http://arxiv.org/abs/1712.00584
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.
A. Raduta, A. Sedrakian and F. Weber
Tue, 5 Dec 17
63/96
Comments: 11 pages, 9 figures