PSR J0614-3329: A NICER case for Strange Quark Stars

TL;DR

This paper uses NICER measurements of PSR J0614-3329 to provide Bayesian evidence favoring strange quark stars over traditional neutron star models, suggesting quark matter may exist in compact stars.

Contribution

It presents the first Bayesian analysis comparing strange quark star models with neutron star models using NICER data, supporting the existence of quark matter in neutron stars.

Findings

Bayesian hypothesis ranking favors strange quark stars.

NICER measurements constrain neutron star radii.

Some strange quark matter models are ruled out.

Abstract

Precise measurements of neutron star masses and radii by the NICER mission impose important constraints on the nuclear equation of state. The most recent NICER measurement of PSR J0614-3329 reported an equatorial radius of $R_{eq} = 10.29^{+1.01}_{-0.86}$ km for a mass of $M = 1.44^{+0.06}_{-0.07} M_{\odot}$. Considering all the NICER measurements to date, we find substantial evidence using Bayesian hypothesis ranking for strange quark stars over physically motivated models of neutron stars compatible with this low radius. This provides a strong case for quark matter in neutron stars and also for the possible existence of strange quark stars, a consequence of the Bodmer-Witten hypothesis, suggesting that they could be considered among the population of compact stars during analyses of astrophysical data. Using a wide sample of equations of state, we report the nucleonic equations of state that best fit current observations and rule out one model of strange quark matter.