Publications (3)0 Total impact
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Article: Cooling of Compact Stars with Color Superconducting Phase in Quark Hadron Mixed Phase
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ABSTRACT: We present a new scenario for the cooling of compact stars considering the central source of Cassiopeia A (Cas A). The Cas A observation shows that the central source is a compact star that has high effective temperature, and it is consistent with the cooling without exotic phases. The observation also gives the mass range of $M \geqslant 1.5 M_\odot$, which may conflict with the current plausible cooling scenario of compact stars. There are some cooled compact stars such as Vela or 3C58, which can be barely explained by the minimal cooling scenario, which includes the neutrino emission by nucleon superfluidity (PBF). Therefore, we invoke the exotic cooling processes, where a heavier star cools faster than lighter one. However, the scenario seems to be inconsistent with the observation of Cas A. Therefore, we present a new cooling scenario to explain the observation of Cas A by constructing models that include a quark color superconducting (CSC) phase with a large energy gap; this phase appears at ultrahigh density region and reduces neutrino emissivity. In our model, a compact star has CSC quark core with a low neutrino emissivity surrounded by high emissivity region made by normal quarks. We present cooling curves obtained from the evolutionary calculations of compact stars: while heavier stars cool slowly, and lighter ones indicate the opposite tendency without considering nucleon superfluidity. Furthermore, we show that our scenario is consistent with the recent observations of the effective temperature of Cas A during the last 10 years, including nucleon superfluidity.09/2011; -
Article: Cooling of Compact Stars with Quark-Hadron Mixed Phase in the Colour Superconductive State
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ABSTRACT: Recently, the central source of Cassiopeia A (Cas A) has been observed, which indicates that the star has large mass and high effective temperature. We suspect that the compact object cools by the standard neutrino emission. We assume that the compact object contains quark matter with colour superconductivity and calculate cooling curves. Considering the Quark-Hadron Mixed Phase, we obtain cooling curves which are found to be consistent with the observations.AIP Conference Proceedings 08/2010; 1269(1). -
Article: Exotic Cooling on Neutron Stars with Different Surface Compositions
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ABSTRACT: The thermal evolution of isolated neutron stars depends on neutrino emission process, equation of state (EOS) of nuclear matter, and surface composition. Focusing on the neutrino emission process, we can classify the cooling models in two groups. First one is the "standard cooling model", which includes modified URCA process and bremsstrahlung process; these processes are believed to operate inside neutron stars. Others include some exotic processes at high density or high temperature, such as pion condensation or quark beta decay, which is named as "exotic cooling model". Since exotic models result in high neutrino emission, exotic neutron stars cool much faster than standard ones. We investigate the thermal evolution of isolated neutron stars, using both the standard and the exotic cooling processes, and two kinds of surface composition, He and Fe. Furthermore we employ nucleon superfluidity models, and adopt a critical temperature as a density-independent parameter. We find that there exist parameter regions which can be consistent with the observational results.
