Rapid Cooling of the Neutron Star in Cassiopeia A Triggered by Neutron Superfluidity in Dense Matter

TL;DR

This paper explains the rapid cooling of the Cassiopeia A neutron star as caused by neutron superfluidity and proton superconductivity, predicting ongoing cooling observable over decades.

Contribution

It introduces a model linking neutron superfluidity onset to observed cooling, providing a new explanation for the star's temperature decline.

Findings

Neutron superfluid transition occurs at ~0.5x10^9 K.

Protons are in a superconducting state with higher critical temperature.

Cooling will continue at the current rate for several decades.

Abstract

We propose that the observed cooling of the neutron star in Cassiopeia A is due to enhanced neutrino emission from the recent onset of the breaking and formation of neutron Cooper pairs in the 3P2 channel. We find that the critical temperature for this superfluid transition is ~0.5x10^9 K. The observed rapidity of the cooling implies that protons were already in a superconducting state with a larger critical temperature. Our prediction that this cooling will continue for several decades at the present rate can be tested by continuous monitoring of this neutron star.