Simulating the Magnetorotational Collapse of Supermassive Stars: Incorporating Gas Pressure Perturbations and Different Rotation Profiles

Collapsing supermassive stars with masses M≳10⁴⁻⁶M⊙ have long been speculated to be the seeds of supermassive black holes. We previously performed GRMHD simulations of marginally stable magnetized Γ=4/3 polytropes uniformly rotating at the mass-shedding limit to model the direct collapse of SMSs and obtained a black hole-disk system which launched an incipient jet. Here we perform GRMHD simulations of Γ≳4/3 polytropes to account for the perturbative role of gas pressure in SMSs. 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 to the stellar exterior. We find that the mass of BH depends sharply on Γ−4/3 and the initial stellar rotation profile. Following the BH formation, a jet is launched and its duration is consistent with 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.