The neutrino signal from protoneutron star accretion and black hole formation

TL;DR

This paper analyzes neutrino emissions during the collapse of protoneutron stars into black holes, highlighting how different progenitor models and physical conditions influence the neutrino signals, with implications for understanding black hole formation.

Contribution

It provides detailed simulations of neutrino spectra during PNS collapse, examining dependencies on physical conditions and progenitor models, and offers a simple approximation for electron-neutrino luminosity.

Findings

Neutrino spectra vary significantly with progenitor models.

Electron-neutrino luminosity depends on conditions at the neutrinosphere.

Increasing mu/tau-neutrino luminosity correlates with PNS contraction.

Abstract

We discuss the formation of stellar mass black holes via protoneutron star (PNS) collapse. In the absence of an earlier explosion, the PNS collapses to a black hole due to the continued mass accretion onto the PNS. We present an analysis of the emitted neutrino spectra of all three flavors during the PNS contraction. Special attention is given to the physical conditions which depend on the input physics, e.g. the equation of state (EoS) and the progenitor model. The PNSs are modeled as the central object in core collapse simulations using general relativistic three-flavor Boltzmann neutrino transport in spherical symmetry. The simulations are launched from several massive progenitors of 40 and 50 solar mass. We analyze the electron-neutrino luminosity dependencies and construct a simple approximation for the electron-neutrino luminosity, which depends only on the physical conditions at the electron-neutrinosphere. In addition, we analyze different mu/tau-neutrino pair-reactions separately and compare the differences during the post-bounce phase of failed core collapse supernova explosions of massive progenitors. We also investigate the connection between the increasing mu/tau-neutrino luminosity and the PNS contraction during the accretion phase before black hole formation. Comparing the different post bounce phase of the progenitor models under investigation, we find large differences in the emitted neutrino spectra. These differences and the analysis of the electron-neutrino luminosity indicate a strong progenitor model dependency of the emitted neutrino signal.