Henry Ngo

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

In this paper we search for distant massive companions to known transiting hot Jupiters that may have influenced the dynamical evolution of these systems. We present new radial velocity observations for a sample of 51 hot Jupiters obtained using the Keck HIRES instrument, and use these observations to search for long-term radial velocity accelerations. We find new, statistically significant accelerations in seven systems, including: HAT-P-10, HAT-P-20, HAT-P-22, HAT-P-29, HAT-P-32, WASP-10, and XO-2. We combine our radial velocity fits with Keck NIRC2 AO imaging data to place constraints on the allowed masses and orbital periods of the companions. The estimated masses of the companions range between 1-500 M_(Jup), 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 short-period hot Jupiters in these systems, making them candidates for influencing the orbital evolution of the inner hot Jupiters. They also appear to occur preferentially in systems with more metal-rich host stars, and with typical orbital separations that are larger than those of multi-planet systems without hot Jupiters. We estimate a total occurrence rate of 55% +11% / -10% for companions with masses between 1-13 M_(Jup) and orbital semi-major axes between 1-20 AU in our sample. We find no statistically significant difference between the frequency of companions in hot Jupiter systems 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 hot Jupiters included in our survey.

Statistics of Long Period Gas Giant Planets in Known Planetary Systems

We conducted a Doppler survey at Keck combined with NIRC2 K-band AO imaging to search for massive, long-period companions to 123 known exoplanet systems with one or two planets detected using the radial velocity (RV) method. Our survey is sensitive to Jupiter mass planets out to 20 AU for a majority of stars in our sample, and we report the discovery of eight new long-period planets, in addition to 20 systems with statistically significant RV trends indicating the presence of an outer companion beyond 5 AU. We combine our RV observations with AO imaging to determine the range of allowed masses and orbital separations for these companions, and account for variations in our sensitivity to companions among stars in our sample. We estimate the total occurrence rate of companions in our sample to be 52 +/- 5% over the range 1 - 20 M_Jup and 5 - 20 AU. Our data also suggest a declining frequency for gas giant planets in these systems beyond 3-10 AU, in contrast to earlier studies that found a rising frequency for giant planets in the range 0.01-3 AU. This suggests either that the frequency of gas giant planets peaks between 3-10 AU, or that outer companions in these systems have a different semi-major axis distribution than the overall gas giant planet population. Our results also suggest that hot gas giants may be more likely to have an outer companion than cold gas giants. We find that planets with an outer companion have higher average eccentricities than their single counterparts, suggesting that dynamical interactions between planets may play an important role in these systems.

WASP-12b AND HAT-P-8b ARE MEMBERS OF TRIPLE STAR SYSTEMS

We present high spatial resolution images that demonstrate that WASP-12b and HAT-P-8b orbit the primary stars of hierarchical triple star systems. In each case, two distant companions with colors and brightnesses consistent with M dwarfs co-orbit the hot Jupiter planet host as well as one another. Our adaptive optics images spatially resolve the secondary around WASP-12, previously identified by Bergfors et al. and Crossfield et al. into two distinct sources separated by 84.3 ± 0.6 mas (21 ± 3 AU). We find that the secondary to HAT-P-8, also identified by Bergfors et al., is in fact composed of two stars separated by 65.3 ± 0.5 mas (15 ± 1 AU). Our follow-up observations demonstrate physical association through common proper motion. HAT-P-8 C has a particularly low mass, which we estimate to be 0.18 ± 0.02 M☉ using photometry. Due to their hierarchy, WASP-12 BC and HAT-P-8 BC will enable the first dynamical mass determination for hot Jupiter stellar companions. These previously well studied planet hosts now represent higher-order multi-star systems with potentially complex dynamics, underscoring the importance of diffraction-limited imaging and providing additional context for understanding the migrant population of transiting hot Jupiters.

Friends of Hot Jupiters. IV. Stellar companions beyond 50 AU might facilitate giant planet formation, but most are unlikely to cause Kozai-Lidov migration

Stellar companions can influence the formation and evolution of planetary systems, but there are currently few observational constraints on the properties of planet-hosting binary star systems. We search for stellar companions around 77 transiting hot Jupiter systems to explore the statistical properties of this population of companions as compared to field stars of similar spectral type. After correcting for survey incompleteness, we find that

Friends of hot Jupiters. III. An infrared spectroscopic search for low-mass stellar companions

47\%\pm7\%

EPIC 220204960: A Quadruple Star System Containing Two Strongly Interacting Eclipsing Binaries

of hot Jupiter systems have stellar companions with semi-major axes between 50-2000 AU. This is 2.9 times larger than the field star companion fraction in this separation range, with a significance of

On-sky performance of the QACITS pointing control technique with the Keck/NIRC2 vortex coronagraph

4.4\sigma

Near-infrared Emission Spectrum of WASP-103b Using Hubble Space Telescope/Wide Field Camera 3

. In the 1-50AU range, only

EPIC 201702477b: A Transiting Brown Dwarf from K2 in a 41 day Orbit

3.9^{+4.5}_{-2.0}\%

The QACITS pointing sensor: from theory to on-sky operation on Keck/NIRC2

of hot Jupiters host stellar companions compared to the field star value of