No precise localization for FRB 150418: claimed radio transient is AGN variability

Understand

Keane et al.

• have recently claimed to have obtained the first precise localization for a Fast Radio Burst (FRB) thanks to the identification of a contemporaneous fading slow (~week-timescale) radio transient.
• They use this localization to pinpoint the FRB to a galaxy at z ~ 0.49 that exhibits no discernable star formation activity.
• We argue that the transient is not genuine and that the host candidate, WISE J071634.59-190039.2, is instead a radio variable: the available data did not exclude this possibility; a random radio variable consistent with the observations is not unlikely to have a redshift compatible with the FRB dispersion measure; and the proposed transient light curve is better explained as a scintillating steady source, perhaps also showing an active galactic nucleus (AGN) flare, than a synchrotron-emitting blastwave.