Direct URCA process in neutron stars

The onset of the most powerful neutrino emission candidate in the cooling of neutron stars, direct URCA process, requires a high threshold proton fraction. The proton fraction in neutron stars relies on the isospin dependent part of nuclear force, which can be constrained by the measurement of the neutron skin thickness in heavy nuclei such as ²⁰⁸Pb. Adding new isospin dependent correction terms to the effective interactions PK1, NL3, S271 and Z271, the correlation between the proton fraction and neutron skin thickness in ²⁰⁸Pb is studied. For a neutron star with fixed mass, the central proton fraction increases with increasing predicted values of neutron skin thickness in ²⁰⁸Pb.