Speaker
Description
Over 15 years after their discovery, the nature of fast radio burst (FRB) sources still eludes our understanding. To date their bright, coherent radio emission has no detected counterparts outside of the radio band, with the exception of the FRB-like flares emitted by the galactic magnetar SGR 1935+215. These lended support, among the countless proposed interpretations, to the idea that FRB sources may be related to a cosmic population of magnetars. I will summarize the main scenarios that have been devised for explaining the peculiarity of FRB emission, and then introduce our novel interpretation of FRB properties in terms of strong gravitational self-lensing of flares occurring in neutron star (NS) magnetospheres, i.e. flares being lensed by the gravitational field of the NS producing them. I show how this idea explains in a unified picture the large FRB luminosities, the co-existence of rare repeaters and more numerous one-off sources, and their overall energy budget, allowing at the same time to bridge the gap between the apparent paucity of FRBs in the local universe and their comparatively large all-sky rate. Moreover, this interpretation accounts for (a) the double-peaked energy distribution of individual FRBs observed in the most active repeaters, in terms of an emission geometry reminiscent of that typical of radio pulsars, and (b) the redshift (and fluence) distribution of FRBs in the first CHIME catalog, in terms of a dominant population – consistent with magnetars - following the cosmic star formation history.
