On the Origin of the 511 keV Emission in the Galactic Centre - AstrophysicsReport as inadecuate

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Abstract: Diffuse 511 keV line emission, from the annihilation of cold positrons, hasbeen observed in the direction of the Galactic Centre for more than 30 years.The latest high-resolution maps of this emission produced by the SPI instrumenton INTEGRAL suggest at least one component of the emission is spatiallycoincident with the distribution of ~70 luminous, low-mass X-ray binariesdetected in the soft gamma-ray band. The X-ray band, however, is generally amore sensitive probe of X-ray binary populations. Recent X-ray surveys of theGalactic Centre have discovered a much larger population >4000 of faint, hardX-ray point sources. We investigate the possibility that the positrons observedin the direction of the Galactic Centre originate in pair-dominated jetsgenerated by this population of fainter accretion-powered X-ray binaries. Wealso consider briefly whether such sources could account for unexplaineddiffuse emission associated with the Galactic Centre in the microwave the WMAP`haze- and at other wavelengths. Finally, we point out several unresolvedproblems in associating Galactic Centre 511 keV emission with the brightestX-ray binaries.

Author: Reba M. Bandyopadhyay Univ. of Florida, Joseph Silk Oxford, James E. Taylor Univ. of Waterloo, Thomas J. Maccarone Southampton

Source: https://arxiv.org/

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