Speaker
Description
The physical description of pulsars remains obscure. Although widely modelled as neutron stars, their correct description requires observations that probe their microphysics. Precise measurements of neutron star masses and radii by the NICER mission impose important constraints on the nuclear equation of state. We use state-of-the-art NICER measurements to date, including the most recent NICER measurement of PSR J0614-3329 that reported an equatorial radius of R_{eq} ~ 10.29 km for a mass of M ~ 1.44 M_{\odot}. We consider a wide range of neutron stars and strange quark stars, composed of deconfined quark matter, derived from both realistic phenomenological and microscopic models, and carry out a Bayesian hypothesis ranking analysis to perform model selection. We find substantial evidence for strange quark stars over physically motivated models of neutron stars that are compatible with this low radius, and also find a hint of the hadron-to-quark phase transition inside neutron stars. Using a wide sample of equations of state, we report the nucleonic neutron star equations of state that best fit current observations and rule out one model of strange quark matter. This analysis presents a compelling case for quark matter in neutron stars and also for the possible existence of strange quark stars, a consequence of the Bodmer-Witten hypothesis, which suggests that they could be considered among the population of compact stars during astrophysical data analyses.
