Synchrotron Blob Model of Infrared and X-ray Flares from Sagittarius A$^*$

TL;DR

This paper presents a time-dependent synchrotron blob model to explain infrared and X-ray flares from Sagittarius A*, suggesting electron acceleration during flare rise and potential GeV gamma-ray emission via synchrotron self-Compton scattering.

Contribution

The study introduces a dynamic model of flare emission from a plasma blob ejected near Sagittarius A*, incorporating electron acceleration and predicting gamma-ray emission.

Findings

Spectral energy distribution explained by nonthermal synchrotron radiation.

Electron acceleration occurs during the flare's rising phase.

Potential GeV gamma-ray emission via synchrotron self-Compton scattering.

Abstract

Sagittarius A$^*$ 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.