Dark Matter annihilations in Pop III stars

Abstract

We study the impact of the capture and annihilation of Weakly Interacting Massive Particles (WIMPs) on the evolution of Pop III stars. With a suitable modification of the Geneva stellar evolution code, we study the evolution of 20 and 200 M${}_{\odot }$ stars in Dark Matter Haloes with densities between 10${}^8$ and $10^{11}$ GeV/cm${}^3$ during the core H-burning phase, and, for selected cases, until the end of the core He-burning phase. We find that for WIMP densities higher than 5.3 $10^{10}({\sigma }_p^{SD}/10^{-38}{cm}^2{)}^{-1}$ GeV cm${}^{-3}$ the core H-burning lifetime of $20M_{\odot }$ and $200M_{\odot }$ stars exceeds the age of the Universe, and stars are sustained only by WIMP annihilations. We determine the observational properties of these `frozen` objects and show that they can be searched for in the local Universe thanks to their anomalous mass-radius relation, which should allow unambiguous discrimination from normal stars.

Comments: 4 pages, 4 figures