Differentiating between sharp and smoother phase transitions in neutron stars

Abstract

The internal composition of neutron stars is still an open issue in astrophysics. Their innermost regions are impervious to light propagation and gravitational waves mostly carry global aspects of stars, meaning that only indirect inferences of their interiors could be obtained. Here we assume a hypothetical future scenario in which an equation of state softening due to a phase transition is identified and estimate the observational accuracy to differentiate a sharp phase transition from a smoother one (associated with a mixed phase/state due to the unknown value of the surface tension of dense matter) in a region of a hybrid star by means of some electromagnetic and gravitational wave observables. We show that different transition constructions lead to similar sequences of stellar configurations due to their shared thermodynamic properties. In the most optimistic case - a strong quark-hadron density jump phase transition - radius observations require fractional uncertainties smaller than $1\%-2\%$ to differentiate mixed states from sharp phase transitions. For tidal deformabilities, relative uncertainties should be smaller than $5\%-10\%$. However, for masses around the onset of stable quark cores, relative tidal deformability differences associated with strong sharp phase transitions and mixed states could be much larger (up to around $20\%-30\%$). All the above suggests that 2.5- and 3rd generation gravitational wave detectors and near-term electromagnetic missions may be able to start assessing some particular aspects of phase transitions in neutron stars. In addition, it points to some limitations on the equation of state recovery using typical neutron star observables and the impact of systematic uncertainties on modellings of the equation of state of hybrid stars. Finally, we briefly discuss other observables that may also be relevant for the probe of mixed states in stars.

17 pages, 15 figures (some updated); Improved abstract, presentation and discussions (assumptions, phase transitions, EOS recovery, predictions, etc); New references added; Accepted for publication in PRD

References in corpus (30)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Advanced Virgo: a 2nd generation interferometric gravitational wave detector
• Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A
• Advanced LIGO
• PSR J0030+0451 Mass and Radius from NICER Data and Implications for the Properties of Neutron Star Matter
• A NICER View of PSR J0030+0451: Millisecond Pulsar Parameter Estimation
• Color superconductivity in dense quark matter
• Tidal Love numbers of neutron stars
• Constraining neutron star tidal Love numbers with gravitational wave detectors
• A NICER View of the Massive Pulsar PSR J0740+6620 Informed by Radio Timing and XMM-Newton Spectroscopy
• Implications of PREX-II on the equation of state of neutron-rich matter
• Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR
• Maximum elastic deformations of compact stars with exotic equations of state
• Compact stars with sequential QCD phase transitions
• Studying strong phase transitions in neutron stars with gravitational waves
• Was GW170817 a canonical neutron star merger? Bayesian analysis with a third family of compact stars
• Phase transitions in neutron stars and their links to gravitational waves
• Constraints on the maximum mass of neutron stars with a quark core from GW170817 and NICER PSR J0030+0451 data
• Bayesian inference of dense matter EOS encapsulating a first-order hadron-quark phase transition from observables of canonical neutron stars
• Search for continuous gravitational waves from 20 accreting millisecond X-ray pulsars in O3 LIGO data
• Uncertainty limits on neutron star radius measurements with gravitational waves
• Phase transitions in rotating neutron stars cores: back bending, stability, corequakes and pulsar timing
• Tidal deformations of hybrid stars with sharp phase transitions and elastic crusts
• Results from high-frequency all-sky search for continuous gravitational waves from small-ellipticity sources
• The Radius of PSR J0740+6620 from NICER and XMM-Newton Data
• Constraint on phase transition with the multimessenger data of neutron stars
• Parameter estimation for strong phase transitions in supranuclear matter using gravitational-wave astronomy
• Probing elastic quark phases in hybrid stars with radius measurements
• Phase Transitions in Neutron Stars
• Strong first-order phase transition in a rotating neutron star core and the associated energy release