What's the (RV) Point? A $3.5\times$ Enhancement in Super-Jupiters with Saturn-like Periods from a Critical Observation

Abstract

Amidst the exoplanet revolution in which multiple techniques have successfully found planets, the Doppler (Radial Velocity, or "RV") technique is unique in its sensitivity to giant planets at long orbital periods around Sun-like stars. The upcoming retirement of Keck-HIRES will incur irreversible changes in the continuation of HIRES's decades-long stable RV baseline and with it, the exoplanet community's ability to detect giant exoplanets with periods longer than Jupiter. With the time elapsed from the last HIRES RV for many stars of interest at ~3 years and growing, we tested the impact of a "critical RV", one that would bridge this gap between past HIRES RVs and future stable Keck-KPF RVs, on the recovery of long-period giant exoplanets. We generated 2000 1-planet systems with RVs sampled at a representative timeseries and used the planet-finding code Octofitter to perform injection-recovery experiments including and omitting this critical RV for each system. For the injected long-period super-Jupiters (~8-55 years, 1-13 $M_J$), including the critical RV induced a $1.5\times$ enhancement in overall planet recovery and a more specific $3.5\times$ enhancement in the recovery of super-Jupiters with Saturn-like periods. These experiments show that gathering a critical RV for stars of interest can help ensure that HIRES's decades-long stable RV baseline in conjunction with future KPF RVs, or indeed that the observationally-gapped RV baselines of any instruments that will undergo an RV zeropoint offset, will continue to be foundational to the discovery of long-period giant exoplanets in years to come.