Radial velocities of 2 hot Jupiters in Praesepe

These are the first known hot Jupiters in an open cluster and the only planets known to orbit Sun-like, main-sequence stars in a cluster. The planets are detected from Doppler-shifted radial velocities; line bisector spans and activity indices show no correlation with orbital phase, confirming the variations are caused by planetary companions.

Pr0201b orbits a V=10.52 late F dwarf with a period of 4.4264+/-0.0070 days and has a minimum mass of 0.540+/-0.039M_Jup_, and Pr0211b orbits a V=12.06 late G dwarf with a period of 2.1451+/-0.0012 days and has a minimum mass of 1.844+/-0.064M_Jup_. The detection of two planets among 53 single members surveyed establishes a lower limit of 3.8^+5.0^_-2.4_% on the hot Jupiter frequency in this metal-rich open cluster. Given the precisely known age of the cluster, this discovery also demonstrates that, in at least two cases, giant planet migration occurred within 600Myr after formation.