Search for Giant Planets in M67 V: a Warm Jupiter Orbiting the Turn-off Star S1429

Planets orbiting members of open or globular clusters offer a great opportunity to study exoplanet populations systematically, as stars within clusters provide a mostly homogeneous sample, at least in chemical composition and stellar age. However, even though there have been coordinated efforts to search for exoplanets in stellar clusters, only a small number of planets have been detected. One successful example is the seven-year radial velocity (RV) survey `Search for giant planets in M67' of 88 stars in the open cluster M67, which led to the discovery of five giant planets, including three close-in ($P < 10$ days) hot-Jupiters. In this work, we continue and extend the observation of stars in M67, with the aim being to search for additional planets. We conducted spectroscopic observations with the Habitable Planet Finder (HPF), HARPS, HARPS-North, and SOPHIE spectrographs of 11 stars in M67. Six of our targets showed a variation or long-term trends in their RV during the original survey, while the other five were not observed in the original sample, bringing the total number of stars to 93. An analysis of the RVs reveals one additional planet around the turn-off point star S1429 and provides solutions for the orbits of stellar companions around S2207 and YBP2018. S1429 b is a warm-Jupiter on a likely circular orbit with a period of $77.48_ $ days and a minimum mass of $ M i = 1.80 0.2$ M$_ J $. We update the hot-Jupiter occurrence rate in M67 to include the five new stars, deriving $4.2_ $ when considering all stars, and $5.4_ $ if binary star systems are removed.