Dynamical origin of the secondary HD 118006 radial-velocity signal

Determine whether the approximately 11.8–21-day secondary radial-velocity signal observed in HD 118006 is dynamically induced by an orbiting body rather than produced by stellar activity or correlated noise.

Background

HD 118006 has a robust 4.93-day radial-velocity signal attributed to its Saturn-mass planet. A lower-amplitude secondary signal appears near 11.8 days, with alternative posterior solutions near 19–23 days, overlapping the star’s inferred rotation-related periodicities.

The authors find that this secondary variability can be represented either by a second Keplerian or by correlated noise modeled with a Gaussian process. Its physical origin therefore remains unresolved, and distinguishing these possibilities is necessary before treating it as an additional planet.

References

While the $P=4.93$\,d signal is persistent on the timescale of the observations, with $K = 22.5$\,-1, it is not clear that the second signal, with $K = 4.8$\,-1, is dynamically induced by an orbiting body.

— Three new exoplanet systems from the Dispersed Matter Planet Project  (2608.11902 - Barnes et al., 12 Aug 2026) in Section 4.2.2, subsection “recursive RV solution”

Although the ratio of $R_\textrm{var} / A$ is lower than we see for , we we were unable to recover reliable periodicities using the} s+leaf {GP model.

— Three new exoplanet systems from the Dispersed Matter Planet Project  (2608.11902 - Barnes et al., 12 Aug 2026) in Section 4.2.3, subsection “activity indicators and TESS photometry”