On ultra-long period (53.8 min) pulsar ASKAP J1935+2148: coherent radio emission triggered by local superstrong magnetic reconnection

The eight ultra-long period pulsars (ULPPs) in radio bands have been discovered recently, e.g., ASKAP J1935+2148 with a spin period of 53.8 min, which are much longer than those of normal pulsars, spanning from 0.016 s to 23.5 s, however the origins, spin evolutions and emission mechanisms of these sources are still puzzling. We investigate how the ultra-long period of ASKAP J1935+2148 is evolved by the braking of relativistic particle wind, in a time scale of about 0.1 - 1 Myr, from a normal pulsar with local superstrong magnetic fields. In addition, it is noticed that the ULPPs in the period versus period derivative diagram are much below the “death line”, implying their different characteristics from the normal pulsars. Five sources (including ASKAP J1935+2148) in total eight ULPPs share the rotational energy loss rates to be lower than their respective radio emission luminosities, a phenomenon that can be accounted for by the sustainable radio bursts induced through the reconnection of locally concentrated magnetic field lines. The diversity and complexity of ULPP radio emissions should be closely related to the presence of magnetic reconnection rather than rotational powered discharges in the gaps. Furthermore, it is suggested that the coherent radio emissions of pulsars may have two origins, one from the rotation-powered electric voltage that accounts for the normal pulsar phenomena and the other from the magnetic reconnection-induced continual radio bursts that account for the ULPP observations.