Dark matter effect on the mass measurement of neutron stars

Abstract

Newly-determined mass of 1.97 $\pm$ 0.04 $M_{\odot}$ for PSR J1614-2230 has been a challenge for the neutron star with a hyperon core (namely hyperon star), since hyperons usually reduce the theoretical maximum mass of the star. In this article, we consider dark matter as another possible constituent in hyperon stars' interior to loose this mass constrain. We take dark matter as self-interacting Fermi gas with certain repulsive interaction among the dark matter particles and non-interaction between dark matter and ordinary matter as is generally assumed. We find that the star maximum mass is sensitive to the particle mass of dark matter, and a high enough star mass larger than 2 $M_{\odot}$ could be achieved when the particle mass is small enough. In this particular model, a strong upper limit 0.64 GeV for dark matter mass is obtained in strongly-interacting dark matter and 0.16 GeV for dark matter mass in weakly-interacting dark matter. Dark matter accumulated around the star could also contribute to the mass measurement, however, such contribution could be safely ignored when the generally used dark matter density is assumed.