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

Contributed Papers
Copyright © International Astronomical Union 2017 


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