Issue |
A&A
Volume 688, August 2024
|
|
---|---|---|
Article Number | L12 | |
Number of page(s) | 12 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202451146 | |
Published online | 06 August 2024 |
Letter to the Editor
General relativistic effects and the near-infrared variability of Sgr A*
II. A systematic approach to temporal asymmetry
1
Max-Planck-Institute für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
2
University of Illinois, Urbana-Champagne, USA
3
Italian ALMA Regional Centre, INAF-Istituto di Radioastronomia, Via P. Gobetti 101, 40129 Bologna, Italy
4
Max Planck Institut for Extraterrestrial Physics, 85748 Garching bei Muenchen, Germany
5
Physics and Astronomy Department, University of California, Los Angeles, CA 90095-1547, USA
6
Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
7
Department of Physics, TUM School of Natural Sciences, Technical University of Munich, 85748 Garching, Germany
Received:
17
June
2024
Accepted:
9
July
2024
A systematic study, based on the third-moment structure function, of Sgr A*’s variability finds an exponential rise time, τ1,obs = 14.8−1.5+0.4 minutes, and decay time, τ2,obs = 13.1−1.4+1.3 minutes. This symmetry of the flux-density variability is consistent with earlier work, and we interpret it as being caused by the dominance of Doppler boosting, as opposed to gravitational lensing, in Sgr A*’s light curve. A relativistic, semi-physical model of Sgr A* confirms an inclination angle of i ≲ 45°. The model also shows that the emission of the intrinsic radiative process can have some asymmetry even though the observed emission does not. The third-moment structure function, which is a measure of the skewness of the light-curve increments, may be a useful summary statistic in other contexts of astronomy because it senses only temporal asymmetry; that is, it averages to zero for any temporally symmetric signal.
Key words: acceleration of particles / accretion, accretion disks / Galaxy: center
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Open access funding provided by Max Planck Society.
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