General Relativistic Effects in the Core Collapse Supernova Mechanism

Abstract

We apply our recently developed code for spherically symmetric, fully general relativistic (GR) Lagrangian hydrodynamics and multigroup Ñux-limited di †usion (MGFLD) neutrino transport to examine the e †ects of GR on the hydrodynamics and transport during collapse, bounce, and the critical shock reheating phase of core collapse supernovae. GR e †ects were examined by performing core collapse simulations from several precollapse models in the Newtonian limit, in a hybrid limit consisting of GR hydrodynamics and Newtonian transport, and in the fully GR limit. Comparisons of models computed with GR versus Newtonian hydrodynamics show that collapse to bounce takes slightly less time in the GR limit and that the shock propagates slightly farther out in radius before receding. After a secondary quasi-static rise in the shock radius, the shock radius declines considerably more rapidly in the GR simulations than in the corresponding Newtonian simulations. During the shock reheating phase, core collapse computed with GR hydrodynamics results in a substantially more compact structure from the center out to the stagnated shock, the shock radius being reduced by a factor of 2 after 300 ms for a 25 model and 600 ms for a 15 model, times being measured from bounce. The inÑow speed of M _ M _ material behind the shock is also increased by about a factor of 2 throughout most of the evolution as a consequence of GR hydrodynamics. Regarding neutrino transport, comparisons show that the luminosity and rms energy of any neutrino Ñavor during the shock reheating phase increases when switching from Newtonian to GR hydrodynamics. This arises from the close coupling of the hydrodynamics and transport and the e †ect of GR hydrodynamics to produce more compact core structures, hotter neutrinospheres at smaller radii. On additionally switching from Newtonian to GR transport, gravitational time dilation and redshift e †ects decrease the luminosities and rms energies of all neutrino Ñavors. This decrease is less in magnitude than the increase in neutrino luminosities and rms energies that arise when switching from Newtonian to GR hydrodynamics, with the result that a fully GR simulation gives higher neutrino luminosities and harder neutrino spectra than a fully Newtonian simulation of the same precollapse model.

Explosion Mechanisms of Massive Stars

“…There is no controversy about that. All computations are in agreement, independent of Newtonian or relativistic gravity and independent of the neutrino transport being treated in an approximate way by flux-limited diffusion methods (e.g., Myra et al 1987;Myra & Bludman 1989;Bruenn 1993;Bruenn, De Nisco, & Mezzacappa 2001) or very elaborately by solving the frequencyand angle-dependent Boltzmann transport equation (Rampp & Janka 2000;Mezzacappa et al 2001;Liebendörfer et al 2001;Liebendörfer et al 2002).…”

The Development of Explosions in Axisymmetric Ab Initio Core-Collapse Supernova Simulations of 12–25 Stars

“…12 3 r > -The transport solver is an improved and updated version of the multi-group (frequency) flux-limited diffusion (MGFLD) transport solver of Bruenn (1985), enhanced for GR (Bruenn et al 2001), with an additional geometric flux-limiter to prevent the over-rapid transition to free streaming of the standard flux-limiter.…”

A Finite Difference Representation of Neutrino Radiation Hydrodynamics in Spherically Symmetric General Relativistic Spacetime

“…We note that, excepting the pioneering Boltzmann solver of Wilson (1971), codes with MGFLD currently provide the only alternative numerical data for the evolution of a supernova in full general relativity (Myra et al 1987;Schinder & Bludman 1989;Bruenn et al 2001). We compare the evolution of a 13 M progenitor (Nomoto & Hashimoto 1988).…”