Locating the special point of hybrid neutron stars

Abstract

The special point is a feature unique to models of hybrid neutron stars. It represents a location on their mass--radius sequences that is insensitive to the phase transition density. We consider hybrid neutron stars with a core of deconfined quark matter that obeys a constant--sound--speed (CSS) equation of state model and provide a fit formula for the coordinates of the special point as functions of the squared sound speed ($c_s^2$) and pressure scale ($A$) parameters. Using the special point mass as a proxy for the maximum mass of the hybrid stars we derive limits for the CSS model parameters based on the recent NICER constraint on mass and radius of pulsar PSR J0740+6620, $0.36<{c_s^2}_{\min }<0.43$ and $80<A[{MeV/fm}^3]<160$. The upper limit for the maximum mass of hybrid stars depends on the upper limit for $c_s^2$ so that choosing $c_{s,max}^2=0.6$ results in $M_{\max }<2.7M_{\odot }$, within the mass range of GW190814.

8 pages, 5 figures, 1 table

References in corpus (9)

• Shapiro delay measurement of a two solar mass neutron star
• Neutron-star radius constraints from GW170817 and future detections
• Constraints on Neutron Star Properties from X-ray Observations of Millisecond Pulsars
• Was GW170817 a canonical neutron star merger? Bayesian analysis with a third family of compact stars
• Studying the onset of deconfinement with multi-messenger astronomy of neutron stars
• Neutron-star radii based on realistic nuclear interactions
• The special point on the hybrid star mass--radius diagram and its multi--messenger implications
• Hybrid neutron stars in the mass-radius diagram
• Special point on the mass radius diagram of hybrid stars

Cited by in corpus (7)

• Quark-nuclear hybrid equation of state for neutron stars under modern observational constraints
• Recovering the conformal limit of color superconducting quark matter within a confining density functional approach
• Hybrid star phenomenology from the properties of the special point
• Implications of supermassive neutron stars for the form of the equation of state of hybrid stars
• Special point "trains" in the M-R diagram of hybrid stars
• Compact Star Twins with a Dark Matter Core
• Density functional approach to quark matter with confinement and color superconductivity