Browsing by Author "Guillot, Sebastien"

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    Constraining the equation of state of dense nuclear matter using thermal emission of neutron stars
    (2020) Baillot d’Étivaux, Nicolas; Margueron, Jérôme; Guillot, Sebastien; Webb, Natalie; Catelan, Márcio; Reisenegger, Andreas
    In this work, the equation of state (EoS) of the dense matter in the core of neutron stars (NSs) is based on a recently proposed meta-modeling of nuclear matter composed of nucleons, which can be parametrized by empirical quantities such as the energy density at saturation density or the nuclear incompressibility modulus. We use a set of recent observations of the thermal emission of seven NSs in quiescent low-mass X-ray binaries (qLMXBs) in order to find some constraints on the parameters of the meta-model, and thus on the nuclear EoS. This is done in a Bayesian statistical framework using Markov Chain Monte Carlo (MCMC) methods, to perform a simultaneous analysis over the seven sources. For the first time, the theoretical modeling of the EoS is directly implemented in the data analysis. We obtain constraints on the slope of the symmetry energy, {L}sym={37.2}-8.9+9.2 MeV, and give the first estimation of its curvature, {K}sym=-{85}-70+82 MeV, and on the isoscalar skewness parameter, {Q}sat={318}-366+673 MeV. Radii of about 12 km are preferred with a good fit statistic, yielding a nuclear EoS that is consistent with observational data and recent gravitational waves signals from NSs coalescence....
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    THE DENSE MATTER EQUATION OF STATE FROM NEUTRON STAR RADIUS AND MASS MEASUREMENTS
    (IOP PUBLISHING LTD, 2016) Oezel, Feryal; Psaltis, Dimitrios; Guever, Tolga; Baym, Gordon; Heinke, Craig; Guillot, Sebastien
    We present a comprehensive study of spectroscopic radius measurements of twelve neutron stars obtained during thermonuclear bursts or in quiescence. We incorporate, for the first time, a large number of systematic uncertainties in the measurement of the apparent angular sizes, Eddington fluxes, and distances, in the composition of the interstellar medium, and in the flux calibration of X-ray detectors. We also take into account the results of recent theoretical calculations of rotational effects on neutron star radii, of atmospheric effects on surface spectra, and of relativistic corrections to the Eddington critical flux. We employ Bayesian statistical frameworks to obtain neutron star radii from the spectroscopic measurements as well as to infer the equation of state from the radius measurements. Combining these with the results of experiments in the vicinity of nuclear saturation density and the observations of similar to 2 M-circle dot neutron stars, we place strong and quantitative constraints on the properties of the equation of state between approximate to 2-8 times the nuclear saturation density. We find that around M = 1.5 M-circle dot, the preferred equation of state predicts radii between 10.1 and 11.1 km. When interpreting the pressure constraints in the context of high density equations of state based on interacting nucleons, our results suggest a relatively weak contribution of the three-body interaction potential.