Thermodynamical Description of Hot, Rapidly Rotating Neutron Stars, Protoneutron Stars, and Neutron Star Merger Remnants

TL;DR

This paper develops and analyzes equations of state for hot, dense nuclear matter, focusing on their effects on the structure and properties of hot, rapidly rotating neutron stars and merger remnants, with implications for astrophysical observations.

Contribution

It introduces a self-consistent method to incorporate thermal effects into nuclear equations of state for rotating neutron stars, extending understanding of their structure and observational signatures.

Findings

Thermal effects significantly influence neutron star mass and radius.

Rotation at Kepler frequency alters neutron star properties.

Data can constrain nuclear matter equations of state.

Abstract

The prediction of the equation of state of hot, dense nuclear matter is one of the most complicated and interesting problems in nuclear astrophysics. At the same time, knowledge of it is the basic ingredient for some of the most interesting studies. In the present work, we concentrate our study on the construction of the equation of state of hot, dense nuclear matter, related mainly to the interior of the neutron star. We employ a theoretical nuclear model, which includes momentum-dependent interaction among the nucleons, along with the \textit{state-of-the-art} microscopic calculations. Thermal effects are introduced in a self-consistent way, and a set of isothermal and isentropic equations of state are predicted. The predicted equations of state are used in order to acquire and to extend the knowledge of the thermal effect on both nonrotating and rapidly rotating with the Kepler frequency neutron stars. The simultaneous study of thermal and rotation effects provides useful information on some of the most important quantities, including the mass (gravitational and baryon) and radius, the Kepler frequency and Kerr parameter, the moment of inertia, etc. These quantities are directly related to studies of protoneutron stars and mainly the hot and rapidly rotating remnant of a binary neutron star merger. Data from the late observations of binary neutron star mergers and the present study may offer useful tools for their investigation and help in providing possible constraints on the equation of state of nuclear matter.