Spectral and Timing Evolution of the Black Hole X-Ray Nova 4U 1543–47 during Its 2002 Outburst

We present an X-ray spectral and timing analysis of 4U 1543-47 during its 2002 outburst based on 49 pointed observations obtained using the Rossi X-Ray Timing Explorer. The outburst reached a peak intensity of 4.2 crab in the 2-12 keV band and declined by a factor of 32 throughout the month-long observation. A 21.9 ± 0.6 mJy radio flare was detected at 1026.75 MHz two days before the X-ray maximum; the radio source was also detected late in the outburst, after the X-ray source entered the "hard" state. The X-ray light curve exhibits the classic shape of a rapid rise and an exponential decay. The spectrum is soft and dominated by emission from the accretion disk. The continuum is fitted with a multicolor disk blackbody (kTmax = 1.04 keV) and a power law (Γ ~ 2.7). Midway through the decay phase, a strong low-frequency quasi-periodic oscillation (ν = 7.3-8.1 Hz) was present for several days. The spectra feature a broad Fe Kα line that is asymmetric, suggesting that the line is due to relativistic broadening rather than Comptonization. Relativistic Laor models provide much better fits to the line than nonrelativistic Gaussian models, particularly near the beginning and end of our observations. The line fits yield estimates for the inner disk radius that are within 6Rg; this result and additional evidence indicates that this black hole may have a nonzero angular momentum.