Millisecond pulsars and the Galactic Center gamma-ray excess: the importance of luminosity function and secondary emission

Jovana Petrovic, Pasquale D. Serpico, Gabrijela Zaharijas

Published 2014-11-11Version 1

Recently, several groups of authors have analyzed Fermi LAT data in a region around the Galactic center finding an unaccounted gamma-ray excess over diffuse backgrounds in the GeV energy range. Here we test the possibility that this excess is produced by a population of yet unresolved millisecond pulsars (MSPs) located in the bulge of the Milky Way. We rely on the MSP characteristics reported by the 2PC catalogue, use the package GALPLOT to simulate this population, and compare our results to what has been detected and flagged as 'gamma ray excess'. We find that the conclusions strongly depend on the details of the MSP luminosity function (in particular, its high luminosity end) as well as on the possible secondary emission of the MSP population. Within current uncertainties, a large if not dominant contribution to the excess cannot be excluded. We also compute the number of MSP expected to be detected with a relatively minor improvement over the current Fermi LAT point source sensitivity, with promising perspectives for future instruments or possibly already for the performances expected for the latest LAT data analysis (Pass 8).