MeV Neutrinos from Astrophysical Sources

Many astrophysical sources can emit neutrinos in the energy below a few to several MeVs. Detecting such neutrinos will provide us with valuable information on the physical processes that govern their evolution and structure. So far, neutrinos only from the Sun and a single event of supernova (SN 1987A) have been observed. However, as the size of neutrino observatories keep increasing and the detector technology keep improving, astrophysical neutrinos, other than from the Sun and nearby supernovae including oxygen or silicon burning stars near supernovae, will be eventually observable, opening the era of the neutrino astronomy. In this work, we search for possibilities to observe astrophysical neutrinos from various sources, but we focus more on red supergiant (RSG) stars as our primary candidate, which are expected to emit the amount of neutrinos much larger than the Sun. We calculated neutrino luminosities along the evolutionary tracks of massive stars of 15 - 25 Msun with metallicity 0.01 – 1 Zsun, using MESA, a publicly available stellar evolution code. We then calculated the energy spectra of neutrinos emitted through various production processes. We present the fluxes of such neutrinos from nearby RSGs on the Earth, and discuss the prospect of detecting them in current and future neutrino observatories.