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E. Kalemci, J.A. Tomsick, R. Rothschild (Center for Astrophysics and Space Science, University of California, San Diego)
We will present broadband timing studies of the black hole candidate X-ray transient XTE J1550-564 focusing on the low frequency (0.1-6 Hz) quasi-periodic oscillations. Although these QPOs have been extensively studied in the 2-15 keV energy band, their origins are not well-understood. We have devised a method to correct for the deadtime effects in RXTE/HEXTE power spectra, allowing us to constrain the QPO properties at energies up to 120 keV. For some observations, we report 60-120 keV QPO detections, and useful upper limits on the strength of the QPO in this energy band are obtained in other cases. Our results indicate some evolution in the QPO properties with frequency. For example, the strength of the QPO in the 60-120 keV energy band is higher in the 0.2-2.0 Hz frequency range than it is for QPOs above 2 Hz. These studies may lead to an improved understanding of QPO production and may have important implications for constraining accretion geometries and determining the temperature profile of the corona.
The author(s) of this abstract have provided an email address for comments about the abstract: emrahk@mamacass.ucsd.edu