A model of neutron star -- white dwarf collision for fast radio bursts

Abstract

Fast radio bursts (FRBs) with unknown origin emit a huge luminosity (about 1 Jy at 1 GHz) in duration of milliseconds or less, at extragalactic distances estimated from their large dispersion measure (DM). We propose a neutron star (NS) and a white dwarf (WD) collision scenario as the progenitor of the FRBs, by considering with the burst duration equaling to the collision time and the radio luminosity proportional to the kinetic energy of the collision. The relations among the observed flux density, pulse width and the DM are derived from the model, and compared with the statistical results from the observed 28 FRBs. Although the sample is quite small, we tentatively find that the observed peak flux density is inverse-squared correlated with the DM excess which assumed to be dominating by the intergalactic medium (IGM), and it also implies a narrower distribution of intrinsic pulse widths than that of observed widths for the FRBs. Shorter burst is expected to be brighter in the model. The NS-WD collision scenario could explain only for the non-repeating FRBs, but if the remnant of the merger is a magnetized pulsar, which might be also capable to account for the repeating FRB.