Cooling of hypernuclear compact stars. Issue 4 (26th December 2017) - Raduta, Adriana R
Abstract: We study the thermal evolution of hypernuclear compact stars constructed from covariant density functional theory of hypernuclear matter and parametrizations which produce sequences of stars containing two-solar-mass objects. For the input in the simulations, we solve the Bardeen–Cooper–Schrieffer gap equations in the hyperonic sector and obtain the gaps in the spectra of Λ, Ξ 0, and Ξ − hyperons. For the models with masses M /M⊙ ≥ 1.5 the neutrino cooling is dominated by hyperonic direct Urca processes in general. In the low-mass stars the (Λ p ) plus leptons channel is the dominant direct Urca process, whereas for more massive stars the purely hyperonic channels (Σ − Λ) and (Ξ − Λ) are dominant. Hyperonic pairing strongly suppresses the processes on Ξ − s and to a lesser degree on Λs. We find that intermediate-mass 1.5 ≤ M /M⊙ ≤ 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⊙ ≃ 2 may cool very fast via the direct Urca process through the (Λ p ) channel because they develop inner cores where the S -wave pairing of Λs and proton is absent.