Isotropic neutrino flux from supernova explosions in the universe
- PDF / 197,001 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 79 Downloads / 177 Views
otropic Neutrino Flux from Supernova Explosions in the Universe V. B. Petkova, b a
Institute for Nuclear Research, Russian Academy of Sciences, Moscow, 117312 Russia bInstitute of Astronomy, Russian Academy of Sciences, Moscow, 109017 Russia e-mail: [email protected]
Abstract⎯Neutrinos of all types are emitted from the gravitational collapse of massive star cores, and have been amassed in the Universe throughout the history of evolution of galaxies. The isotropic and stable flux of these neutrinos is a source of information on the spectra of neutrinos from individual supernovae and on their redshift distribution. The prospects for detecting the isotropic neutrino flux with the existing and upcoming experimental facilities and the current upper limits are discussed in this paper. DOI: 10.1134/S106377961801032X
1. INTRODUCTION Neutrino radiation plays an important role in the process of stellar evolution, and during the final phase of massive star evolution in particular (see, e.g., [1] and references therein). State-of-the-art cosmological concepts suggest that once a star is heavier than the Sun by a factor of more than eight, its evolution should end up with the gravitational collapse of the central core giving rise to a powerful neutrino burst. A supernova burst occurs as soon as the star sheds its outer envelope during the core implosion. Thus far, neutrino radiation from a single supernova has been detected. This supernova, labeled as 1987A, exploded in the Large Magellanic Cloud at a distance of 50 kpc from the Sun. Despite the relatively small statistics of detected neutrino events, this observation confirmed that neutrinos play an important role in the process of a massive star explosion [2]. Had a supernova exploded in our galaxy, its neutrino burst would be reliably detected by the existing neutrino facilities with high statistical accuracy. However, only one to three such events are predicted to occur per century [3] in agreement with the existing experimental constraints. Of all operating neutrino detectors monitoring our galaxy for neutrino bursts from stellar gravitational collapse, the total observation period is the greatest for the Baksan Underground Scintillation Telescope (BUST), which started operation in the neutrino mode on June 30, 1980 [4]. Nearly 95% of all stars in our galaxy fall within the BUST sensitivity radius of ≈20 kpc. With the data collected in 30.37 yr of net observation time (from June 30, 1980 through December 31, 2015), the mean frequency of gravitation collapses in our galaxy was constrained to be less than 0.076 per year at the 90% confidence level.
At the same time, over all the visible part of the Universe, supernova bursts occur several times per second. Therefore, gravitational collapse of the central cores of massive stars throughout the Universe provide a steady and isotropic neutrino flux. Measuring the characteristics of this neutrino flux will enable us to test the theoretical schemes of the massive star corecollapse for the events occurring either near our galaxy and
Data Loading...
