Delta-resonances and hyperons in proto-neutron stars and merger remnants

Abstract

The equation of state (EoS) and composition of dense and hot ∆-resonance admixed hypernuclear matter is studied under conditions that are characteristic of neutron star binary merger remnants and supernovas. The cold, neutrino free regime is also considered as a reference for the astrophysical constraints on the EoS of dense matter. Our formalism uses the covariant density functional (CDF) theory successfully adapted to include the full J P = 1/2 + baryon octet and non-strange members of J P = 3/2 + decouplet with density-dependent couplings that have been suitably adjusted to the existing laboratory and astrophysical data in the nuclear and hypernuclear sectors. The effect of ∆-resonances at finite temperatures is to soften the EoS of hypernuclear matter at intermediate densities and stiffen it at high densities. At low temperatures, the heavy baryons Λ, ∆ − ,Ξ − , Ξ 0 and ∆ 0 appear in the given order if the ∆-meson couplings are close to those for the nucleon-meson couplings. As is the case for hyperons, the thresholds of ∆-resonances move to lower densities with the increase of temperature indicating a significant fraction of ∆s in the low-density subnuclear regime. We find that the ∆-resonances comprise a significant fraction of baryonic matter, of the order of 10% at temperatures of the order of several tens of MeV in the neutrino-trapped regime and, thus, may affect the supernova and binary neutron star dynamics.PACS. 9 7.60.Jd (Neutron stars) -2 6.60.+c (Nuclear matter aspects of neutron stars) -2 1.65.+f (Nuclear matter)

Exotic Baryons in Hot Neutron Stars

“…The characteristics of the temperature profile are attributed to the appearance of new particles introducing new degrees of freedom and altering the specific heat of the system which is compensated by the change in temperature to keep the entropy fixed -see Refs. [6,44] for more discussion. In Fig.…”

“…When the star emits enough radiation, its mass decreases and its temperature drops to a point where matter becomes neutrino transparent and continues cooling till it catalyzes into a cold neutron star [5]. The neutrino signature at the later stages of the evolution is determined by microscopic properties such as the EoS and its composition, neutrino opacity, and other microphysical properties that impact neutrino diffusion and finite entropy systems [6][7][8][9]. The study of gravitational collapse and supernova explosions are essential astrophysical events due to their rich physics and diversity.…”

“…Studies on PNS at finite temperature and fixed entropy considering heavy baryons have also been done in [6,22]. At the same time, hadron-quark phase PNS is also studied in [23] under fixed entropy conditions.…”