Cooling of neutron stars and hybrid stars with a stiff hadronic EoS (original) (raw)

Within the "nuclear medium cooling" scenario of neutron stars all reliably known temperature-age data, including those of the central compact objects in the supernova remnants of Cassiopeia A and XMMU-J1732, can be comfortably explained by a set of cooling curves obtained by variation of the star mass within the range of typical observed masses. The recent measurements of the high masses of the pulsars PSR J1614-2230 and PSR J0348-0432 on the one hand, and of the low masses for PSR J0737-3039B and the companion of PSR J1756-2251 on the other, provide independent proof for the existence of neutron stars with masses in a broad range from ∼ 1.2 to 2 M. The values M > 2 M call for sufficiently stiff equations of state for neutron star matter. We investigate the response of the set of neutron star cooling curves to a stiffening of the nuclear equation of state so that maximum masses of about 2.4 M would be accessible and to a deconfinement phase transition from such stiff nuclear matter in the outer core to colour superconducting quark matter in the inner core. Without a readjustment of cooling inputs the mass range required to cover all cooling data for the stiff DD2 equation of state should include masses of 2.426 M for describing the fast cooling of CasA while the existence of a quark matter core accelerates the cooling so that CasA cooling data are described with a hybrid star of mass 1.674 M .