Speaker
Description
Long-term observations of the Galactic center in the X-ray band reveal a new picture of the stellar population in this densely populated region. This review will present recent studies of the region of supermassive black hole Sagittarius A using ultra-deep observations from the Chandra, Swift, and NuSTAR observatories. (1) An analysis of the X-ray spectra of more than a hundred sources within 5 parsecs of Sagittarius A revealed 13 non-thermal X-ray sources in the "central parsec" whose spectral and temporal characteristics indicate a population of quiet X-ray binaries with neutron stars (NSs) or black holes (BHs). The spatial distribution of 16 non-thermal sources (BH candidates) is consistent with the central stellar cluster, which confirms theoretical predictions about the formation of binary systems in the immediate environment of Sagittarius A. (2) Long-term monitoring of the Galactic center within a radius of 30 pc from Sagittarius A has revealed about 20 transients, including very faint transients and X-ray binaries with NS and BH. (3) The extended 10 pc emission from Sgr A, discovered by NuSTAR, indicates a population of white dwarfs with a mass of 0.9 solar masses. (4) NuSTAR's survey of the central Galaxy, several parsecs away from Sgr A, revealed a population of intermediate polars with a temperature of 20-40 keV. (5) The measurement of the X-ray background in the Galactic bulge indicates a population of dwarf novae with a characteristic emission temperature of 8 keV. These and other observations of the central part of the Galaxy will be presented in the talk.