Abstract
Abstract Whether fast cooling processes occur or not is crucial for the thermal evolution of neutron stars. In particular, the threshold of the direct Urca process, which is one of the fast cooling processes, is determined by the interior proton fraction $Y_p$, or the nuclear symmetry energy. Since recent observations indicate the small radius of neutron stars, a low value is preferred for the symmetry energy. In this study, simulations of neutron star cooling are performed adopting three models for the equation of state (EoS): Togashi, Shen, and LS220 EoSs. The Togashi EoS has been recently constructed with realistic nuclear potentials under finite temperature, and found to account for the small radius of neutron stars. As a result, we find that, since the direct Urca process is forbidden, the neutron star cooling is slow with use of the Togashi EoS. This is because the symmetry energy of Togashi EoS is lower than those of other EoSs. Hence, in order to account for observed age and surface temperature of isolated neutron stars with the use of the Togashi EoS, other fast cooling processes are needed regardless of the surface composition.
Highlights
Neutron stars are formed as a remnant of core-collapse supernovae
We present the cooling curves of neutron stars obtained from our calculations with the Togashi equation of state (EoS), Shen EoS, and LS220 EoS in Figs. 4, 5, and 6, respectively
The LS220 EoS can account for the temperature observations of isolated neutron stars (INS) through the direct Urca (DU) process by considering appropriate superfluid model
Summary
Neutron stars are formed as a remnant of core-collapse supernovae. Nascent neutron stars are hot and their temperature decreases with their age. Since the ages of observed neutron stars are mostly younger than 106−7 yr [1], the observed temperature of neutron stars depends mainly on neutrino emission processes. The thermal evolutions of neutron stars are described by cooling curves; the relation between the age t and the effective temperature Te∞ff of neutron stars. The EoS dependence of the cooling curves has been studied actively [12, 13]. Another significant effect on the neutron star cooling comes from the superfluidity [8, 14,15,16]. To calculate cooling curves we adopt models of EoS, neutrino loss rates, and superfluid critical temperature, as indispensable physical quantities
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
