The Growth of the Central Black Holes in Quasi-stars
Journal Article
Overview
abstract
Abstract; ; Observations by JWST have confirmed the presence of supermassive black holes (BHs) at redshifts; z; ≳ 10, lending support to scenarios in which BHs experience rapid growth through intense gas accretion. Here we investigate the growth of a BH embedded at the center of a quasi-star, a theoretically predicted object formed via direct collapse. In a quasi-star, the central BH accretes at a highly super-Eddington rate, while the excess energy is transported outward by convection and radiated at approximately the Eddington luminosity of the entire star. We employ the open-source stellar evolution code; MESA; to construct quasi-star models and follow the time-dependent growth of the central BH under different prescriptions for the accretion rate at the inner boundary; R; ; i; ; , and further considering the effect of winds. For the case; R; ; i; ; = ; NR; B; , where; N; is a constant and; R; B; is the Bondi radius corresponding to the mass of the BH and the gas infalling onto it, our models terminate when the BH mass reaches a critical value; ; ; ; ; ; ; ; M; ; ; crit; ; ; (; N; ); =; ; ; c; ; ; s; ,; i; ; ; 3; ; ; /; (; 12; ; ; ; ; N; ; ; 3; ; ; ; ; G; ; ; 3; ; ; π; ; ; ρ; ; ; i; ; ; ; ; ); ; ; (where; c; ; s; ,; i; ; and; ρ; ; i; ; are the sound speed and density at; R; ; i; ; , respectively), a limit we also derive analytically. Models that feature an inner convective region matched to an outer adiabatic envelope exhibit BH growth up to approximately; M; BH; /; M; ⋆; ≃ 0.33, largely independent of the stellar mass; M; ⋆; itself. This ratio is approximately preserved even in the presence of mass loss, as several properties of the model are independent of the quasi-star’s total mass.;
