Search for giant planets in M 67 V: A warm Jupiter orbiting the turn-off star S1429

Context. 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 M 67' of 88 stars in the open cluster M 67, which led to the discovery of five giant planets, including three close-in (P < 10 days) hot-Jupiters.
Aims: In this work, we continue and extend the observation of stars in M 67, with the aim being to search for additional planets.
Methods: We conducted spectroscopic observations with the Habitable Planet Finder (HPF), HARPS, HARPS-North, and SOPHIE spectrographs of 11 stars in M 67. 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.
Results: 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_-0.19^+0.18] days and a minimum mass of M sin i = 1.80 ± 0.2 M_J. We update the hot-Jupiter occurrence rate in M 67 to include the five new stars, deriving [4.2_-2.3^+4.1 %] when considering all stars, and [5.4_-3.0^+5.1 %] if binary star systems are removed.