Relativistic collapse and explosion of rotating supermassive stars with thermonuclear effects

TL;DR

This study uses general relativistic simulations to explore how rotating supermassive stars with thermonuclear effects either explode or collapse into black holes, depending on their metallicity and rotation, revealing critical thresholds for these outcomes.

Contribution

It provides the first detailed relativistic simulation results showing the influence of rotation and metallicity on supermassive star collapse and explosion outcomes, including neutrino emission characteristics.

Findings

Stars with >0.007 metallicity explode if non-rotating

Rotation lowers the metallicity threshold for explosion to ~0.001

Neutrino luminosities reach ~10^{55} erg/s during collapse

Abstract

We present results of general relativistic simulations of collapsing supermassive stars with and without rotation using the two-dimensional general relativistic numerical code Nada, which solves the Einstein equations written in the BSSN formalism and the general relativistic hydrodynamics equations with high resolution shock capturing schemes. These numerical simulations use an equation of state which includes effects of gas pressure, and in a tabulated form those associated with radiation and the electron-positron pairs. We also take into account the effect of thermonuclear energy released by hydrogen and helium burning. We find that objects with a mass of 5x10^{5} solar mass and an initial metallicity greater than Z_{CNO}~0.007 do explode if non-rotating, while the threshold metallicity for an explosion is reduced to Z_{CNO}~0.001 for objects uniformly rotating. The critical initial metallicity for a thermonuclear explosion increases for stars with mass ~10^{6} solar mass. For those stars that do not explode we follow the evolution beyond the phase of black hole formation. We compute the neutrino energy loss rates due to several processes that may be relevant during the gravitational collapse of these objects. The peak luminosities of neutrinos and antineutrinos of all flavors for models collapsing to a BH are ~10^{55} erg/s. The total radiated energy in neutrinos varies between ~10^{56} ergs for models collapsing to a BH, and ~10^{45}-10^{46} ergs for models exploding.