Determine whether the double-peaked activity is recurrent over the long term

Determine whether the similarity between the two observed active epochs of PKS 1424–418, including their recurrent double-peaked gamma-ray sub-flare morphology and characteristic time-scales, represents a recurrent long-term behaviour by obtaining and analysing further active epochs.

Background

The paper identifies candidate recurrent double-peaked gamma-ray sub-flares in PKS 1424–418 during two active epochs separated by approximately 3650 days. Both epochs exhibit similar intra-subflare peak separations of approximately 11.8 days and neighbouring-subflare spacings of approximately 67 days, and their overall sub-flare morphologies are reported to be strikingly similar.

The statistical tests indicate that the joint morphology is not easily reproduced by the adopted red-noise null model, but only two major active epochs are available. Consequently, the observations do not establish whether the apparent similarity reflects a stable, recurrent long-term property of the source or a chance resemblance between two active periods. Additional active epochs are therefore required to resolve this question.

References

This consistency raises the question of whether the 2015 and 2025 flares represent recurrent episodes of energy dissipation in the jet, in which similar physical conditions and jet power budgets can account for both high-activity episodes.

— Exceptional Gamma-Ray Flaring Activity of the Blazar S4 0954+65 in Early 2025  (2609.29873 - Ouyang et al., 24 Sep 2026) in Discussion, paragraph comparing the 2015 and 2025 flares

Further active epochs are required to determine whether this similarity represents a recurrent long-term behaviour.

— Recurrent double-peaked $γ$-ray sub-flares in PKS 1424-418  (2609.28932 - Wang et al., 24 Sep 2026) in Abstract; reiterated in Section 5, “Variability comparison,” and Section 6, “Conclusions”