Neutrino emission from neutron star matter

TL;DR

This paper reviews neutrino emission processes in neutron star matter, discussing weak interactions, reaction mechanisms, and recent theoretical advances relevant to neutron star cooling and composition.

Contribution

It provides a comprehensive overview of neutrino emission reactions in neutron star cores and analyzes recent progress and future prospects in the field.

Findings

Neutrino emission dominates neutron star cooling after ~50 seconds.

Weak interactions of nucleons are crucial for understanding star composition.

Recent theoretical developments improve modeling of neutrino processes.

Abstract

The temperature of a newly formed neutron star is believed to be as high as $10^{11}$~K, corresponding to a thermal energy of about $10$ MeV. After a time $t \sim 50 \ {\rm s}$, the neutrino mean free path in nuclear matter exceeds the typical star radius, R~$\sim$~10 Km, and neutrino emission becomes the dominant mechanism of energy loss, eventually bringing the temperature down to $\sim10^{8}$~K. Neutrinos also play a critical role in determining the composition of matter in the star interior, consisting primarily of a charge-neutral mixture of neutrons, protons and leptons in $\beta$-equilibrium. This article provides an introduction to the weak interactions of nucleons in nuclear matter, as well as a concise review of the neutrino emission reactions taking place in the neutron star core. The approximations involved in the standard theoretical treatment of thermal and dynamical effects are analysed in the light of the recent progress of the field, and the prospects for future developments are outlined.