PKS 1424+240: yet another masquerading BL Lac object as a possible IceCube neutrino source

TL;DR

This paper identifies PKS 1424+240 as a masquerading BL Lac object similar to TXS 0506+056, suggesting such sources could be significant neutrino emitters due to their unique properties and jet compositions.

Contribution

It reveals that certain high-energy neutrino sources are masquerading BL Lac objects with specific spectral and jet characteristics, expanding the understanding of potential neutrino emitters.

Findings

PKS 1424+240 shares properties with TXS 0506+056, including spectral energy distribution and high powers.

Masquerading BL Lac objects may be key neutrino sources due to their jet composition and particle acceleration.

A rare subclass of blazars, including about 20 Fermi-4LAC sources, could be significant neutrino emitters.

Abstract

We show that the blazar PKS 1424+240, which has been recently associated by IceCube with a neutrino excess at the $3.3\,\sigma$ level together with three other sources, is similar to the first plausible non-stellar neutrino source, TXS 0506+056, in being also a masquerading BL Lac object, i.e., intrinsically a flat-spectrum radio quasar with hidden broad lines and a standard accretion disk. We point out that these two sources share other properties, including spectral energy distribution, high powers, parsec scale properties, and possibly radio morphology. We speculate that the relatively rare combination of proton-loaded jets, possibly typical of high-excitation sources, and efficient particle acceleration processes, related to their relatively high synchrotron peak frequencies, might favour neutrino production in these two sources. GB6 J1542+6129, which has also recently appeared twice in a list of IceCube associations, seems also to belong to this rare blazar sub-class, which includes at most ~ 20 Fermi-4LAC blazars.