2004/11/22 by H. Grigorian, Hovik Grigorian, David Blaschke +3 · 15 citations
Earth and Planetary Sciences · Physics and Astronomy · #Geophysics and Gravity Measurements #High-pressure geophysics and materials #Pulsars and Gravitational Waves Research #astro-ph #hep-ph #nucl-th
paper · pdf · doi:10.1103/physrevc.71.045801
published as Phys.Rev. C71 (2005) 045801 · 19 pages, 8 figures
arxiv created 2004/11/22 · openalex publication_date 2005/04/05 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We show that within a recently developed nonlocal, chiral quark model the critical density for a phase transition to color superconducting quark matter under neutron star conditions can be low enough for these phases to occur in compact star configurations with masses below 1.3\phantom\rule0.3em0exM_\ensuremath\bigodot. We study the cooling of these objects in isolation for different values of the gravitational mass. Our equation of state (EoS) allows for two-flavor color superconductivity (2SC) quark matter with a large quark gap (~100\phantom\rule0.3em0exMeV) for u and d quarks of two colors that coexists with normal quark matter within a mixed phase in the hybrid star interior. We argue that, if the phases with unpaired quarks were allowed, the corresponding hybrid stars would cool too fast. If they occurred for M<1.3\phantom\rule0.3em0exM_\ensuremath\bigodot, as follows from our EoS, one could not appropriately describe the neutron star cooling data existing today. We discuss a ``2SC+X'' phase as a possibility for having all quarks paired in two-flavor quark matter under neutron star constraints, where the X gap is of the order of 10\phantom\rule0.3em0exkeV--1\phantom\rule0.3em0exMeV. Density-independent gaps do not allow us to fit the cooling data. Only the presence of an X gap that decreases with increasing density would allow us to appropriately fit the data in a similar compact star mass interval to that following from a purely hadronic model. This scenario is suggested as an alternative explanation of the cooling data in the framework of a hybrid star model.