The researchers in the Theoretical Physics Group at Institute of Modern Physics (IMP), Chinese Academy of Sciences，have investigated the neutron star cooling affected by the nucleonic Fermi surface depletion.
Neutron star cooling is a hot topic that connects nuclear physics and astrophysics. Nowadays, the measurements on the neutron star surface temperature such as Cas A allow human beings to investigate the thermal evolution of NSs more deeply and hence grasp some crucial information and knowledge on the NS interior as well as some properties of dense nuclear matter. The Fermi surface depletion that comes from the nucleonic short-range correlation influences the level density of nucleons around the Fermi surface and controls many properties of Fermion systems related to particle-hole excitations around the Fermi energy. Thus, it affects the inputs of the neutron star cooling .
The Fermi surface depletion of beta-stable nuclear matter was calculated and its effects on several physical properties which determine the neutron star thermal evolution were investigated. The conclusion are summarized as follows: 1) The Fermi surface depletion quenches the peak value of 3PF2 superfluidity by about one order of magnitude, and its effect is extremely strong at high densities. 2) The kinematic conditions giving rise to the threshold for the DU process do not change, and the neutrino emissivity for the DU process is reduced which is in complete contrast to previous expectations. In addition, the neutrino emissivity for the MU processes, the nucleon-nucleon bremsstrahlung processes, the Cooper pair breaking and formation processes are also reduced. 3) The heat capacity of beta-stable neutron star matter is reduced. 4) The cooling rates of young neutron stars are significantly slowed. The effect of the Fermi surface depletion of nucleons on NS cooling cannot be neglected, when an accurate theoretical study of the cooling is performed.
The work has been published in Astrophysical Journal, 817, 6 (2016).
The article can be linked as follows:http://iopscience.iop.org/article/10.3847/0004-637X/817/1/6
Fig. 1 Cooling curves of a canonical neutron star. (Image by IMP)