Rapidly rotating $\Delta$-resonance-admixed hypernuclear compact stars

TL;DR

This study investigates how the high-density behavior of equations of state affects the properties of rapidly rotating hypernuclear compact stars with $$-resonance admixture, suggesting such stars are unlikely to reach 2.5 solar masses under realistic conditions.

Contribution

It systematically analyzes the impact of key nuclear matter parameters on the maximum mass of rotating hypernuclear stars with $$-resonance, highlighting the extreme conditions needed for very massive stars.

Findings

Maximum mass around 2.5 solar masses requires specific conditions.

Large $Q_{sat}$ and small $L_{sym}$ are incompatible with most models.

Implication that GW190814's secondary is likely a black hole.

Abstract

We use a set of hadronic equations of state derived from covariant density functional theory to study the impact of their high-density behavior on the properties of rapidly rotating $\Delta$-resonance-admixed hyperonic compact stars. In particular, we explore systematically the effects of variations of the bulk energy isoscalar skewness, $Q_{\mathrm{sat}}$, and the symmetry energy slope, $L_{\mathrm{sym}}$, on the masses of rapidly rotating compact stars. With models for equation of state satisfying all the modern astrophysical constraints, excessively large gravitational masses of around $2.5 \, M_{\odot}$ are only obtained under three conditions: (a) strongly attractive $\Delta$-resonance potential in nuclear matter, (b) maximally fast (Keplerian) rotation, and (c) parameter ranges $Q_{\mathrm{sat}}\gtrsim500$ MeV and $L_{\mathrm{sym}}\lesssim50$ MeV. These values of $Q_{\mathrm{sat}}$ and $L_{\mathrm{sym}}$ have a rather small overlap with a large sample (total of about 260) parametrizations of covariant nucleonic density functionals. The extreme nature of requirements (a)-(c) reinforces the theoretical expectation that the secondary object involved in the GW190814 event is likely to be a low-mass black hole rather than a supramassive neutron star.