Dark Matter, Positrons, and the Galactic Bulge Binary Population

A number of high-energy signals from the vicinity of the Galactic Bulge have elicited excitement as potential evidence for dark matter. We believe that at least a subset of these signals are, more likely, to ultimately derive from peculiar binarity properties amongst the Bulge stars. Specifically we hypothesise that binaries are more common and/or that they are systematically tighter in the Bulge with respect to the Disk.

This would then have the consequence that binary mass transfer and/or stellar or stellar remnant mergers are more common per unit mass of stars formed in the Bulge than in the Disk; the remnants resulting from these mergers/mass transfer episodes (millisecond pulsars, R Cor Bor stars, SN1991bg-like supernovae and other exotica) are plausible sources for the high-energy signals emanating from this region. We have made observations using the AAOmega spectrograph on the 4.0 m Anglo-Australian Telescope of a number of red giant stars in the Galactic Bulge. These observations have, for the first time, the potential to measure the binary fraction and the binary parameters amongst Bulge stars in the mass range 0.9-1.3 solar masses. These data should also signficantly help in establishing a reliable IMF for the Bulge. W

e are seeking a motivated student to process these already-collected data and, if necessary, to perform further observations.