FRIENDS OF HOT JUPITERS. I. A RADIAL VELOCITY SEARCH FOR MASSIVE, LONG-PERIOD COMPANIONS TO CLOSE-IN GAS GIANT PLANETS

TLDR

We searched for distant massive companions to known transiting gas‑giant planets that may have influenced the dynamical evolution of these systems. We obtained new Keck HIRES radial‑velocity data for 51 transiting gas‑giant planets, identified significant accelerations in fifteen systems, and combined these measurements with Keck NIRC2 adaptive‑optics imaging and transit/eclipse constraints to constrain companion masses, orbital periods, and refine planetary parameters. We detected statistically significant accelerations in fifteen systems—six of which are newly reported—whose companion masses span 1–500 MJup and semi‑major axes 1–75 AU, with a 51 % ± 10 % occurrence rate for 1–13 MJup companions at 1–20 AU, and found no difference in companion frequency between systems with misaligned or eccentric inner planets and those with aligned, circular orbits.

Abstract

In this paper we search for distant massive companions to known transiting gas giant planets that may have influenced the dynamical evolution of these systems. We present new radial velocity observations for a sample of 51 planets obtained using the Keck HIRES instrument, and find statistically significant accelerations in fifteen systems. Six of these systems have no previously reported accelerations in the published literature: HAT-P-10, HAT-P-22, HAT-P-29, HAT-P-32, WASP-10, and XO-2. We combine our radial velocity fits with Keck NIRC2 adaptive optics (AO) imaging data to place constraints on the allowed masses and orbital periods of the companions responsible for the detected accelerations. The estimated masses of the companions range between 1–500 MJup, with orbital semi-major axes typically between 1–75 AU. A significant majority of the companions detected by our survey are constrained to have minimum masses comparable to or larger than those of the transiting planets in these systems, making them candidates for influencing the orbital evolution of the inner gas giant. We estimate a total occurrence rate of 51% ± 10% for companions with masses between 1–13 MJup and orbital semi-major axes between 1–20 AU in our sample. We find no statistically significant difference between the frequency of companions to transiting planets with misaligned or eccentric orbits and those with well-aligned, circular orbits. We combine our expanded sample of radial velocity measurements with constraints from transit and secondary eclipse observations to provide improved measurements of the physical and orbital characteristics of all of the planets included in our survey.