Universität zu Köln

Subroweit, Matthias, Mossoux, Enmanuelle and Eckart, Andreas ORCID: 0000-0001-6049-3132 (2020). Synchrotron Self-Compton Scattering in Sgr A* Derived from NIR and X-Ray Flare Statistics. Astrophys. J., 898 (2). BRISTOL: IOP PUBLISHING LTD. ISSN 1538-4357

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Abstract

The flaring activity of Sagittarius A* (Sgr A*) can be analyzed by statistical means to test emission models for its accretion flow. A particular modeling question is whether the observed X-ray flares are the high-energy end of a synchrotron spectrum or if they arise from self-Comptonized photons of a lower-energy synchrotron process. We use already published Chandra X-ray Visionary Project data to statistically investigate the X-ray count-rate distribution of Sgr A*. Two previous workgroups have already undertaken such an analysis on that data. They modeled the flaring part of the emission with a bounded power law, i.e., a power-law distribution with a hard cutoff at the highest measured count rate. With this model, both teams obtain a power-law index a(X) similar to 2. We show that the flare count-rate distribution can also be well described by a truncated, i.e., an exponentially decaying power law. We argue that an exponential truncation is a more natural model than a hard cutoff. With this alternate model, our fit yields a power-law index alpha(X) similar to 1.66. We find that this slope can be canonically explained by a synchrotron self-Compton (SSC) process. Therefore, we argue that SSC models are the best ones suitable to explain the observed X-ray count-rate distribution.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Subroweit, Matthias UNSPECIFIED UNSPECIFIED UNSPECIFIED Mossoux, Enmanuelle UNSPECIFIED UNSPECIFIED UNSPECIFIED Eckart, Andreas UNSPECIFIED orcid.org/0000-0001-6049-3132 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-324916
DOI:	10.3847/1538-4357/ab9947
Journal or Publication Title:	Astrophys. J.
Volume:	898
Number:	2
Date:	2020
Publisher:	IOP PUBLISHING LTD
Place of Publication:	BRISTOL
ISSN:	1538-4357
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics I
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SUPERMASSIVE BLACK-HOLE; GALACTIC-CENTER; INFRARED-EMISSION; STELLAR ORBITS; XMM-NEWTON; SAGITTARIUS; VARIABILITY; MODEL; SPECTRUM; A(STAR) Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/32491