By considering the expression for the total neutrino luminosity, Lν, in terms of the neutrino total emissivity and the volume of a neutron star, we confirm that indeed the luminosity for the direct URCA processes has a dependence on temperature of order T6 as assumed by Heinke and Ho. However, as can be seen in our formulation, Lν depends also on a variety of ingredients that characterize properties of dense nuclear matter as baryon effective masses, Fermi momenta and energy, as well as parameters that characterize the weak interaction beta process. In particular, the dependence of the luminosity of neutrinos in the effective mass of baryons that make up a neutron star opens a new perspective on the study of properties of dense nuclear matter. The model adopted in our calculations may represent, we believe, a further step in elucidating the mysteries surrounding the cooling of Cassiopeia A. Work along this line is in progress
A neutron star with a carbon atmosphere in the Cassiopeia A supernova remnant
