A Distant Fast Radio Burst Associated with Its Host Galaxy by the Very Large Array

We present the discovery and subarcsecond localization of a new fast radio burst (FRB) by the Karl G. Jansky Very Large Array (VLA) and realfast search system. The FRB was discovered on 2019 June 14 with a dispersion measure of 959 $\mathrm{pc}\,{\mathrm{cm}}^{-3}$. This is the highest DM of any localized FRB and its measured burst fluence of 0.6 Jy ms is less than nearly all other FRBs. The source is not detected to repeat in 15 hr of VLA observing and 153 hr of CHIME/FRB observing. We describe a suite of statistical and data quality tests we used to verify the significance of the event and its localization precision. Follow-up optical/infrared photometry with Keck and Gemini associate the FRB with a pair of galaxies with $r\sim 23$ mag. The false-alarm rate for radio transients of this significance that are associated with a host galaxy is roughly $3\times {10}^{-4}\,{\mathrm{hr}}^{-1}$. The two putative host galaxies have similar photometric redshifts of ${z}_{\mathrm{phot}}\sim 0.6$, but different colors and stellar masses. Comparing the host distance to that implied by the dispersion measure suggests a modest ($\sim 50\,\mathrm{pc}\,{\mathrm{cm}}^{-3}$) electron column density associated with the FRB environment or host galaxy/galaxies.