FAST RADIO BURST DISCOVERED IN THE ARECIBO PULSAR ALFA SURVEY

Abstract

Recent work has exploited pulsar survey data to identify temporally isolated,\nmillisecond-duration radio bursts with large dispersion measures (DMs). These\nbursts have been interpreted as arising from a population of extragalactic\nsources, in which case they would provide unprecedented opportunities for\nprobing the intergalactic medium; they may also be linked to new source\nclasses. Until now, however, all so-called fast radio bursts (FRBs) have been\ndetected with the Parkes radio telescope and its 13-beam receiver, casting some\nconcern about the astrophysical nature of these signals. Here we present FRB\n121102, the first FRB discovery from a geographic location other than Parkes.\nFRB 121102 was found in the Galactic anti-center region in the 1.4-GHz Pulsar\nALFA survey with the Arecibo Observatory with a DM = 557.4 $\\pm$ 3 pc\ncm$^{-3}$, pulse width of $3\\; \\pm 0.5$ ms, and no evidence of interstellar\nscattering. The observed delay of the signal arrival time with frequency agrees\nprecisely with the expectation of dispersion through an ionized medium. Despite\nits low Galactic latitude ($b = -0.2^{\\circ}$), the burst has three times the\nmaximum Galactic DM expected along this particular line-of-sight, suggesting an\nextragalactic origin. A peculiar aspect of the signal is an inverted spectrum;\nwe interpret this as a consequence of being detected in a sidelobe of the ALFA\nreceiver. FRB 121102's brightness, duration, and the inferred event rate are\nall consistent with the properties of the previously detected Parkes bursts.\n