Cooling of compact stars with color superconducting phase in quark-hadron mixed phase

Noda, Tsuneo*; Hashimoto, Masaaki*; Yasutake, Nobutoshi*; Maruyama, Toshiki  ; Tatsumi, Toshitaka*; Fujimoto, Masayuki*

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 , 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 not be explained by the minimal cooling scenario with the neutrino emission by nucleon superfluidity (PBF). Then we invoke the exotic cooling processes where heavier stars cool faster than lighter ones. However, the result is inconsistent with the observation of Cas A. Therefore, we present a new cooling scenario by constructing models that include a quark color superconducting (CSC) phase with a large energy gap; this phase appears at ultrahigh density regions and reduces neutrino emissivity. In our model, a compact star has a CSC quark core with a low neutrino emissivity surrounded by high emissivity region made by normal quarks. Our result without considering nucleon superfluidity, shows that while heavier stars cool slowly and lighter ones quickly. 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.