First results from the Warm Object Rossiter-McLaughlin Survey (WORMS)

Kurzfassung

First results from the Warm Object Rossiter-McLaughlin Survey (WORMS) The origins of warm Jupiters (WJs) are unclear. If they formed beyond the snow line, far from their host stars, then migration is required to bring them to their current orbits, but we don’t know which migration mechanism(s) are the most important. Obliquity (the angle between the stellar rotation and planetary orbital axes) is a key tracer of migration history. Dynamically violent, high eccentricity migration leads to planets in significantly misaligned orbits with large obliquities, whereas disc-driven migration should result in orbits coplanar with the stellar equator. In contrast to the hot Jupiters, the imprint of dynamical migration in WJs should not be erased through tidal interactions with the convective zone of their stars, because they are tidally detached. We have a two-year VLT/ESPRESSO programme to measure the obliquities of an unbiased sample of eleven WJs, which alongside other recent results, will greatly increase the size of the measured sample. Our first observations were made last year, and here we present the data gathered so far, and our preliminary interpretation. As already seen, there are hints of an unexpected correlation with orbital eccentricity, as well as tentative evidence for the orbits of lower-mass planets to be preferentially misaligned with respect to the stellar spin axis. An improved understanding of migration mechanisms operating at all orbital distances is vital for a complete picture of planetary formation and evolution.