# Spin light of neutrino in astrophysical environments

## TL;DR

This paper explores the spin light of neutrino ($SL
u$), a potential electromagnetic radiation mechanism for high-energy neutrinos in dense astrophysical environments, analyzing conditions under which it could be significant.

## Contribution

The study provides an advanced analysis of $SL
u$ in matter, identifying astrophysical settings and conditions where this effect could be observable, especially in dense neutron star matter and high-energy neutrinos.

## Key findings

- $SL
u$ may be significant for ultra-high energy neutrinos in dense matter.
- Conditions for $SL
u$ are most favorable in neutron star environments and galaxy clusters.
- The effect's polarization properties could relate to gamma-ray burst polarization observations.

## Abstract

The ${\it {spin \ \ light \ \ of \ \ neutrino}}$ ($SL\nu$) is a new possible mechanism of electromagnetic radiation by a massive neutrino (with a nonzero magnetic moment) moving in media. Since the prediction of this mechanism, the question has been debated in a number of publications as whether the effect can be of any significance for realistic astrophysical conditions. Although this effect is strongly suppressed due to smallness of neutrino magnetic moment, for ultra-high energy neutrinos (PeV neutrinos recently observed by the IceCube collaboration, for instance) the $SL\nu$ might be of interest in the case of neutrinos propagating in dense matter. An advanced view on the $SL\nu$ in matter is given, and several astrophysical settings (a neutron star, supernova, Gamma-Ray Burst (GRB), and relic neutrino background) for which the effect can be realized are considered. Taking into account the threshold condition and also several competing processes, we determine conditions for which the $SL\nu$ mechanism is possible. We conclude that the most favorable case of the effect manifestation is provided by ultra dense matter of neutron stars and ultrahigh energy of the radiating neutrino, and note that these conditions can be met within galaxy clusters. It is also shown that due to the $SL\nu$ specific polarization properties this electromagnetic mechanism is of interest in the connection with the observed polarization of GRB emission.