Flaring events in Ultraluminous X-ray sources
Abstract
Ultraluminous X-ray sources (ULXs) are the brightest X-ray binaries, luminosity of which exceed the Eddington limit of a ten solar mass black hole. Unique spectral curvature around 6-10 keV manifests that the sources have a distinctive accretion process compared to the sub-Eddington X-ray binary accretors. Modern understanding interprets that most ULXs are stellar-mass super-Eddington accretors, few of them being confirmed to host Neutron stars. Interesting transient phenomena in ULXs are short-term flaring events that have been seen in a few sources intermittently. These flaring activities are crucial to understanding the accretion state transitions in these sources. We will discuss the detection of flaring events in a nearby ultraluminous X-ray source, NGC 4395 ULX1, using XMM-NEWTON observations. Harder photons dominate the flaring events compared to the steady emission periods. This is also evident from the higher fractional variability in the high energy regime. The flaring spectra are related to higher slim disk temperatures due to a high mass accretion rate under an advection-dominated accretion scenario. We would also compare our results with other ULXs showing flaring events and try to draw a generalized picture of the origin of such flares in these highly luminous compact objects.
- Publication:
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44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.2374G