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

Abstract

We study the population of low-mass X-ray binaries (LMXBs) in the Galactic bulge using the deep survey of this region by the IBIS telescope aboard the INTEGRAL observatory. Thanks to the increased sensitivity with respect to previous surveys of this field, we succeeded to probe the luminosity function (LF) of LMXBs down to ~7e34 erg/sec in the 17-60keV energy band. The slope dlog N/dlog L=-0.96+/0.20 measured in the 1e35-1e37 erg/sec range confirms that the LMXB LF flattens below L_x<1e37 erg/sec with respect to higher luminosities. We discuss the origin of the observed LF flattening. We demonstrate that the spatial distribution of persistent LMXBs in the Galactic Center/Galactic bulge region is consistent with a model of stellar mass distribution that includes the nuclear stellar disk component in the innermost degree of the Galaxy. The spatial distribution of transient LMXBs detected in the Galactic Center region indicates an increased fraction of transient sources in the innermost degree of the Galaxy with respect to outer regions.

10 pages, 8 figures, Submitted to A&A

References in corpus (6)

• A radio-emitting outflow in the quiescent state of A0620-00: implications for modelling low-luminosity black hole binaries
• INTEGRAL/IBIS all-sky survey in hard X-rays
• Hard X-ray emission from the Galactic ridge
• A study of the population of LMXBs in the bulge of M31
• Probing the Low-Luminosity XLF in Normal Elliptical Galaxies
• On the contribution of point sources to the Galactic ridge X-ray emission

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• The Gamma-Ray Pulsar Population of Globular Clusters: Implications for the GeV Excess
• Testing the millisecond pulsar scenario of the Galactic center gamma-ray excess with very high energy gamma-rays
• NuSTAR observation of a Type I X-ray burst from GRS 1741.9-2853
• Bright end of the luminosity function of high-mass X-ray binaries: contributions of hard, soft and supersoft sources
• The Galactic LMXB Population and the Galactic Centre Region
• Population synthesis of classical low-mass X-ray binaries in the Galactic Bulge
• 15 years of Galactic surveys and hard X-ray Background measurements
• Galactic model parameters of cataclysmic variables: Results from a new absolute magnitude calibration with 2MASS and WISE
• The Luminosity Function of Low Mass X-Ray Binaries in the Globular Cluster System of NGC 1399
• Faint X-ray Binaries and Their Optical Counterparts in M31
• Determining the Nature of Faint X-Ray Sources from the ASCA Galactic Center Survey