# Oral Presentation Astronomical Society of Australia Annual Scientific Meeting including HWWS 2013

#### Evidence for accretion rate change during type I X-ray bursts (#94)

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1. MoCA, Clayton, VIC, Australia

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 persistent flux remains constant throughout the burst. We reanalyzed 332 photospheric radius expansion 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 typically increases during a burst. While PRE bursts were selected, the $f_a$ variation is not confined to the radius expansion period of the burst. Our modified model improves the spectral fits but does not yet give perfect $\chi^2$. We interpret elevated $f_a$ as an increase of accretion rate onto the neutron star. An inverse correlation of $f_a$ with the persistent flux 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.