The flaring radio-bright blazar PKS 0215+015 coincident with the high energy neutrino alert IceCube-220225A

ATel #15247; A. V. Plavin (ASC Lebedev, MIPT), Y. Y. Kovalev (ASC Lebedev, MIPT, MPIfR), S. V. Troitsky (INR), Yu. A. Kovalev (ASC Lebedev), A. V. Popkov (MIPT, ASC Lebedev), M. L. Lister (Purdue U.), J. L. Gomez (IAA-CSIC), T. Hovatta (FINCA), S. Kiehlmann (IoA FORTH, OVRO), I. Liodakis (FINCA), A. C.S. Readhead (OVRO, Caltech), A. K. Erkenov (SAO RAS), Y. V. Sotnikova (SAO RAS), G. V. Zhekanis (SAO RAS)
on 28 Feb 2022; 19:03 UT
Credential Certification: Alexander Plavin (alexander@plav.in)

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The recent BRONZE neutrino alert IceCube-220225, GCN #31650, with an energy of 154 TeV is suggested to be associated with the radio-bright blazar PKS 0215+015 following the predictions of Plavin et al. (2020) analysis. We note that this is one of the brightest blazars in the radio sky.

We report that PKS 0215+015 is showing a major radio flare at millimeter and centimeter wavelengths since the middle of 2021. Flux densities exceed 3 Jy, and these levels are the highest over more than 20 years of observations. Being a bright radio blazar, this object is also gamma-ray bright, with a major flare reported by the Fermi collaboration in ATel #15243.

The object is a member of MOJAVE VLBA, OVRO and RATAN-600 monitoring programs. We summarize below results of its recent observations by these radio programs, which will continue observations of the blazar.

MOJAVE 15 GHz VLBA program: PKS 0215+015 is a member of the flux-density limited 1.5 Jy MOJAVE Quarter-Century AGN sample and is monitored regularly with the VLBA at 15 GHz by the MOJAVE team, see available images. VLBA observations at 15 GHz on January 3, 2022, show a very compact parsec-scale structure with a core dominance of 0.9 and core size of 0.12 mas or 1 parsec.

OVRO 15 GHz program: The OVRO 40-m Telescope has been regularly monitoring the source since 2008 at 15 GHz. PKS 0215+015 has been in a flaring state since February 2021, reaching its highest flux density of 3.44 Jy on the 10th of October 2021 and remaining at a similar level until February 2022.This is the brightest state of the source during the 14 years it is monitored by OVRO. The OVRO 40m Telescope at the California Institute of Technology is used to regularly monitor a large number of AGN at 15 GHz. It is currently supported by private funding from the California Institute of Technology and the Max Planck Institute for Radio Astronomy.

RATAN-600 1-22 GHz program: RATAN-600 instantaneous spectra of PKS 0215+015 at 1.2, 2.3, 4.7, 8.2, 11.2 and 22 GHz have been monitored since 1996. They show a typical behavior for blazar spectra: variable, mostly inverted or flattened near 22 GHz. The 22 GHz flux density was observed to reach 2.6+-0.1 Jy in November 2021 which is its highest state since 1999.

The radio flare was also reported in ATel #15245 on the basis of ATCA observations at 5-35 GHz in 2021. We encourage the community to monitor the blazar in the whole electromagnetic spectrum.