Early accretion onset in long-period isolated pulsars

Abstract We model long-term magneto-rotational evolution of isolated neutron stars (INSs) with long initial spin periods. This analysis is motivated by the recent discovery of young long-period neutron stars (NSs) observed as periodic radio sources: PSR J0901-4046, GLEAM-X J1627-52, and GPM J1839-10. Our calculations demonstrate that for realistically rapid spin-down during the propeller stage INSs with velocities ${\lesssim}100$ km s $^{-1}$ and assumed long initial spin periods can reach the stage of accretion from the interstellar medium within at most a few billion years as they are born already at the propeller stage or sufficiently close to the critical period of the ejector-propeller transition. If NSs with long initial spin periods form a relatively large fraction of all Galactic NSs then the number of isolated accretors is substantially larger than it has been predicted by previous studies.