Constraints of the maximum mass of quark stars based on post-merger evolutions

TL;DR

This paper investigates the post-merger evolution of binary quark star mergers, deriving constraints on the maximum mass of quark stars based on gravitational wave, neutrino emissions, and energy dissipation mechanisms, with implications for GW170817.

Contribution

It provides a semi-analytical framework to estimate post-merger evolution and constrains the maximum mass of cold, non-rotating quark stars using multi-messenger observational data.

Findings

A remnant quark star with mass below the maximum can collapse before losing all rotational energy.

The maximum mass of cold, non-rotating quark stars is constrained to be less than approximately 2.35 solar masses.

Future observations can refine these constraints with better data on post-merger emissions.

Abstract

We semi-analytically investigate the post-merger evolution of the binary quark star merger. The effective-one-body method is employed to estimate the energy and angular momentum dissipation due to gravitational waves in the inspiral phase. Three major mechanisms of energy and angular momentum dissipation are considered in the post-merger phase: mass outflows, neutrinos, and gravitational waves. The proportion of each mechanism could be determined by baryon number, energy and angular momentum conservation laws as well as the equilibrium model for rotating quark stars. Applying this analysis to the GW170817 event suggests two important conclusions: 1) a remnant quark star whose mass is smaller than the maximum mass of a uniformly rotating quark star can collapse before its rotational energy is dissipated via electromagnetic radiation (i.e., $\sim 100\,\mathrm{s}$) as the angular momentum left in the remnant quark star might not be large enough to sustain the additional self-gravity of the supramassive quark star due to the angular momentum dissipation of mass outflows, neutrinos and gravitational waves; 2) considering a general quark star equation of state model, a constraint on the maximum mass of cold and non-rotating quark stars is found as $M_{\mathrm{TOV}}\lesssim2.35^{+0.07}_{-0.17}\,M_{\odot}$, assuming a delayed collapse occurred before a large fraction of the total rotational energy ($\color{blue} \gtrsim 10^{53}\,$erg) of the merger remnant was deposited into the merger environment for the GW170817 event. These constraints could be improved with future merger events, once there are more evidences on its post-merger evolution channel or information on the amount of post-merger gravitational wave and neutrino emissions inferred from the multi-messenger observations.