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Statistical and theoretical studies of flares from Sagittarius A⋆

Published online by Cambridge University Press:  09 February 2017

Ya-Ping Li ,
Qiang Yuan ,
Q. Daniel Wang ,
P. F. Chen ,
Joseph Neilsen ,
Taotao Fang ,
Shuo Zhang  and
Jason Dexter
Ya-Ping Li
Affiliation:
Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China email: leeyp2009@gmail.com Department of Astronomy and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, Fujian 361005, China
Qiang Yuan
Affiliation:
Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Science, Nanjing, 210008, China Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
Q. Daniel Wang
Affiliation:
Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
P. F. Chen
Affiliation:
School of Astronomy and Space Science, Nanjing University, Nanjing 210023, China
Joseph Neilsen
Affiliation:
MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA 02139, USA
Taotao Fang
Affiliation:
Department of Astronomy and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, Fujian 361005, China
Shuo Zhang
Affiliation:
Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027, USA
Jason Dexter
Affiliation:
Max Planck Institute for Extraterrestrial Physics, P.O. Box 1312, Giessenbachstr., D-85741 Garching, Germany
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Abstract

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Multi-wavelength flares have routinely been observed from the supermassive black hole, Sagittarius A⋆ (Sgr A⋆), at our Galactic center. The nature of these flares remains largely unclear, despite many theoretical models. We study the statistical properties of the Sgr A⋆ X-ray flares and find that they are consistent with the theoretical prediction of the self-organized criticality system with the spatial dimension S = 3. We suggest that the X-ray flares represent plasmoid ejections driven by magnetic reconnection (similar to solar flares) in the accretion flow onto the black hole. Motivated by the statistical results, we further develop a time-dependent magnetohydrodynamic (MHD) model for the multi-band flares from Sgr A⋆ by analogy with models of solar flares/coronal mass ejections (CMEs). We calculate the X-ray, infrared flare light curves, and the spectra, and find that our model can explain the main features of the flares.

Keywords

Galaxy: center – black hole physics – accretion, accretion disks – methods: statistical – MHD
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 11 , Symposium S322: The Multi-Messenger Astrophysics of the Galactic Centre , July 2016 , pp. 31 - 38
Copyright
Copyright © International Astronomical Union 2017 

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