Long-term coherence of active stellar longitudes in HD 67200

Determine whether active regions or active longitudes on HD 67200 maintain a stable phase relationship over the 6.25-year observational baseline, thereby establishing whether the 15.99-day chromospheric periodicity can reliably represent stellar rotation.

Background

HD 67200 exhibits a tentative 15.99-day periodicity in the Mount Wilson S-index, broadly consistent with the expected stellar rotation period. The authors note that confirming this interpretation would require chromospheric structures to remain at relatively fixed longitudes over the full 6.25-year span of the observations.

Because stellar active regions evolve and activity levels vary between observing epochs, the persistence of a stable phase relationship is unresolved. This affects the interpretation of radial-velocity variability as either stellar activity or planetary motion.

References

Confirmation of a $15.99$\,d stellar rotation period for would imply active regions contributing significant chromospheric variability are present at relatively fixed longitudes on the $6.25$\,year span of the observations. Even if active longitudes exist, as has been suggested for over 100 years of solar data by , the long-term coherence of such structures remains unclear.

— Three new exoplanet systems from the Dispersed Matter Planet Project  (2608.11902 - Barnes et al., 12 Aug 2026) in Section 4.1.4, subsection “Activity indicators”