Characterizing Transiting Extrasolar Planets
2016
The detection of the first planets outside our solar system two decades ago has spurred growing efforts to detect new planets. Thanks to improvements in spectroscopic and photometric technology fed by ten years experience, more and more planets have been found showing an astounding diversity of physical and orbital characteristics. At the same time, great efforts are spent on the characterization
of the known planets in order to understand their composition, especially as this can give insights into
planet formation processes.
The work presented in this thesis is pointed on one side towards the identification and confirmation of new exoplanets, on the other side towards the characterization of known transiting exoplanetary systems.
Regarding the first science case, two different works are reported: the discovery of two new planetary systems within the HATSouth (HATS-15 and HATS-16) collaboration and the confirmation of the planetary nature of the Kepler candidate Kepler-432 b.
HATS-15 b and HATS-16 b are two massive planets (with masses of ∼ 2.2 MJup and ∼ 3.3 MJup respectively) orbiting around two old G-type stars (age ∼ 10 Gyr). The short rotation period of HATS-16 b points towards a tidal interaction with the planet that resulted in a spun-up.
Kepler-432 is a sub-giant star ascending the red-giant branch. It hosts a massive planet (∼ 5 MJup) orbiting on a moderately eccentric orbit. Among other planets around evolved stars, Kepler-432 b is extremely rare being one of the few on a tight orbit (a < 0.5 au), challenging evolution and dynamical theories.
The main idea of the latter project is to perform follow-up observations of known transiting extrasolar planets in order to accurately characterize their systems. Further information, such as planetary atmosphere composition or stellar spin-orbit alignment, can be achieved by using different observing strategies: monitoring the same transit with two different facilities or perform simultaneous observations in different bands with instruments as BUSCA (CAHA) or GROND (La Silla). The characterization of six planetary systems and the successful exploit of the two observing strategies are presented.
Two planetary systems were observed simultaneously from two sites: HAT-P-16 and WASP-21. For HAT-P-23, WASP-45, WASP-46 and WASP-48 we obtained multi-band observations. For all the systems studied, a preciser measurements for the physical parameters was obtained. Moreover, all the
planets are smaller than previously known. The planetary densities are therefore higher and in some
cases the variation is significant (e.g. WASP-45 b), leading to a planet’s size compatible with a model
predicting a core 50 M⊕ .
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