Hauke Worpel, Duncan K. Galloway, Daniel J. Price
The standard approach for time-resolved X-ray spectral analysis of thermonuclear bursts involves subtraction of the pre-burst emission as background. This approach implicitly assumes that the accretion rate (which determines the persistent flux) remains constant throughout the burst, despite the strongly time-dependent radiation flux onto the accreting material. We reanalyzed 332 bright bursts observed from 40 sources by {\it RXTE}, introducing a factor $f_a$ by which the persistent emission is multiplied, as a variable parameter in our spectral fits. We found that for the majority of spectra the best-fit value of $f_a$ is significantly greater than 1, suggesting that the persistent emission increases during a burst. An inverse correlation with the pre-burst accretion rate is found, consistent with theoretical models of the disc response. We suggest that this modified approach may provide more accurate burst spectral parameters, as well as offering a probe of the accretion disk structure.
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http://arxiv.org/abs/1303.4824
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