A Binary Origin for Ultralong-period Radio Pulsars

We propose a possible binary evolution model for the formation of ultralong-period pulsars. The model involves two key stages: first, a neutron star (NS) in wide binaries undergoes an effective spin-down phase through wind-fed accretion from its massive stellar companion; second, the supernova explosion of the companion leads to the disruption of the binary system and produces two isolated compact stars. One of the them is the first-born, slowly rotating NS, and our binary and spin evolution calculations show that the spin periods range from ≲0.1 to ≳108 s. This offers a possible formation channel for some of the long-period radio transients. We estimate that the formation rate of such systems in the Milky Way is approximately 10−6 yr−1.