TY - JOUR
T1 - Orbital alignment of HD 332231 b
T2 - The warm Saturn HD 332231 b/TOI-1456 b travels on a well-aligned, circular orbit around a bright F8 dwarf
AU - Knudstrup, E.
AU - Albrecht, S. H.
N1 - Publisher Copyright:
© 2022 Authors
PY - 2022/4
Y1 - 2022/4
N2 - Context. Contrary to the orthodox picture of planet formation resulting in a neatly ordered Solar System, exoplanet systems exhibit highly diverse orbits: short and long periods, circular and eccentric, well- and misaligned, and even retrograde orbits. In order to understand this diversity it is essential to probe key orbital parameters. Spin-orbit alignment is such a parameter and can provide information about the formation and migration history of the system. However, tidal circularisation and alignment might hamper interpretations of orbital eccentricity and obliquities in the context of planet formation and evolution for planets on orbits shorter than about 10 days. Aims. Here we aim to measure the projected stellar obliquity in the HD 332231system in which a warm (period ≈ 18.7 days) giant planet orbits a bright F star on a circular orbit. Methods. We observed the system during a transit with the HARPS-N spectrograph and obtained data on the Rossiter-McLaughlin effect. We analysed the spectroscopic transit data together with new TESS photometry employing three different analysis methods. Results. The results from the different approaches are fully consistent. We find a projected obliquity of -2 ± 6°, indicating the stellar spin axis to be well-aligned with the orbit of the planet. We furthermore find evidence for transit timing variations suggesting the presence of an additional third body in the system. Conclusions. Together with the low orbital eccentricity, the good alignment suggests that this warm giant planet has not undergone high-eccentricity migration.
AB - Context. Contrary to the orthodox picture of planet formation resulting in a neatly ordered Solar System, exoplanet systems exhibit highly diverse orbits: short and long periods, circular and eccentric, well- and misaligned, and even retrograde orbits. In order to understand this diversity it is essential to probe key orbital parameters. Spin-orbit alignment is such a parameter and can provide information about the formation and migration history of the system. However, tidal circularisation and alignment might hamper interpretations of orbital eccentricity and obliquities in the context of planet formation and evolution for planets on orbits shorter than about 10 days. Aims. Here we aim to measure the projected stellar obliquity in the HD 332231system in which a warm (period ≈ 18.7 days) giant planet orbits a bright F star on a circular orbit. Methods. We observed the system during a transit with the HARPS-N spectrograph and obtained data on the Rossiter-McLaughlin effect. We analysed the spectroscopic transit data together with new TESS photometry employing three different analysis methods. Results. The results from the different approaches are fully consistent. We find a projected obliquity of -2 ± 6°, indicating the stellar spin axis to be well-aligned with the orbit of the planet. We furthermore find evidence for transit timing variations suggesting the presence of an additional third body in the system. Conclusions. Together with the low orbital eccentricity, the good alignment suggests that this warm giant planet has not undergone high-eccentricity migration.
KW - Methods: observational
KW - Planet-star interactions
KW - Planets and satellites: dynamical evolution and stability
KW - Techniques: photometric
KW - Techniques: spectroscopic
UR - http://www.scopus.com/inward/record.url?scp=85128874840&partnerID=8YFLogxK
U2 - 10.1051/0004-6361/202142726
DO - 10.1051/0004-6361/202142726
M3 - Journal article
AN - SCOPUS:85128874840
SN - 0004-6361
VL - 660
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A99
ER -