Luminosity function of faint Galactic sources in the Chandra bulge field

TL;DR

This study analyzes faint X-ray sources in the Chandra Bulge Field, revealing their luminosity distribution and suggesting most are active binary stars, with findings consistent with local Galactic populations.

Contribution

It provides the first detailed luminosity function of faint Galactic X-ray sources at the Galactic Center, extending previous local studies to the bulge region.

Findings

Luminosity function matches that of local sources.

Cumulative luminosity density quantified as ~2.4e27 erg/sec/Msun.

Most faint sources are likely active binary stars.

Abstract

We study the statistical properties of faint X-ray sources detected in the Chandra Bulge Field. The unprecedented sensitivity of the Chandra observations allows us to probe the population of faint Galactic X-ray sources down to luminosities L(2-10 keV)~1e30 erg/sec at the Galactic Center distance. We show that the luminosity function of these CBF sources agrees well with the luminosity function of sources in the Solar vicinity (Sazonov et al. 2006). The cumulative luminosity density of sources detected in the CBF in the luminosity range 1e30-1e32 erg/sec per unit stellar mass is L(2-10 keV)/M*=(1.7+/-0.3)e27 erg/sec/Msun. Taking into account sources in the luminosity range 1e32-1e34 erg/sec from Sazonov et al. (2006), the cumulative luminosity density in the broad luminosity range 1e30-1e34 erg/sec becomes L(2-10 keV)/M*=(2.4+/-0.4)e27 erg/sec/Msun. The majority of sources with the faintest luminosities should be active binary stars with hot coronae based on the available luminosity function of X-ray sources in the Solar environment.