A new open-source code for spherically symmetric stellar collapse to neutron stars and black holes

Abstract

We present the new open-source spherically-symmetric general-relativistic\n(GR) hydrodynamics code GR1D. It is based on the Eulerian formulation of GR\nhydrodynamics (GRHD) put forth by Romero-Ibanez-Gourgoulhon and employs\nradial-gauge, polar-slicing coordinates in which the 3+1 equations simplify\nsubstantially. We discretize the GRHD equations with a finite-volume scheme,\nemploying piecewise-parabolic reconstruction and an approximate Riemann solver.\nGR1D is intended for the simulation of stellar collapse to neutron stars and\nblack holes and will also serve as a testbed for modeling technology to be\nincorporated in multi-D GR codes. Its GRHD part is coupled to various\nfinite-temperature microphysical equations of state in tabulated form that we\nmake available with GR1D. An approximate deleptonization scheme for the\ncollapse phase and a neutrino-leakage/heating scheme for the postbounce epoch\nare included and described. We also derive the equations for effective rotation\nin 1D and implement them in GR1D. We present an array of standard test\ncalculations and also show how simple analytic equations of state in\ncombination with presupernova models from stellar evolutionary calculations can\nbe used to study qualitative aspects of black hole formation in failing\nrotating core-collapse supernovae. In addition, we present a simulation with\nmicrophysical EOS and neutrino leakage/heating of a failing core-collapse\nsupernova and black hole formation in a presupernova model of a 40 solar mass\nzero-age main-sequence star. We find good agreement on the time of black hole\nformation (within 20%) and last stable protoneutron star mass (within 10%) with\npredictions from simulations with full Boltzmann neutrino radiation\nhydrodynamics.\n