Cooling of Neutron Stars: Two Types of Triplet Neutron Pairing

We consider cooling of neutron stars (NSs) with superfluid cores composed of neutrons, protons, and electrons (assuming singlet-state pairing of protons, and triplet-state pairing of neutrons). We mainly focus on (nonstandard) triplet-state pairing of neutrons with the |mJ | = 2 projection of the total angular momentum of Cooper pairs onto quantization axis. The specific feature of this pairing is that it leads to a power-law (nonexponential) reduction of the emissivity of the main neutrino processes by neutron superfluidity. For a wide range of neutron critical temperatures Tcn, the cooling of NSs with the |mJ | = 2 superfluidity is either the same as the cooling with the mJ = 0 superfluidity, considered in the majority of papers, or much faster. The cooling of NSs with density dependent critical temperatures Tcn(ρ) and Tcp(ρ) can be imitated by the cooling of the NSs with some effective critical temperatures Tcn and Tcp constant over NS cores. The hypothesis of strong neutron superfluidity with |mJ | = 2 is inconsistent with current observations of thermal emission from NSs, but the hypothesis of weak neutron superfluidity of any type does not contradict to observations.