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D.K. Galloway (MIT), M.P. Muno (UCLA), D. Chakrabarty (MIT), D. Psaltis (U. Arizona), J.M. Hartman (MIT)
We have assembled a sample of 912 thermonuclear X-ray bursts from public observations of 43 sources by the Rossi X-ray Timing Explorer. We have undertaken time-resolved spectral fitting of the burst emission in order to measure peak burst fluxes, burst fluence, and the characteristic evolution time-scales of the burst flux. We have also fitted the persistent flux for each observation of the bursting sources, and searched for burst oscillations at the known oscillation frequencies in 13 sources.
We have found that in general the peak flux of photospheric radius-expansion bursts from individual sources is not consistent, and exhibits a fractional standard deviation of 14% in the mean. We have combined bursts from various subsets of the burst sources to investigate the variation of the burst rate, energetics, and timescale as a function of accretion rate. We have also made a detailed study of bursts with very short (\la30~min recurrence times, and we find evidence for two distinct populations of such bursts. We describe the bursts observed from 5 new burst sources discovered by RXTE, as well as two new transient outbursts of previously known sources. Finally, we summarise the frequency of detection of burst oscillations in those sources known to exhibit them and describe the dependence of the presence of oscillations on the properties of the bursts.
This work was supported in part by the NASA Long Term Space Astrophysics program under grant NAG 5-9184.
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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.