# A new temperature dependent hyperonic equation of state: application to rotating neutron star models and I-Q-relations

## TL;DR

This paper introduces a new temperature-dependent hyperonic equation of state for neutron stars, explores its implications for rotating models, and examines the universality of I-Q relations at nonzero temperatures, highlighting limitations for astrophysical applications.

## Contribution

The paper presents a novel hyperonic EoS compatible with nuclear physics constraints and investigates the impact of temperature on I-Q relation universality in rotating neutron stars.

## Key findings

- The new EoS supports neutron star masses up to 2 solar masses.
- Thermal effects break I-Q universality in hot, rotating neutron stars.
- Using I-Q relations in hot neutron star analysis requires caution.

## Abstract

In this work we present a newly constructed equation of state (EoS) --applicable to stellar core collapse and neutron star mergers--, including the entire baryon octet. Our EoS is compatible with the main constraints from nuclear physics and, in particular, with a maximum mass for cold beta-equilibrated neutron stars of 2 solar masses in agreement with recent observations. As an application of our new EoS, we compute numerical stationary models for rapidly (rigidly) rotating hot neutron stars. We consider maximum masses of hot stars, such as proto-neutron stars or hypermassive neutron stars in the post-merger phase of binary neutron star coalescence. The universality of I-Q-relations at nonzero temperature for fast rotating models, comparing a purely nuclear EoS with its counterparts containing Lambda-hyperons or the entire baryon octet, respectively, is discussed, too. We find that the I-Q universality is broken when thermal effects become important, whatever the value of entropy gradients in our models. Thus, the use of I-Q relations for the analysis of proto-neutron stars or merger remnant data, including gravitational wave signals from the last stages of binary neutron star mergers, should be regarded with care.