Electromagnetic emission from blitzars and its impact on non-repeating fast radio bursts

Abstract

It has been suggested that a non-repeating fast radio burst (FRB) represents the final signal of a magnetized neutron star collapsing to a black hole. In this model, a supramassive neutron star supported by rapid rotation, will collapse to a black hole several thousand to million years after its birth as a result of spin down. The collapse violently snaps the magnetic-field lines anchored on the stellar surface, thus producing an electromagnetic pulse that will propagate outwards and accelerate electrons producing a massive radio burst, i.e. a "blitzar". We present a systematic study of the gravitational collapse of rotating and magnetised neutron stars with special attention to far-field evolution at late times after the collapse. By considering a series of neutron stars with rotation ranging from zero to millisecond periods and different magnetic-field strengths, we show that the blitzar emission is very robust and always characterised by a series sub-millisecond pulses decaying exponentially in amplitude. The luminosity and energy released when the magnetosphere is destroyed are well reproduced by a simple expression in terms of the stellar magnetic field and radius. Finally, we assess the occurrence of pair production during a blitzar scenario, concluding that for typical magnetic-field strengths of $10^{12}\,{\rm G}$ and spin frequencies of a few Hz, pair production is suppressed. Overall, the very good match between the results of the simulations and the luminosities normally observed for FRBs lends credibility to the blitzar model as a simple and yet plausible explanation for the phenomenology of non-repeating FRBs.