2011MNRAS.414..495R

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_∼ 10³⁰ erg/s at the Galactic Centre distance. We show that the luminosity function of these CBF sources agrees well with the luminosity function of sources in the solar vicinity. The cumulative luminosity density of sources detected in the CBF in the luminosity range 10³⁰–10³² erg/s per unit stellar mass is L_2-10 keV_/M_*= (1.7±0.3) {x} 10²⁷ erg/s/M_☉. Taking into account sources in the luminosity range 10³²–10³⁴ erg/s from [Sazonov et al. 2006], the cumulative luminosity density in the broad luminosity range 10³⁰–10³⁴ erg/s becomes L_2-10 keV_/M_*= (2.4±0.4) {x} 10²⁷ erg/s/M_☉. 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.