An Inverse Compton Scattering Origin of X-ray Flares from Sgr A*

TL;DR

This paper investigates the origin of X-ray flares from Sgr A* by modeling inverse Compton scattering, using simultaneous X-ray and near-IR observations to constrain electron properties and flare locations.

Contribution

It provides the first detailed inverse Compton scattering model for Sgr A* flares, linking observational timing delays to electron distributions and flare sites.

Findings

X-ray peaks lag near-IR flares by minutes to tens of minutes.

Constraints on electron density and temperature in the accretion flow.

Inner disk flares show no significant X-ray delay, outer disk flares are delayed.

Abstract

The X-ray and near-IR emission from Sgr A* is dominated by flaring, while a quiescent component dominates the emission at radio and sub-mm wavelengths. The spectral energy distribution of the quiescent emission from Sgr A* peaks at sub-mm wavelengths and is modeled as synchrotron radiation from a thermal population of electrons in the accretion flow, with electron temperatures ranging up to $\sim 5-20$\,MeV. Here we investigate the mechanism by which X-ray flare emission is produced through the interaction of the quiescent and flaring components of Sgr A*. The X-ray flare emission has been interpreted as inverse Compton, self-synchrotron-Compton, or synchrotron emission. We present results of simultaneous X-ray and near-IR observations and show evidence that X-ray peak flare emission lags behind near-IR flare emission with a time delay ranging from a few to tens of minutes. Our Inverse Compton scattering modeling places constraints on the electron density and temperature distributions of the accretion flow and on the locations where flares are produced. In the context of this model, the strong X-ray counterparts to near-IR flares arising from the inner disk should show no significant time delay, whereas near-IR flares in the outer disk should show a broadened and delayed X-ray flare.