Asymmetric Dark Matter Imprint on Low-mass Main-sequence Stars in the Milky Way Nuclear Star Cluster

Abstract

In this work, we study the impact of asymmetric dark matter (ADM) on low-mass main-sequence stars in the Milky Way's nuclear star cluster, where the dark matter (DM) density is expected to be orders of magnitude above what is found near the Sun (${\rho }_{\mathrm{DM}}\gtrsim {10}^{3}\ \mathrm{GeV}\ {\mathrm{cm}}^{-3}$). Using a modified stellar evolution code and considering a DM particle ($m_{\chi} = 4 \text{ GeV}$) with a spin-dependent interaction cross section close to the limits allowed by direct detection, we found that the interactions of ADM with baryons in the star's core can have two separate effects on the evolution of these stars: a decrease in the hydrogen burning rate, extending the duration of the main-sequence of stars with $M ~ 1M_{\odot}$ by a few Gyr; the suppression of the onset of convection in the core of stars with $M \lesssim 1.5M_{\odot}$ and consequent quench of supply for the nuclear reactions. If we consider $\rho_{\text{DM}} > 10^3 \ \text{GeV cm}^{-3}$ (corresponding to the inner 5 pc of the Milky Way), stars lighter than the Sun will have a main-sequence life span comparable to the current age of the universe. Stars heavier than two solar masses are not sensitive to the DM particles considered here.