Secular Acceleration as a Deterministic Long-Term Trend in Precision Exoplanet Radial-Velocity Time Series

Kurzfassung

Slow linear or even curved trends can sometimes be detected in long-baseline radial velocity curves. One such trend is due to a purely geometric effect: the proper motion of the target which causes a continuously variable line of sight to a moving star. The effect can be parametrized by Gaia proper motion and parallax data. This RV-drift is characterized via \[ \dot v_{\rm sec}=2.298\times10^{-5} \frac{\mu_{\alpha *}^{2}+\mu_{\delta}^{2}}{\varpi} \ {\rm m\,s^{-1}\,yr^{-1}}, \] where the proper motions and parallax are in milliarcsecond (mas) yr$^{-1}$ and mas, respectively. The accumulated trend can reach or exceed meter-per-second level over several years for nearby high-proper-motion targets. This contribution should be reported in precise RV analyses and is relevant for future multi-year ground-based RV follow-up of PLATO targets as well as it can be important for planetary systems hosting Earth- and SuperEarth-like planet in the habitable zones of Solar-like stars.