The Rossiter–McLaughlin effect revolutions: an ultra-short period planet and a warm mini-Neptune on perpendicular orbits

Bourrier, V.; Lovis, C.; Cretignier, M.; Allart, R.; Dumusque, X.; Delisle, J.-B.; Deline, A.; Sousa, S. G.; Adibekyan, V.; Alibert, Y.; Barros, S. C. C.; Borsa, F.; Cristiani, S.; Demangeon, O.; Ehrenreich, D.; Figueira, P.; González Hernández, J. I.; Lendl, M.; Lillo-Box, J.; Lo Curto, G.; ... (2021). The Rossiter–McLaughlin effect revolutions: an ultra-short period planet and a warm mini-Neptune on perpendicular orbits. Astronomy and astrophysics, 654, A152. EDP Sciences 10.1051/0004-6361/202141527

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Comparisons of the alignment of exoplanets with a common host star can be used to distinguish among concurrent evolution scenarios. However, multi-planet systems usually host mini-Neptunes and super-Earths, whose size make orbital architecture measurements challenging. We introduce the Rossiter-McLaughlin effect Revolutions technique, which can access spin-orbit angles of small planets by exploiting the full information contained in spectral transit time series. We validated the technique on published HARPS-N data of the mini-Neptune HD3167c, refining its high sky-projected spin-orbit angle (-108.9+5.4-5.5 deg), and we applied it to new ESPRESSO observations of the super-Earth HD3167b, revealing an aligned orbit (-6.6+6.6-7.9 deg). Surprisingly different variations in the contrast of the stellar lines occulted by the planets can be reconciled with a latitudinal dependence of the stellar line shape. In this scenario, a joint fit to both datasets constrains the inclination of the star (111.6+3.1-3.3 deg) and the 3D spin-orbit angles of HD3167b (29.5+7.2-9.4 deg) and HD3167c (107.7+5.1-4.9 deg). The projected spin-orbit angles do not depend on the model for the line contrast variations, and so, with a mutual inclination of 102.3+7.4-8.0 deg, we conclude that the two planets are on perpendicular orbits. This could be explained by HD3167b being strongly coupled to the star and retaining its primordial alignment, whereas HD3167c would have been brought to a nearly polar orbit via secular gravitational interactions with an outer companion. Follow-up observations and dynamical evolution simulations are required to search for this companion and explore this scenario. HD3167b is the smallest exoplanet with a confirmed spectroscopic Rossiter-McLaughlin signal. Our new technique opens the way to determining the orbital architectures of the super-Earth and Earth-sized planet populations.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences > Theoretical Astrophysics and Planetary Science (TAPS)
08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute
08 Faculty of Science > Physics Institute > NCCR PlanetS

UniBE Contributor:

Alibert, Yann Daniel Pierre

Subjects:

500 Science
500 Science > 520 Astronomy
500 Science > 530 Physics
600 Technology > 620 Engineering

ISSN:

0004-6361

Publisher:

EDP Sciences

Language:

English

Submitter:

Janine Jungo

Date Deposited:

28 Mar 2022 14:33

Last Modified:

05 Dec 2022 16:12

Publisher DOI:

10.1051/0004-6361/202141527

BORIS DOI:

10.48350/166491

URI:

https://boris.unibe.ch/id/eprint/166491

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