X-ray Sources in the Dwarf Spheroidal Galaxy Draco

TL;DR

This study analyzes X-ray sources in the Draco dwarf galaxy, identifying their nature, constraining the population of accreting binaries, and exploring potential dark matter decay signals.

Contribution

It provides the first detailed spectral analysis of X-ray sources in Draco, distinguishing between different source types and setting limits on black hole activity and dark matter signals.

Findings

Most sources are consistent with AGN.

Few sources could be quiescent LMXBs or CVs.

No evidence of actively accreting black hole or neutron star binaries.

Abstract

We present the spectral analysis of an 87~ks \emph{XMM-Newton} observation of Draco, a nearby dwarf spheroidal galaxy. Of the approximately 35 robust X-ray source detections, we focus our attention on the brightest of these sources, for which we report X-ray and multiwavelength parameters. While most of the sources exhibit properties consistent with AGN, few of them possess characteristics of LMXBs and CVs. Our analysis puts constraints on population of X-ray sources with $L_X>3\times10^{33}$~erg~s$^{-1}$ in Draco suggesting that there are no actively accreting BH and NS binaries. However, we find 4 sources that could be LMXBs/CVs in quiescent state associated with Draco. We also place constraints on the central black hole luminosity and on a dark matter decay signal around 3.5~keV.