One of the closest exoplanet pairs to the 3:2 Mean Motion Resonance: K2-19b \& c

The K2 mission has recently begun to discover new and diverse planetary systems. In December 2014 Campaign 1 data from the mission was released, providing high-precision photometry for ~22000 objects over an 80 day timespan. We searched these data with the aim of detecting further important new objects. Our search through two separate pipelines led to the independent discovery of K2-19b \& c, a two-planet system of Neptune sized objects (4.2 and 7.2 $R_\oplus$), orbiting a K dwarf extremely close to the 3:2 mean motion resonance. The two planets each show transits, sometimes simultaneously due to their proximity to resonance and alignment of conjunctions. We obtain further ground based photometry of the larger planet with the NITES telescope, demonstrating the presence of large transit timing variations (TTVs), and use the observed TTVs to place mass constraints on the transiting objects under the hypothesis that the objects are near but not in resonance. We then statistically validate the planets through the \texttt{PASTIS} tool, independently of the TTV analysis.Comment: 18 pages, 10 figures, accepted to A&A, updated to match published versio

Radial velocity detection and statistical analysis of substellar companions in the outer regions of extrasolar systems

This work studies massive long-period exoplanets, similar to Jupiter, orbiting nearby Sun-like stars in our galaxy. The main method used is Doppler spectroscopy, also known as the Radial Velocity method. This research is based on two observational programs: A follow-up of long-period exoplanet candidates observed by the ELODIE and SOPHIE spectrographs for over 20 years, and a follow-up of planetary systems containing a hot Jupiter and signals of an additional giant planet in a wider orbit, observed with the CORALIE spectrograph. The characteristics of each program are discussed, as well as the results found. Additionally, the possibility of these radial velocity signals being caused by stellar magnetic cycles is also discussed. When this is ruled out, the orbital parameters and characteristics of every system are estimated. Finally, this thesis explores the possible synergies between Radial Velocities and other exoplanet detection techniques such as Direct Imaging, Astro