Simulating the Magnetorotational Collapse of Supermassive Stars: Incorporating Gas Pressure Perturbations and Different Rotation Profiles
Abstract
Collapsing supermassive stars (SMSs) with masses M 104-6M have long been speculated to be the seeds that can grow and become supermassive black holes (SMBHs). We previously performed GRMHD simulations of marginally stable magnetized = 4/3 polytropes uniformly rotating at the mass-shedding limit to model the direct collapse of SMSs. These configurations are supported entirely by thermal radiation pressure and model SMSs with M 106M. We found that around 90\% of the initial stellar mass forms a spinning black hole (BH) surrounded by a massive, hot, magnetized torus, which eventually launches an incipient jet. Here we perform GRMHD simulations of 4/3, polytropes to account for the perturbative role of gas pressure in SMSs with M 106M. We also consider different initial stellar rotation profiles. The stars are initially seeded with a dynamically weak dipole magnetic field that is either confined to the stellar interior or extended from its interior into the stellar exterior. We find that the mass of the BH remnant is 90\%-99\% of the initial stellar mass, depending sharply on -4/3 as well as on the initial stellar rotation profile. After t 250-550M≈ 1-2× 103(M/106M)s following the BH formation, a jet is launched and it lasts for 104-105(M/106M)s, consistent with the duration of long gamma-ray bursts. Our results suggest that the Blandford-Znajek mechanism powers the jet. They are also in agreement with our proposed universal model that estimates accretion rates and luminosities that characterize magnetized BH-disk remnant systems that launch a jet. This model helps explain why the outgoing luminosities for vastly different BH-disk formation scenarios all reside within a narrow range ( 1052 1 erg/s), roughly independent of M.