GB6 J2113+1121: A Multiwavelength Flaring gamma-Ray Blazar Temporally and Spatially Coincident with the Neutrino Event IceCube-191001A

A radio-emitting tidal disruption event (AT2019dsg) is proposed as a likely counterpart to the IceCube neutrino event IC 191001A. In this work, we have revisited the Fermi-LAT data in the direction of the neutrino and confirmed no signal at the site of AT2019dsg. Instead, at the edge of the 90% confidence level error region of this neutrino, there is a gamma-ray transient source associated with the blazar GB6 J2113+1121. In 2019 May, GB6 J2113+1121 was undergoing a gamma-ray flare that is unprecedented since the start of the Fermi-LAT operation, with a variability amplitude of about 20 fold. Similar violent flares of GB6 J2113+1121, unobserved before, have also been detected in the optical bands. Moreover, the blazar remained in a high-flux state in the infrared bands when IC 191001A arrived, though the blazar 's gamma-ray and optical activities have temporarily ceased. Motivated by this spatial and temporal coincidence, we suggest that GB6 J2113+1121 is a candidate to be the counterpart to IC 191001A. The jet properties of GB6 J2113+1121 are investigated, which are found to be comparable with that of neutrino-emitting blazars (candidates). A specific analysis of archival IceCube data in this direction and future observations would put further constraints on the origin of the neutrino.