Synchrotron Blob Model of Infrared and X-ray Flares from Sagittarius A${}^{\ast }$

Abstract

Sagittarius A${}^{\ast }$ in the Galactic center harbors a supermassive black hole and exhibits various active phenomena. Besides quiescent emission in radio and submillimeter radiation, flares in the near infrared (NIR) and X-ray bands are observed to occur frequently. We study a time-dependent model of the flares, assuming that the emission is from a blob ejected from the central object. Electrons obeying a power law with the exponential cutoff are assumed to be injected in the blob for a limited time interval. The flare data of 2007 April 4 were used to determine the values of model parameters. The spectral energy distribution of flare emission is explained by nonthermal synchrotron radiation in the NIR and X-ray bands. The model light curves suggest that electron acceleration is still underway during the rising phase of the flares. GeV gamma-rays are also emitted by synchrotron self-Compton scattering, although its luminosity is not strictly constrained by the current model. If the GeV emission is faint, the plasma blob is dominated by the magnetic energy density over the electron kinetic energy density. Observations in the GeV band will clarify the origin of the blob.

11 pages, 8 figures, 1 table. The title is slightly changed and references are updated. Minor corrections are also included

References in corpus (5)

• Polarimetry of near-infrared flares from Sagittarius A*
• A Constant Spectral Index for Sagittarius A* During Infrared/X-ray Intensity Variations
• A Magnetohydrodynamic Model for the Formation of Episodic Jets
• X-ray hiccups from SgrA* observed by XMM-Newton. The second brightest flare and three moderate flares caught in half a day
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• The origin of hotspots around Sgr A*: Orbital or pattern motion?
• An Inverse Compton Scattering Origin of X-ray Flares from Sgr A*
• A magnetohydrodynamic model for multi-wavelength flares from Sagittarius~A${}^{\star }$ (I): model and the near-infrared and X-ray flares
• A Leptonic Model of Steady High-Energy Gamma-Ray Emission from Sgr A${}^{\ast }$
• Forward Ray Tracing and Hot Spots in Kerr Spacetime