Propagation time from the jet base to the radio-emitting region

Determine the propagation time from the compact X-ray-emitting corona or another upstream location to the radio-emitting region in the jet of NGC 1275, and characterize the physical factors governing that propagation time.

Background

The paper identifies a possible delay of approximately 300 days between the onset of the 2023 X-ray flare and enhanced 43 GHz radio emission. This delay could represent propagation from the X-ray corona near the black hole to a radio-emitting region, or propagation between two locations farther downstream in the jet.

Because the available X-ray and radio light curves are sparsely sampled, the relevant propagation time cannot currently be established. Measuring it would help test disk–jet coupling and determine whether the observed radio enhancement is physically connected to the X-ray flare.

References

The propagation time from the base of a jet to the radio-emitting regions is largely unknown and may depend on many factors; it is possible that the points above 4~Jy in the 43~GHz VLBA light curve signal a \sim300 day propagation time between a compact X-ray corona and radio-emitting region, or between two regions downstream in the jet.

— X-ray Flaring and Variability in NGC 1275, the Heart of the Perseus Cluster  (2608.13281 - Ketchum et al., 13 Aug 2026) in Section 4, Discussion