IceCube AGN Neutrino Source Candidate PKS 2233-148: Peculiar Observed Properties & Possible Gravitational Lensing Signatures

Abstract PKS 2233-148, the hottest spot in the southern hemisphere in IceCube neutrino detections, qualifies as one of the best objects to analyze the physical mechanisms involved. So far, only an upper limit for the redshift was known. We detect the neutral Fe Kα line (6.4 keV at rest frame) of the reflection component in the X-ray spectrum of Swift-XRT observations with 3.1σ significance and determine the so far unknown redshift to be z = 0.63 ± 0.04. We find a displacement of the jet and sudden offset emission from the jet ridge line in 15 GHz VLBA observations. The correlated multi-wavelength (radio - γ-rays) variability of PKS 2233-148 reveals strong and almost achromatic flaring which seems superimposed by at least one particularly fast ”flash” of flaring. A detailed analysis reveals the superposition of two flaring processes on very different timescales. The flare morphology, Bayesian model comparison, PSD behavior, and simplified lensing calculations indicate that several physically plausible scenarios remain viable. Assuming a microlensing origin, the mass derived for the ”fast” γ-ray flash is of the order of 10−8M⊙ and might result from gravitational lensing of a dark matter substructure. A similar ”fast” γ-ray flash coincides with the sudden offset jet emission seen in the VLBA observations. Delensing reconstruction maps the observed jet components into a more ordered and substantially straighter source-plane structure with a modest reduction in the reconstructed flux-density variability. PKS 2233-148 is the third IceCube neutrino emitting blazar counterpart, with gravitational lensing signatures and the first counterpart, with potential signatures for Dark matter substructure lensing.

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