Constraints on the maximum mass of neutron stars with a quark core from GW170817 and NICER PSR J0030+0451 data

TL;DR

This paper uses Bayesian analysis of gravitational wave and NICER data to constrain the maximum mass of neutron stars with quark cores, providing bounds that inform astrophysical phenomena and the nature of dense matter.

Contribution

It introduces a Bayesian framework combining GW170817 and NICER data to estimate the maximum mass of hybrid neutron stars with a quark core, considering different hadronic EOS models.

Findings

Most probable maximum mass around 2.36-2.39 solar masses.

Absolute upper bound near 2.85 solar masses.

Results are robust against hadronic EOS uncertainties.

Abstract

We perform a Bayesian analysis of the maximum mass $M_{\rm TOV}$ of neutron stars with a quark core, incorporating the observational data from tidal deformability of the GW170817 binary neutron star merger as detected by LIGO/Virgo and the mass and radius of PSR J0030+0451 as detected by \nicer. The analysis is performed under the assumption that the hadron-quark phase transition is of first order, where the low-density hadronic matter described in a unified manner by the soft QMF or the stiff DD2 equation of state (EOS) transforms into a high-density phase of quark matter modeled by the generic "Constant-sound-speed" (CSS) parameterization. The mass distribution measured for the $2.14 \,{\rm M}_{\odot}$ pulsar, MSP J0740+6620, is used as the lower limit on $M_{\rm TOV}$. We find the most probable values of the hybrid star maximum mass are $M_{\rm TOV}=2.36^{+0.49}_{-0.26}\,{\rm M}_{\odot}$ ($2.39^{+0.47}_{-0.28}\,{\rm M}_{\odot}$) for QMF (DD2), with an absolute upper bound around $2.85\,{\rm M}_{\odot}$, to the $90\%$ posterior credible level. Such results appear robust with respect to the uncertainties in the hadronic EOS. We also discuss astrophysical implications of this result, especially on the post-merger product of GW170817, short gamma-ray bursts, and other likely binary neutron star mergers.