Linearity of activity-indicator and radial-velocity correlations for HD 67200

Determine whether the Mount Wilson S-index or the full width at half maximum activity indicator correlates linearly with the radial velocities of HD 67200, rather than with a time derivative or another non-linear activity diagnostic.

Background

The authors find weak or inconsistent correlations between HD 67200 radial velocities and several activity indicators, with the apparent relationship varying between observing epochs. They note that stellar-activity-induced radial velocities may correlate with derivatives of activity indicators rather than with the indicators themselves.

This uncertainty matters because a reliable activity correlation would help determine whether the short-period radial-velocity signals are planetary or stellar in origin.

References

Also, it is not clear that {S$_\textrm{MW}$ or FWHM} should correlate linearly with RV; showed that the RVs correlate with the time derivative of .

— 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”