Low-mass X-ray binaries in the bulge of the Milky Way

摘要: We study the population of low-mass X-ray binaries (LMXBs) in Galactic bulge using deep survey this region by IBIS telescope aboard INTEGRAL observatory. Thanks to increased sensitivity with respect previous surveys field, we succeeded probing luminosity function (LF) LMXBs down ∼7 × 10 34 erg/s 17−60 keV energy band. The slope LF 35 −10 37 range is d log N/ dl ogL = −0.96 ± 0.20. At these low luminosities, spectra between 2 and 60 are similar that Crab, therefore nearly equal amounts released standard (2−10 keV) hard (17−60 bands. This implies LMXB flat both 2−10 bands over range. further suggests faint end significantly flatter than its bright (above erg/s), where a logN/ ∼− 1.8 was previously measured. discuss origin flattening. also demonstrate spatial distribution persistent center/Galactic consistent model stellar mass includes nuclear disk component innermost degree Galaxy. transient detected center indicates an fraction sources Galaxy outer regions.