Hot neutron stars with microscopic equations of state

We study the properties of hot $\beta$-stable nuclear matter using equations of state derived within the Brueckner-Hartree-Fock approach at finite temperature including consistent three-body forces. Simple and accurate parametrizations of the finite-temperature equations of state are provided. The adiabatic index is analyzed in some detail. The properties of hot neutron stars are then investigated within this framework, in particular, the temperature dependence of the maximum mass. We find very small temperature effects and analyze the interplay of the different contributions.

Figure 1

Free energy per nucleon as a function of nucleon density for symmetric (lower panels) and pure neutron (upper panels) matter with different EOSs for temperatures ranging from 0 to 50 MeV in steps of 10 MeV (curves decreasing with increasing temperature).

Figure 2

Proton fractions in $\beta$-stable matter at the temperatures $T=0$ (solid curves) and 50 MeV (dashed curves) for the different EOSs.

Figure 3

Internal energy density $\varepsilon$ (solid curves) and pressure $p$ (dashed curves) of $\beta$-stable matter at $T=0$ (upper panel) and changes of those quantities at $T=50\mathrm{MeV}$ for the different EOSs (lower panel).

Figure 4

Lepton and nucleon contributions to the thermal internal energy density of $\beta$-stable matter at $T=50\mathrm{MeV}$ for the different EOSs. The solid (dashed) curves employ the particle fractions of cold (hot) matter, see Fig. 2.

Figure 5

Adiabatic index of $\beta$-stable matter at $T=10,30$, and 50 MeV obtained for different EOSs. The markers indicate the central densities of the maximum-mass stars. For this comparison with RMF results, (anti)muons have been disregarded in the stellar composition. The SNM and PNM results (no leptons) of Ref. [66] are also shown for comparison (dotted curves).

Figure 6

Neutron star gravitational mass vs central density relations at $T=0$, 10, 30, and 50 MeV for the different EOSs.

Figure 7

Temperature dependence of the neutron star gravitational (upper panel) and baryonic (lower panel) maximum mass for the different EOSs.