A flat spectrum candidate for a track-type high energy neutrino emission event, the case of blazar PKS 0723-008

TL;DR

This paper identifies the flat-spectrum blazar PKS 0723-008 as a promising candidate for a high-energy neutrino source, linking its radio properties and potential black hole evolution to neutrino emission.

Contribution

It proposes a novel scenario connecting binary black hole evolution and jet activity to high-energy neutrino production in blazars.

Findings

PKS 0723-008's coordinates match neutrino event ID5.

The blazar exhibits a flat spectrum up to high frequencies.

Radio flux increased fivefold over the last decade.

Abstract

By cross-correlating both the Parkes Catalogue and the Second Planck Catalogue of Compact Sources with the arrival direction of the track-type neutrinos detected by the IceCube Neutrino Observatory, we find the flat-spectrum blazar PKS 0723-008 as a good candidate for the high-energy neutrino event 5 (ID5). Apart from its coordinates matching those of ID5, PKS 0723-008 exhibits further interesting radio properties. Its spectrum is flat up to high Planck frequencies, and it produced a fivefold-increased radio flux density through the last decade. Based upon these radio properties we propose a scenario of binary black hole evolution leading to the observed high-energy neutrino emission. The main contributing events are the spin-flip of the dominant black hole, the formation of a new jet with significant particle acceleration and interaction with the surrounding material, with the corresponding increased radio flux. Doppler boosting from the underlying jet pointing to the Earth makes it possible to identify the origin of the neutrinos, so the merger itself is the form of an extended flat-spectrum radio emission, a key selection criterion to find traces of this complex process.