Spectrum Composition of Galactic Center X-ray Emission with Point and Diffuse X-ray Sources

TL;DR

This study models the Galactic Center X-ray emission spectrum by combining point source contributions and diffuse plasma components, revealing past high-energy activity of Sgr A* and providing a comprehensive quantitative understanding.

Contribution

It presents the first quantitative spectral model of the GCXE incorporating both point sources and diffuse recombining plasmas, highlighting the role of past Sgr A* activity.

Findings

The spectrum is explained by active binaries, CVs, cold matter, and diffuse sources.

Adding diffuse recombining plasmas significantly improves spectral fit.

Evidence suggests Sgr A* was active over 1000 years ago.

Abstract

This paper reports that the X-ray spectrum from the Galactic Center X-ray Emission (GCXE) is expressed by the assembly of active binaries, non-magnetic Cataclysmic Variables, magnetic Cataclysmic Variables (X-ray active star: XAS), cold matter and diffuse sources. In the fitting of the limited components of the XASs, the GCXE spectrum exhibits significant excesses with $\chi^2/d.o.f. =5.67$. The excesses are found at the energies of K$\alpha$, He$\alpha$, Ly$\alpha$ and radiative recombination continuum of S, Fe and Ni. By adding components of the cold matter and the diffuse sources, the GCXE spectrum is nicely reproduced with $\chi^2/d.o.f. = 1.53$, which is a first quantitative model for the origin of the GCXE spectrum. The drastic improvement is mainly due to the recombining plasmas in the diffuse sources, which indicate the presence of high-energy activity of Sgr A$^*$ in the past of $> 1000$~years.