We present a new overview of the life of very massive stars (VMS) in terms of neutrino emission from thermal processes: pair annihilation, plasmon decay, photoneutrino process, bremsstrahlung and recombination processes in burning stages of selected VMS models. We use the realistic conditions of temperature, density, electron fraction and nuclear isotropic composition of the VMS. Results are presented for a set of progenitor stars with mass of 150, 200 and 300 M$_odot$ Z=0.002 and 500 M$_odot$ Z=0.006 rotating models which are expected to explode as a pair instability supernova at the end of their life except the 300 M$_odot$ would end up as a black hole. It is found that for VMS, thermal neutrino emission occurs as early as towards the end of hydrogen burning stage due to the high initial temperature and density of these VMS. We calculate the total neutrino emissivity, $Q_ u$ and luminosity, $L_ u$ using the structure profile of each burning stages of the models and observed the contribution of photoneutrino at early burning stages (H and He) and pair annihilation at the advanced stages. Pair annihilation and photoneutrino processes are the most dominant neutrino energy loss mechanisms throughout the evolutionary track of the VMS. At the O-burning stage, the neutrino luminosity $sim 10^{47-48}$ erg/s depending on their initial mass and metallicity are slightly higher than the neutrino luminosity from massive stars. This could shed light on the possibility of using detection of neutrinos to locate the candidates for pair instability supernova in our local universe.
تحميل البحث