X-Ray Observations of the Black Hole Transient 4U 1630-47 During Two Years of X-Ray Activity

Abstract

The black hole candidate (BHC) X-ray transient 4U 1630-47 continuously produced strong X-ray emission for over 2 years during 2002-2004. We use observations made with the Rossi X-ray Timing Explorer (RXTE) to study the source throughout the outburst along with hard X-ray images from the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL). The source exhibits extreme behaviors, including measured inner disk temperatures (Tin) between 2.7 and 3.8 keV, which are only rivaled by the brightest BHC systems. If the high temperatures are caused by the dominance of electron scattering opacity in the inner regions of the accretion disk, a luminosity >20% of the Eddington limit is theoretically required. We detect several types of variability, including hard 10-100 s flares at the highest disk luminosities in a regime where the source deviates from the Ldisk/Tin relationship that is seen at lower luminosities, possibly suggesting that we are seeing transitions between a standard disk and a "slim" disk. The X-ray properties in 2002-2004 are significantly different from those seen during the 1998 outburst, which is the only outburst with detected radio jet emission. Our results support the "jet-line" concept recently advanced by Fender and co-workers. Our study allows for a test of the quantitative McClintock & Remillard spectral state definitions. We also report on detections of the nearby sources IGR J16320-4751 and IGR J16358-4726.