Universität zu Köln

Karssen, G. D., Bursa, M., Eckart, A., Valencia-S, M., Dovciak, M., Karas, V. and Horak, J. (2017). Bright X-ray flares from Sgr A*. Mon. Not. Roy. Astron. Soc., 472 (4). S. 4422 - 4434. OXFORD: OXFORD UNIV PRESS. ISSN 1365-2966

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Abstract

We address a question whether the observed light curves of X-ray flares originating deep in galactic cores can give us independent constraints on the mass of the central supermassive black hole. To this end, we study four brightest flares which have been recorded from Sagittarius A*. They all exhibit an asymmetric shape consistent with a combination of two intrinsically separate peaks which occur at a certain time delay with respect to each other, and are characterized by their mutual flux ratio and the profile of raising/declining parts. Such asymmetric shapes arise naturally in the scenario of a temporary flash from a source orbiting near a supermassive black hole, at a radius of only similar to 10-20 gravitational radii. An interplay of relativistic effects is responsible for the modulation of the observed light curves: Doppler boosting, gravitational redshift, light focusing and light-travel time delays. We find the flare properties to be in agreement with the simulations (our ray-tracing code SIM5LIB). The inferred mass for each of the flares comes out in agreement with previous estimates based on orbits of stars; the latter have been observed at radii and over time-scales two orders of magnitude larger than those typical for the X-ray flares, so the two methods are genuinely different. We test the reliability of the method by applying it to another object, namely, the Seyfert I galaxy RE J1034+396.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Karssen, G. D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bursa, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Eckart, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Valencia-S, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Dovciak, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Karas, V. UNSPECIFIED UNSPECIFIED UNSPECIFIED Horak, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-209847
DOI:	10.1093/mnras/stx2312
Journal or Publication Title:	Mon. Not. Roy. Astron. Soc.
Volume:	472
Number:	4
Page Range:	S. 4422 - 4434
Date:	2017
Publisher:	OXFORD UNIV PRESS
Place of Publication:	OXFORD
ISSN:	1365-2966
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SUPERMASSIVE BLACK-HOLE; QUASI-PERIODIC OSCILLATIONS; NEAR-INFRARED POLARIMETRY; ACTIVE GALACTIC NUCLEI; SAGITTARIUS-A; RE J1034+396; XMM-NEWTON; MILKY-WAY; STELLAR KINEMATICS; ACCRETION-DISC Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/20984