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arXiv · 2207.04107

Burst-Disk Interaction in 4U 1636-536 as observed by NICER

Tolga Guver·Funda Bostanci·Tugba Boztepe·Ersin Gogus·Peter Bult·Unnati Kashyap·Manoneeta Chakraborty·David R. Ballantyne·Renee Ludlam·Christian Malacaria·Gaurava K. Jaisawal·Tod E. Strohmayer·Sebastien Guillot
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Abstract

We present the detection of 51 thermonuclear X-ray bursts observed from 4U 1636-536 by the Neutron Star Interior Composition Explorer (NICER) over the course of a three year monitoring campaign. We performed time resolved spectroscopy for 40 of these bursts and showed the existence of a strong soft excess in all the burst spectra. The excess emission can be characterized by the use of a scaling factor (f_a method) to the persistent emission of the source, which is attributed to the increased mass accretion rate on to the neutron star due to Poynting-Robertson drag. The soft excess emission can also be characterized by the use of a model taking into account the reflection of the burst emission off of the accretion disk. We also present time resolved spectral analysis of 5 X-ray bursts simultaneously observed by NICER and AstroSat, which confirm the main results with even greater precision. Finally, we present evidence for Compton cooling using 7 X-ray bursts observed contemporaneously with \nustar, by means of a correlated decrease in the hard X-ray lightcurve of 4U 1636-536 as the bursts start.

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Tolga Guver, Funda Bostanci, Tugba Boztepe, Ersin Gogus, Peter Bult, Unnati Kashyap, Manoneeta Chakraborty, David R. Ballantyne, Renee Ludlam, Christian Malacaria, Gaurava K. Jaisawal, Tod E. Strohmayer, Sebastien Guillot. 2022-07-08. Burst-Disk Interaction in 4U 1636-536 as observed by NICER. https://doi.org/10.3847/1538-4357%2Fac8106

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