4U 1630-47 Enters a Bright X-Ray Flaring State
ATel #161; John A. Tomsick (UC San Diego)
on 27 May 2003; 16:59 UT
Credential Certification: John A. Tomsick (jtomsick@ucsd.edu)
Subjects: X-ray, Black Hole, Transient
The black hole candidate X-ray transient 4U 1630-47 is currently undergoing an extended outburst that began in 2002 September (see ATELs #106, #108, and #109) and has now persisted for nearly 260 days. Over the past 10 days (MJD 52,776-52,786), the source brightened from 20 c/s to over 40 c/s in the Rossi X-ray Timing Explorer ASM, and the 1.5-12 keV flux is currently near 2E-8 erg cm^-2 s^-1. As the flux increased, our RXTE/PCA observations indicate that the X-ray (3-60 keV) variability on ~10-100 second time scales increased significantly. On 2003 May 18 and May 21, the source exhibited multiple 50-100 second X-ray flares, during which the flux increased by a factor of 1.5-2.0. These flares appear to be similar to the flares seen near the start of the outburst (see ATEL #109 by Homan & Wijnands). A detailed analysis of the May 21 (MJD 52,780.7) PCA observation indicates that the other X-ray spectral and timing properties are similar to the properties at the start of the outburst. The energy spectrum is well-described by a disk-blackbody with a inner disk temperature
of 1.6 keV plus a power-law with a photon index of 2.4. The power spectrum has a power-law shape with a fractional rms of 12% (0.01-100 Hz), and no QPOs are present.
