We report the discovery of an anti-correlation between the soft and the hard X-ray lightcurves of the X-ray binary Aql X-1 when bursting. This behavior may indicate that the corona is cooled by the soft X-ray shower fed by the type-I X-ray bursts, and that this process happens within a few seconds. Stacking the Aql X-1 lightcurves of type-I bursts, we find a shortage in the 40--50 keV band, delayed by 4.5±1.4 s with respect to the soft X-rays. The photospheric radius expansion (PRE) bursts are different in that neither a shortage nor an excess shows up in the hard X-ray lightcurve.
@article{arxiv.1309.6380,
title = {The hard X-ray behavior of Aql X-1 during type-I bursts},
author = {Yu-Peng Chen and Shu Zhang and Shuang-Nan Zhang and Long Ji and Diego F. Torres and Peter Kretschmar and Jian Li and Jian-Min Wang},
journal= {arXiv preprint arXiv:1309.6380},
year = {2015}
}