Exploring plasma evolution during Sagittarius A* flares

TL;DR

This paper models the plasma evolution during Sagittarius A* flares by self-consistently calculating particle distributions and radiative processes, providing insights into flare mechanisms and plasma conditions.

Contribution

It introduces a comprehensive spectral modeling approach that accounts for non-thermal processes and plasma parameter changes during Sgr A* flares, improving understanding of emission mechanisms.

Findings

Non-thermal synchrotron emission explains the infrared to X-ray spectrum.

Particle distributions can significantly deviate from standard assumptions.

Density increase from G2 encounter affects quiescent emission.

Abstract

We present a new way of describing the flares from Sgr A* with a self-consistent calculation of the particle distribution. All relevant radiative processes are taken into account in the evolution of the electron distribution and resulting spectrum. We present spectral modelling for new X-ray flares observed by NuSTAR, together with older observations in different wavelengths, and discuss the changes in plasma parameters to produce a flare. We show that under certain conditions, the real particle distribution can differ significantly from standard distributions assumed in most studies. We conclude that the flares are likely generated by magnetized plasma consistent with our understanding of the accretion flow. Including non-thermal acceleration, injection, escape, and cooling losses produces a spectrum with a break between the infrared and the X-ray, allowing a better simultaneous description of the different wavelengths. We favour the non-thermal synchrotron interpretation, assuming the infrared flare spectrum used is representative. We also consider the effects on Sgr A*s quiescent spectrum in the case of a density increase due to the G2 encounter with Sgr A*.