Class transition during the 2008 outburst of 4U 1630-47

Abstract

The class transitions of light curves from soft class (high count) to hard class (low count) or vice versa of the Black Hole Candidate (BHC) X-ray transient source 4U 1630-47 were observed during the 2008 outburst. The detailed spectral and timing analysis of the X-ray data of the source obtained from Rossi X-ray Timing Explorer (RXTE) were carried out. It was found that the variation of the flux and inner disk temperature with Modified Julian Day (MJD) followed almost same nature. When flux of the object increased, inner disk temperature also increased. Mean photon count rates in the light curves were seen to change before, after and during the outburst. We observed that during class transitions the slopes of the power density spectra (PDS) changed but it remained same when there was no transition. It was also observed that PDS of soft class became steeper than that of the hard class. The variation in the accretion rates, which was thought to be the sole cause of the class-to-class variation, must be nearly freely falling like other compact objects such as GRS 1915 + 105, Cygnus X-I and Cygnus X-3.