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Since its launch in 2013, the Gaia space telescope has provided precise measurements of the positions and magnitudes of over 1 billion stars. This has enabled extensive searches for stellar and sub-stellar companions through astrometric and…
SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems) is a five-year M-class mission proposed to ESA Cosmic Vision. Its purpose is to image and characterize long-period extrasolar planets and circumstellar disks…
The study of orbital resonances allows for the constraint of planetary properties of compact systems. We can predict a system's resonances by observing the orbital periods of the planets, as planets in or near mean motion resonance have…
Most planetary discoveries with the K2 and TESS missions are restricted to short periods because of the limited duration of observation. However, the re-observation of sky area allows for the detection of longer period planets. We describe…
Planets that orbit only one of the stars in stellar binary systems (i.e., circumstellar) are dynamically constrained to a limited range of orbital parameters and thus understanding conditions on their stability is of great importance in…
Classical Cepheid stars have been considered since more than a century as reliable tools to estimate distances in the universe thanks to their Period-Luminosity (P-L) relationship. Moreover, they are also powerful astrophysical…
I present a review of astrometric techniques and instrumentation utilized to search for, detect, and characterize extra-solar planets. First, I briefly summarize the properties of the present-day sample of extrasolar planets, in connection…
Observed properties of stars and planets in binary/multiple star systems provide clues to planet formation and evolution. We extended our survey for visual stellar companions to the hosts of transiting exoplanets by 21 stars, using the…
Population studies of Kepler's multi-planet systems have revealed a surprising degree of structure in their underlying architectures. Information from a detected transiting planet can be combined with a population model to make predictions…
We report the discovery of 14 low-mass binary systems containing mid-M to mid-L dwarf companions with separations larger than 250 AU. We also report the independent discovery of 9 other systems with similar characteristics that were…
A transiting planet invites us to measure its size, mass, orbital parameters, atmospheric composition, and other characteristics. But the invitation can only be accepted if the host star is bright enough for precise measurements of its flux…
The presence of a stellar companion closer than ~100 AU is likely to affect planet formation and evolution. Yet, the precise effects and their actual impact on planet occurrence are still debated. To bring observational constraints, we have…
[ABRIDGED] We present the results of a 3 year monitoring program of a sample of very low mass (VLM) field binaries using both astrometric and spectroscopic data obtained in conjunction with the laser guide star adaptive optics system on the…
The extrasolar planetary system around HR 8799 is the first multiplanet system ever imaged. It is also, by a wide margin, the highest mass system with >27 Jupiters of planetary mass past 25 AU. This is a remarkable system with no analogue…
We report techniques and results of a Palomar 200-inch (5 m) adaptive optics imaging survey of sub-stellar companions to solar-type stars. The survey consists of Ks coronagraphic observations of 21 FGK dwarfs out to 20 pc (median distance…
Planet formation is often considered in the context of one circumstellar disk around one star. Yet stellar binary systems are ubiquitous, and thus a substantial fraction of all potential planets must form and evolve in more complex,…
Many Kepler multiplanet systems have planet pairs near low-order, mean-motion resonances. In addition, many Kepler multiplanet systems have planets with orbital periods less than a few days. With the exception of Kepler-42, however, there…
The star-forming regions in Chamaeleon are one of the nearest (distance ~165 pc) and youngest (age ~2 Myrs) conglomerates of recently formed stars and the ideal target for population studies of star formation. We investigate a total of 16…
The presence of a stellar companion can place constraints on occurrence and orbital evolution of satellites orbiting exoplanets, i.e., exomoons. In this work we revise earlier orbital stability limits for retrograde orbits in the case of a…
We initiated the Robo-AO Kepler Planetary Candidate Survey in 2012 to observe each Kepler exoplanet candidate host star with high-angular-resolution visible-light laser-adaptive-optics imaging. Our goal is to find nearby stars lying in…