Numerical Study of Stellar Core Collapse and Neutrino Emission: Probing the Spherically Symmetric Black Hole Progenitors with 3–30M_⊙Iron Cores

Abstract

The existence of various anomalous stars, such as the first stars in the universe or stars produced by stellar mergers, has been proposed recently. Some of these stars will result in black hole formation. In this study we investigate ironcore collapse and black hole formation systematically for the iron-core mass range of 3Y30 M , which has not been studied well so far. Models used here are mostly isentropic iron cores that may be produced in merged stars in the present universe, but we also employ a model that is meant for a Population III star and is obtained by evolutionary calculation. We solve numerically the general relativistic hydrodynamics and neutrino transfer equations simultaneously, treating neutrino reactions in detail under spherical symmetry. As a result, we find that massive iron cores with $10 M unexpectedly produce a bounce, owing to the thermal pressure of nucleons before black hole formation. The features of neutrino signals emitted from such massive iron cores differ in time evolution and spectrum from those of ordinary supernovae. First, the neutronization burst is less remarkable or disappears completely for more massive models, because the density is lower at the bounce. Second, the spectra of neutrinos, except the electron type, are softer, owing to the electron-positron pair creation before the bounce. We also study the effects of the initial density profile, finding that the larger the initial density gradient is, the more steeply the neutronization burst declines. Furthermore, we suggest a way to probe into the black hole progenitors from the neutrino emission and estimate the event number for the currently operating neutrino detectors.

The neutrino signal from protoneutron star accretion and black hole formation

“…The actual progenitor mass limits for these different scenarios are a subject of debate and depend on the explosion mechanism and the input physics. The fate of progenitors more massive than 75 M differs from the usual Fe-core collapse scenario by the appearance of the pairinstability, as studied by Fryer et al (2001), Linke et al (2001), , Nomoto et al (2005), Ohkubo et al (2006) and Nakazato et al (2007).…”

Supernova Neutrino Light Curves and Spectra for Various Progenitor Stars: From Core Collapse to Proto-Neutron Star Cooling

“…A detailed description of numerical simulations such as general relativistic hydrodynamics, transport, and reaction rates of neutrinos can be found in Sumiyoshi et al (2005). Referring to the resolution dependences shown in Nakazato et al (2007), we use 255 mesh points for the radial Lagrangian coordinates and 20 and 4 mesh points for the energy spectrum and angular distribution, respectively. As the initial conditions, the eight progenitor models described in the previous section are adopted, and the outer boundary is settled far from the core region.…”

Astrophysical implications of equation of state for hadron-quark mixed phase: Compact stars and stellar collapses

“…Then, they are omitted in simulations for the ordinary supernova. On the other hand, we may not be able to neglect their effects for EOS in case of black hole formation, because the density and temperature would be higher than those for the ordinary supernova [32,33].…”

“…This model is the intermediate one between the models stated above. The numerical simulation of its collapse has been already done under the Shen EOS [33].…”

“…For the details of our simulation such as the initial condition, numerical methods and convergences, see Ref. 33. In FIG.…”