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E. Kalemci, J. A. Tomsick, R. E. Rothschild (CASS / UCSD), K. Pottschmidt (IAAT), P. Kaaret (Harvard-Smithsonian CfA)
We analyzed RXTE power spectra of the black hole candidate (BHC) XTE J1550-564 during its transition to the hard state in the decay of the 2000 outburst. We detected a high frequency QPO at 72 Hz in one observation with an rms amplitude of 4.1%. This frequency is lower than the 102-284 Hz QPOs that have been seen before for this source, and this may be related to changes in the system that occur during outburst decay. We found a low frequency QPO that changes from 4.1 to 0.36 Hz during the decay. An excellent correlation between the QPO frequency and the break frequency of the continuum is observed. The power spectra also showed rich aperiodic variability at both low and high frequencies. In this paper, we compare these timing properties with those previously observed for XTE J1550-564 and other BHCs and discuss the implications for QPO models and black hole accretion.
The author(s) of this abstract have provided an email address for comments about the abstract: emrahk@mamacass.ucsd.edu