Eur. Phys. J. A (2016) 52: 69
https://doi.org/10.1140/epja/i2016-16069-2

Regular Article - Theoretical Physics

New class of hybrid EoS and Bayesian M - R data analysis

¹ Bogoliubov Laboratory of Theoretical Physics, JINR Dubna, Dubna, Russia
² Laboratory of Information Technologies, JINR Dubna, Dubna, Russia
³ Department of Physics, University of Zagreb, Zagreb, Croatia
⁴ National Research Nuclear University (MEPhI), Moscow, Russia
⁵ GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany

^* e-mail: alexander.ayriyan@gmail.com

Received: 8 March 2016
Accepted: 10 March 2016
Published online: 28 March 2016

Abstract

We explore systematically a new class of two-phase equations of state (EoS) for hybrid stars that is characterized by three main features: 1) stiffening of the nuclear EoS at supersaturation densities due to quark exchange effects (Pauli blocking) between hadrons, modelled by an excluded volume correction; 2) stiffening of the quark matter EoS at high densities due to multiquark interactions; and 3) possibility for a strong first-order phase transition with an early onset and large density jump. The third feature results from a Maxwell construction for the possible transition from the nuclear to a quark matter phase and its properties depend on the two parameters used for 1) and 2), respectively. Varying these two parameters, one obtains a class of hybrid EoS that yields solutions of the Tolman-Oppenheimer-Volkoff (TOV) equations for sequences of hadronic and hybrid stars in the mass-radius diagram which cover the full range of patterns according to the Alford-Han-Prakash classification following which a hybrid star branch can be either absent, connected or disconnected with the hadronic one. The latter case often includes a tiny connected branch. The disconnected hybrid star branch, also called “third family”, corresponds to high-mass twin stars characterized by the same gravitational mass but different radii. We perform a Bayesian analysis and demonstrate that the observation of such a pair of high-mass twin stars would have a sufficient discriminating power to favor hybrid EoS with a strong first-order phase transition over alternative EoS.