frequencies above 0.1 Hz that can be described by a power law with a slope of -1.5. Below 0.1 Hz the spectrum flattens; QPO peaks reported in hard X-rays are confirmed. The integrated rms variability is very high (∼4O%). The measured 0.1-2.4 keV X-ray flux of 0.3 Crab does not require an additional soft X-ray component in GRO J0422+32, if the source followed the decay trend reported in hard X-rays. The flaring activity and X-ray spectrum of GRO J0422+32 are similar to other black hole candidates in their "hard" spectral state.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 1993
- Bibcode:
- 1993A&A...273L..11P
- Keywords:
-
- X-rays: stars;
- Accretion;
- accretion disks;
- Black hole physics