New Bayesian analysis of hybrid EoS constraints with mass-radius data for compact stars
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ew Bayesian Analysis of Hybrid EoS Constraints with MassRadius Data for Compact Stars1 A. Ayriyana, D. E. AlvarezCastillob, c, D. Blaschkeb, d, H. Grigoriana, e, and M. Sokolowskid a
Laboratory of Information Technologies, JINR Dubna, Russia Bogoliubov Laboratory of Theoretical Physics, JINR Dubna, Russia c Instituto de Física, Universidad Autónoma de San Luis Potosí, México d Institute of Theoretical Physics, University of Wroclaw, Poland eDepartment of Physics, Yerevan State University, Armenia email: [email protected] b
Abstract—We suggest a new Bayesian analysis using disjunct mass and radius constraints for extracting prob ability measures for cold, dense nuclear matter equations of state. One of the key issues of such an analysis is the question of a deconfinement transition in compact stars and whether it proceeds as a crossover or rather as a first order transition. The latter question is relevant for the possible existence of a critical endpoint in the QCD phase diagram under scrutiny in present and upcoming heavyion collision experiments. DOI: 10.1134/S1063779615050044 1
1. INTRODUCTION
The most basic features of a neutron star (NS) are the radius R and the mass M which so far have not been well determined simultaneously for a single object. In some cases masses are precisely measured like in the case of binary systems, but radii are quite uncertain [1]. In the other hand, for isolated neutron stars some radius and mass measurements exist but lack the nec essary precision to allow conclusions about their inte riors. In fact, it has been conjectured that there exists a unique relation between M and R for all neutron stars and their equation of state (EoS), thus constraining the properties of their interior [2]. For this reason, accurate observations of masses and radii are crucial to study cold dense nuclear matter expected to exist in neutron stars. However, the presently observational data allow to make only a probabilistic estimations of the internal structure of the star, via Bayesian analysis (BA). This technique has been applied for the first time to this problem by Steiner et al. [3] who exemplified very well the power of this method. In their analysis, how ever, only a particular type of objects (Xray bursters) has been considered under strongly model dependent assumptions. In this work is a continuation of our preliminary probabilistic studies of the superdense stellar matter equation of state using Bayesian Anal ysis and modeling of relativistic configurations of neutron stars [4, 5]. We put special emphasis on the choice of observational constraints and focus on investigations of the possible existence of deconfined quark matter in massive neutron stars such as the recently observed 2 M䉺 pulsars [6, 7]. 1 The article is published in the original.
2. NS STRUCTURE AND EoS The microscopical properties of compact stars are modeled in the framework of general relativity, where the Einstein equations are solved for a static (non rotating), spherical star resulting in the Tolman– Oppenheim
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