arXiv subjects

Adriana R. Raduta

Publications and source records attributed to Adriana R. Raduta.

21 records · Page 2Linked to original sources

arXiv2020

Proto-neutron stars with heavy baryons and universal relations

We use covariant density functional theory to obtain the equation of state (EoS) of matter in compact stars at non-zero temperature, including the full baryon octet as well as the $Δ(1232)$ resonance states. Global properties of hot $Δ$-admixed hypernuclear stars are computed for fixed values of entropy per baryon ($S/A$) and lepton fraction ($Y_L$). Universal relations between the moment of inertia, quadrupole moment, tidal deformability, and compactness of compact stars are established for fixed values of $S/A$ and $Y_L$ that are analogous to those known for cold catalyzed compact stars. We also verify that the $I$-Love-$Q$ relations hold at finite temperature for constant values of $S/A$ and $Y_L$.

nucl-th↗

arXiv2019

Cooling of hypernuclear compact stars: Hartree-Fock models and high-density pairing

The thermal evolution of hypernuclear compact stars is studied for stellar models constructed on the basis of covariant density functional theory in Hartree and Hartree-Fock approximation. Parametrizations of both types are consistent with the astrophysical mass constraints on compact stars and available hypernuclear data. We discuss the differences of these density functionals and highlight the effects they have on the composition and on the cooling of hypernuclear stars. It is shown that hypernuclear stars computed with density functional models that have a low symmetry energy slope, $L$, are fairly consistent with the cooling data of observed compact stars. The class of stellar models based on larger $L$ values gives rise to the direct Urca process at low densities, which leads to significantly faster cooling. We conjecture high-density pairing for protons and $Λ$'s in the $P$-wave channel and provide simple scaling arguments to obtain these gaps. As a consequence the most massive stellar models with masses $1.8 \le M/M_{\odot} \le2$ experience slower cooling by hyperonic dUrca processes which involve $Λ$'s and protons.

nucl-th↗

arXiv2018

Cooling of hypernuclear compact stars

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 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 $M/M_{\odot} \ge 1.5$ the neutrino cooling is dominated by hyperonic direct Urca processes in general. In the low-mass stars the $(Λp)$ 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 $Λ$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 $(Λp)$ channel because they develop inner cores where the $S$-wave pairing of $Λ$s and proton is absent.

astro-ph.HE↗