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Squad up: WASP-107b joins an emerging population of hot polar Neptunes around cool stars

Presentation #102.358 in the session Poster Session.

Published onJun 20, 2022
Squad up: WASP-107b joins an emerging population of hot polar Neptunes around cool stars

How are these low mass planets around cool stars winding up on polar orbits? We observed the Rossiter-McLaughlin effect during a single transit of WASP-107b with Keck/HIRES and found it circles its K-dwarf star on a polar, slightly retrograde orbit. This makes WASP-107b the fourth close-in polar Neptune around a cool star which is also seen to be actively losing its atmosphere (alongside HAT-P-11b, GJ 436b, and GJ 3470b), and the second which has a confirmed outer planetary companion (alongside HAT-P-11b). I will discuss the plausible hypotheses purportedly producing this new population of perpendicular planets. These include nodal precession, a disk-dispersal driven obliquity excitation, and planet-planet scattering events which lead to a high-eccentricity migration. Distinguishing between these mechanisms is best done on the population level, as each depends on stellar properties and system architectures in different ways. Other properties such eccentric orbits and mass-shedding atmospheres indicate a history of distant formation and inward migration, providing another clue. We should find and characterize more extrasolar systems like WASP-107 to examine if the distribution of hot-Neptune obliquities is indeed a dichotomy of aligned vs. polar orbits sculpted by formative dynamics, or if we instead happen to be randomly sampling obliquities during precession cycles.

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