A Nearby Repeating Fast Radio Burst in the Direction of M81

We report on the discovery of FRB 20200120E, a repeating fast radio burst (FRB) with a low dispersion measure (DM) detected by the Canadian Hydrogen Intensity Mapping Experiment FRB project. The source DM of 87.82 pc cm(-3) is the lowest recorded from an FRB to date, yet it is significantly higher than the maximum expected from the Milky Way interstellar medium in this direction (similar to 50 pc cm(-3)). We have detected three bursts and one candidate burst from the source over the period 2020 January-November. The baseband voltage data for the event on 2020 January 20 enabled a sky localization of the source to within 14 arcmin(2) (90% confidence). The FRB localization is close to M81, a spiral galaxy at a distance of 3.6 Mpc. The FRB appears on the outskirts of M81 (projected offset similar to 20 kpc) but well inside its extended H i and thick disks. We empirically estimate the probability of a chance coincidence with M81 to be <10(-2). However, we cannot reject a Milky Way halo origin for the FRB. Within the FRB localization region, we find several interesting cataloged M81 sources and a radio point source detected in the Very Large Array Sky Survey. We search for prompt X-ray counterparts in Swift Burst Alert Telescope and Fermi/GBM data, and, for two of the FRB 20200120E bursts, we rule out coincident SGR 1806-20-like X-ray bursts. Due to the proximity of FRB 20200120E, future follow-up for prompt multiwavelength counterparts and subarcsecond localization could be constraining of proposed FRB models.

Automated summary

We report the discovery of FRB 20200120E, a repeating fast radio burst with a low dispersion measure, detected by the Canadian Hydrogen Intensity Mapping Experiment FRB project. The FRB is located near the spiral galaxy M81 at a distance of 3.6 Mpc. Several cataloged M81 sources and a radio point source have been found within the localization region of the FRB.