Evolution of Primordial Stars Powered by Dark Matter Annihilation up to the Main-Sequence Stage

TL;DR

This study models primordial stars powered by dark matter annihilation, showing they can grow very large and potentially form massive black holes, with their evolution influenced by dark matter properties and accretion rates.

Contribution

It provides detailed stellar evolution simulations of dark matter-powered primordial stars, highlighting their growth to supermassive sizes and the impact of dark matter parameters.

Findings

Stars reach up to 1000 solar masses during the dark star phase.

Surface temperature remains below 10^4 K during dark star expansion.

Final stellar mass is unaffected by dark matter particle mass for m_DM <= 10 GeV.

Abstract

Primordial stars formed in the early universe are thought to be hosted by compact dark matter (DM) halos. If DM consists of Weakly Interacting Massive Particles (WIMPs), such stars may be powered by DM annihilation during the early phases of their evolutions. We study the pre-main sequence evolutions of the primordial star using a detailed stellar evolution code under the assumption that the annihilation of adiabatically contracted WIMPs DM within the star provides a sufficient energy to sustain the stellar equilibrium. We follow the evolution of accreting stars using several gas mass accretion rates derived from cosmological simulations. We show that the stellar mass becomes very large, up to 900 - 1000 M_sun when the star reaches the main-sequence phase for a reasonable set of model parameters such as DM particle mass and the annihilation cross section. During the dark star phase, the star expands over a thousand solar-radii, while the surface temperature remains below 10^4 K. The energy generated by nuclear reactions is not dominant during this phase. We also study models with different gas mass accretion rates and the DM particle masses. All our models for different DM particle masses pass the dark star phase. The final mass of the dark stars is essentially unchanged for DM mass of m_DM <= 10 GeV. Gravitational collapse of the massive dark stars will leave massive black holes with mass as large as 1000 M_sun in the early universe.