# Neutron stars: the equation of state, superconductivity/superfluidity and transport coefficients (PHAROS WG1+WG2 meeting)

Sep 26 – 28, 2018
Department of Physics (University of Coimbra)
Europe/Lisbon timezone

## Cooling of hypernuclear compact stars

Sep 27, 2018, 8:30 AM
30m
Room E10A

### Description

We study the thermal evolution of hypernuclear compact stars
constructed from covariant density functional theory of hypernuclear
matter and parameterizations which produce sequences of stars
containing two-solar-mass objects. For the input in the simulations,
we solve the BCS gap equations in the hyperonic sector and obtain
the gaps in the spectra of $\Lambda$, $\Xi^0$ and $\Xi^-$
hyperons. For the models with masses $M/M_{\odot} \ge 1.5$ the
neutrino cooling is dominated by hyperonic direct Urca processes in
general. In the low-mass stars the $(\Lambda p)$ plus leptons
channel is the dominant direct Urca process, whereas for more
massive stars the purely hyperonic channels $(\Sigma^-\Lambda)$ and
$(\Xi^-\Lambda)$ are dominant. Hyperonic pairing strongly
suppresses the processes on $\Xi^-$s and to a lesser degree on
$\Lambda$s. We find that intermediate-mass $1.5 \le M/M_{\odot} \le 1.8$ models have surface temperatures which lie within the range
inferred from thermally emitting neutron stars, if the hyperonic
pairing is taken into account. Most massive models with $M/M_{\odot} \simeq 2$ may cool very fast via the direct Urca process through the
$(\Lambda p)$ channel because they develop inner cores where the
$S$-wave pairing of $\Lambda$s and proton is absent.