Finite-temperature Extension for Cold Neutron Star Equations of State

Carolyn A. Raithel, Feryal Ozel, Dimitrios Psaltis

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Observations of isolated neutron stars place constraints on the equation of state (EOS) of cold, neutron-rich matter, while nuclear physics experiments probe the EOS of hot, symmetric matter. Many dynamical phenomena, such as core-collapse supernovae, the formation and cooling of proto-neutron stars, and neutron star mergers, lie between these two regimes and depend on the EOS at finite temperatures for matter with varying proton fractions. In this paper, we introduce a new framework to accurately calculate the thermal pressure of neutron-proton-electron matter at arbitrary density, temperature, and proton fraction. This framework can be expressed using a set of five physically motivated parameters that span a narrow range of values for realistic EOS and are able to capture the leading-order effects of degenerate matter on the thermal pressure. We base two of these parameters on a new approximation of the Dirac effective mass, with which we reproduce the thermal pressure to within ≲30% for a variety of realistic EOS at densities of interest. Three additional parameters, which are based on the behavior of the symmetry energy near the nuclear saturation density, allow us to extrapolate any cold EOS in β-equilibrium to arbitrary proton fractions. Our model thus allows a user to extend any cold nucleonic EOS, including piecewise polytropes, to arbitrary temperature and proton fraction for use in calculations and numerical simulations of astrophysical phenomena. We find that our formalism is able to reproduce realistic finite-temperature EOS with errors of ≲20% and offers a 1-3 orders-of-magnitude improvement over existing ideal-fluid models.

Original languageEnglish (US)
Article number12
JournalAstrophysical Journal
Volume875
Issue number1
DOIs
StatePublished - Apr 10 2019

Fingerprint

cold neutrons
equation of state
neutron stars
equations of state
temperature
protons
degenerate matter
nucleonics
ideal fluids
cold
nuclear physics
merger
symmetry
supernovae
astrophysics
probe
saturation
formalism
cooling
neutrons

Keywords

  • Equation of state
  • gravitational waves
  • stars: Neutron
  • supernovae: General

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Finite-temperature Extension for Cold Neutron Star Equations of State. / Raithel, Carolyn A.; Ozel, Feryal; Psaltis, Dimitrios.

In: Astrophysical Journal, Vol. 875, No. 1, 12, 10.04.2019.

Research output: Contribution to journalArticle

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