It is commonly believed that giant planets are formed beyond the water-ice line in the protoplanetary disc, where there is a lot of solid material rich in ice condensation. Then, planets migrate towards their host stars to orbits observed today. Theoretical studies usually indicate on two main scenarios of migration: disc-driven migration and high-eccentricity migration. The former would yield mainly circular orbits (or orbits with moderate eccentricities) due to interactions with the disc. The latter predicts that giant planets can move very close to their stars because of tidal dissipation of highly eccentric initial orbits occurring at periastron. The initial high eccentricities are thought to be produced after disc dissipation and have a dynamical origin. Planet-planet scattering, Kozai-type perturbations induced by a distant stellar or planetary companion on a highly inclined orbit, secular dynamics in multi-planet systems or a combination of these processes may excite planetary eccentricities. Calculations show that tidal dissipation inside the planet circularizes and shrinks the planetary orbit, yielding circular orbits for dynamical advanced systems.

Using a homogenous analysis of RV data for 231 transiting planets by Bonomo et al. (2017), we have selected systems that belong to one of the following categories of planets on

1) wide and circular orbits, 2) tight and eccentric orbits, 3) wide and eccentric orbits.

Wide orbits are defined as orbits with a ratio of the semi-major axis and the planetary Roche limit greater than 5. The planets from the first category could migrate through disc-driven migration, and could be in fact members of compact multi-planetary systems, similar to WASP-47. Precise transit timing could bring detection of nearby low-mass planetary companions or put upper constraints on their masses. The orbits of planets from the second category are expected to be circularized in timescales of 1-10 million yr, so very quickly when compared to age of their systems (usually of the order of Gyr). We propose to focus on the systems that are dynamically advanced, so their orbits should have circularized long time ago. A non-zero eccentricity could be a hint for existence of additional planetary companions that dynamical induces the eccentricity. We also propose to acquire transit light curves for the systems from the third category. If the existence of a perturbing planet can be excluded in such systems, this negative result would be in favor of the high-eccentricity migration.

HAT-P-16 b: A possible sign of longterm variation has been detected:

PI: Gracjan Maciejewski gmac@umk.pl