Speaker
Description
Data from the Fermi-Large Area Telescope has revealed some strong, unexplained, diffuse, non-thermal emission coming from the Galactic bulge which is prominent in the gamma-ray energy range 1-10 GeV with a peak at ~2 GeV. This extended gamma-ray excess in the Milky Way center has been labeled the Galactic center gamma-ray excess (GCE). The origin of the GCE has been vigorously discussed in the literature and the proposed sources include self-annihilating WIMP dark matter and a previously unknown population of millisecond pulsars (MSPs). Here we investigate a potential origin for this putative MSP population by constructing a synthetic MSP population using the Binary Stellar Evolution (BSE) module of the Astrophysical Multipurpose Software Environment (AMUSE). Specifically, we want to establish whether gamma-ray emission from an MSP population arising from the accretion induced collapse (AIC) of O-Ne white dwarfs in Galactic bulge binary systems can explain the GCE. Furthermore, we investigate the X-ray emission from the neutron stars that, after AIC has occurred, accretes further mass from their companion stars. The X-ray and gamma-ray emission of the synthetic population are traced across cosmic time to determine whether it can explain the GCE while simultaneously satisfying the observed upper limits given by the number of bright (L_x>10^36 erg/s), low-mass X-ray binaries (LMXBs) in the Inner Galaxy. We find that a population of MSPs formed in the Galactic bulge via AIC of massive WDs and the following LMXB phase satisfy all current observational constraints. This putative population of MSPs in the inner Galaxy can self consistently explain the Galactic center gamma-ray excess.
