A possible misaligned orbit for the young planet AU Mic c
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Published version
Author(s)
Type
Journal Article
Abstract
The AU Microscopii planetary system is only 24 Myr old, and its geometry may provide clues about the early dynamical history of planetary systems. Here, we present the first measurement of the Rossiter–McLaughlin effect for the warm sub Neptune AU Mic c, using two transits observed simultaneously with the European Southern Observatory’s (ESO’s) Very Large Telescope (VLT)/Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO), CHaracterising ExOPlanet Satellite (CHEOPS), and Next-Generation Transit Survey (NGTS). After correcting for flares and for the magnetic activity of the host star, and accounting for transit-timing variations, we find the sky-projected spin–orbit angle of planet c to be in the range λc = 67.8+31.7 −49.0 degrees (1σ). We examine the possibility that planet c is misaligned with respect to the orbit of the inner planet b (λb = −2.96+10.44 −10.30), and the equatorial plane of the host star, and discuss scenarios that could explain both this and the planet’s high density, including secular interactions with other bodies in the system or a giant impact. We note that a significantly misaligned orbit for planet c is in some degree of tension with the dynamical stability of the system, and with the fact that we see both planets in transit, though these arguments alone do not preclude such an orbit. Further observations would be highly desirable to constrain the spin–orbit angle of planet c more precisely.
Date Issued
2025-01-03
Online Publication Date
2025-01-08T14:33:25Z
Date Acceptance
2024-11-23
ISSN
0035-8711
Publisher
Oxford University Press (OUP)
Start Page
2046
End Page
2063
Journal / Book Title
Monthly Notices of the Royal Astronomical Society
Volume
536
Issue
3
Copyright Statement
© 2024 The Author(s).
Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium,
provided the original work is properly cited.
Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium,
provided the original work is properly cited.
License URI
Identifier
https://doi.org/10.1093/mnras/stae2655
Publication Status
Published
Date Publish Online
2024-11-27