Origin of the discrepant C2 production rates

Determine the origin of the discrepancy between the C2 production rates reported by different observational studies of interstellar comet 3I/ATLAS, including whether it arises from differences in observational data, analysis methodologies, production-rate assumptions, or aperture-dependent sampling of the extended coma.

Background

The paper compares C2 production rates derived from UVES observations with measurements from other facilities and finds that some post-perihelion values differ substantially. The authors note that the discrepancy may be related to observational or methodological differences, including the larger slit used in some observations and the hyperactive nature of 3I/ATLAS, which could cause different instruments to sample different fractions of an extended C2-emission region. However, the specific origin of the discrepancy remains unresolved.

References

The origin of this difference is not clear and may reflect differences in the observational data, analysis methodology, or other assumptions adopted in the production-rate derivation.

— High-resolution optical spectroscopy reveals the distinctive volatile composition of the interstellar comet 3I/ATLAS  (2609.26577 - Aravind et al., 22 Sep 2026) in Section 3.2, subsection “Heliocentric-distance scaling - Power law”