Volume 528, April 2011
|Number of page(s)||10|
|Section||Stellar structure and evolution|
|Published online||03 March 2011|
Effects of quark matter nucleation on the evolution of proto-neutron stars
1 Dipartimento di Fisica “E.
Fermi”Università di Pisa, Largo B.
Pontecorvo 3, 56127 Pisa, Italy
2 INFN, Sezione di Pisa, Largo B. Pontecorvo 3, 56127 Pisa, Italy
3 Centro de Física Computacional, Department of Physics, University of Coimbra, 3004-516 Coimbra, Portugal
Received: 18 September 2010
Accepted: 3 December 2010
Context. A phase of strong interacting matter with deconfined quarks is expected in the core of a massive neutron star. If this deconfinement phase transition is of the first order, as suggested by many models inspired by quantum chromodynamics, then it will be triggered by the nucleation of a critical size drop of the (stable) quark phase in the metastable hadronic phase. Within these circumstances it has been shown that cold (T = 0) pure hadronic compact stars above a threshold value of their gravitational mass (central pressure) are metastable with respect to the “decay” (conversion) to quark stars (i.e., compact stars made at least in part of quark matter). This stellar conversion process liberates a huge amount of energy (a few 1053 erg), and it could be the energy source of some of the long gamma ray bursts.
Aims. The main goal of the present work is to establish whether a newborn hadronic star (proto-hadronic star) could survive the early stages of its evolution without “decaying” to a quark star. To this aim, we study the nucleation process of quark matter in hot (T ≠ 0) β-stable hadronic matter, with and without trapped neutrinos, using a finite temperature equation of state (EOS) for hadronic and quark matter.
Methods. The finite-temperature EOS for the hadronic and for the quark phases were calculated using the nonlinear Walecka model and the MIT bag model, respectively. The quantum nucleation rate was calculated making use of the Lifshitz & Kagan nucleation theory. The thermal nucleation rate was calculated using the Langer nucleation theory.
Results. We calculate and compare the nucleation rate and the nucleation time due to thermal and quantum nucleation mechanisms. We compute the crossover temperature above which thermal nucleation dominates the finite temperature quantum nucleation mechanism. We next discuss the consequences of quark matter nucleation for the physics and the evolution of proto-neutron stars. We introduce the new concept of limiting conversion temperature and critical mass Mcr for proto-hadronic stars, and we show that proto-hadronic stars with a mass M < Mcr could survive the early stages of their evolution without decaying to a quark star. We extend the concept of maximum mass of a “neutron star” with respect to the classical one introduced by Oppenheimer & Volkoff to account for the existence of two distinct families of compact stars (hadronic stars and quark stars) as predicted by the present scenario.
Key words: dense matter / equation of state / stars: neutron
© ESO, 2011
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