New Signs Pointing Toward a Correlation Between Astrophysical Neutrinos and Radio Flares

We use data from the first two epochs of the Very Large Array Sky Survey (VLASS) and the IceCube Neutrino Observatory to search for evidence of a correlation between radio variability and the detection of astrophysical neutrinos. Our work probes the radio population down to \(S_{3\,\text{GHz}}\gtrsim\) a few mJy, more than an order of magnitude fainter than previous analyses that aim to cross correlate radio variability with neutrino detections. We find an excess number of associations between flaring radio sources and neutrinos that were detected between the first and second VLASS observations at \(>2\sigma\) confidence. This excess is consistent with radio flares contributing \(\sim13\,\%\) of the astrophysical neutrinos observed by IceCube. Notably, \(\sim90\,\%\) of the radio flares associated with neutrinos are not detected at either \(\gamma\)-ray or X-ray wavelengths, highlighting the importance of deep radio observations for identifying potential electromagnetic counterparts to astrophysical neutrinos. No excess in the number of associations between the wider radio-variable population and the IceCube neutrinos is seen when no time constraint is placed on the neutrino detection. We predict that data from future VLASS epochs will see an excess number of associations between radio flares and neutrinos at the \(>3\sigma\) level, and expected improvements to the positional constraints on the neutrinos may increase that confidence to \(>5\sigma\), should our results be representative.