Obliquities of exoplanet host stars

Measurements of the obliquities in exoplanet systems have revealed some remarkable architectures, some of which are very different from the Solar System. Nearly 200 obliquity measurements have been obtained through observations of the Rossiter–McLaughlin (RM) effect. Here, we report on observations of 19 planetary systems that led to 17 clear detections of the RM effect and 2 less secure detections. After adding the new measurements to the tally, we used the entire collection of RM measurements to investigate four issues that have arisen in the literature. i) Does the obliquity distribution show a peak at approximately 90°? We find tentative evidence that such a peak does exist when restricting attention to the sample of sub-Saturn planets and hot Jupiters orbiting F stars. ii) Are high obliquities associated with high eccentricities? We find the association to be weaker than previously reported, and that a stronger association exists between obliquity and orbital separation, possibly due to tidal obliquity damping at small separations. iii) How low are the lowest known obliquities? Among hot Jupiters around cool stars, we find the dispersion to be 1.4 ± 0.7°, smaller than the 6° obliquity of the Sun, which serves as additional evidence for tidal damping. iv) What are the obliquities of stars with compact and flat systems of multiple planets? We find that they generally have obliquities lower than 10°, with several remarkable exceptions possibly caused by wide-orbiting stellar or planetary companions.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2024-08-30
DOI
https://doi.org/10.1051/0004-6361/202450627
Citations
30
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
9.95

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article

Obliquities of exoplanet host stars

E. Knudstrup, L. A. Hirsch, E. Palle, F. Murgas et al.
30 citations
Astronomy and Astrophysics
Stellar, planetary, and galactic studies
9.95
article

Obliquities of exoplanet host stars

E. Knudstrup, L. A. Hirsch, E. Palle, F. Murgas, Y. Kawai, N. Narita, J. N. Winn, C. M. Persson, Nora L. Eisner, David A. Baker, Marcelo Aron Fetzner Keniger, H. Isaacson, D. Gandolfi, S. H. Albrecht, A. Chontos, Marcus L. Marcussen, M. Fridlund, A.W. Howard, Allyson Bieryla, J. J. Zanazzi
article en
30 citations

Abstract

Measurements of the obliquities in exoplanet systems have revealed some remarkable architectures, some of which are very different from the Solar System. Nearly 200 obliquity measurements have been obtained through observations of the Rossiter–McLaughlin (RM) effect. Here, we report on observations of 19 planetary systems that led to 17 clear detections of the RM effect and 2 less secure detections. After adding the new measurements to the tally, we used the entire collection of RM measurements to investigate four issues that have arisen in the literature. i) Does the obliquity distribution show a peak at approximately 90°? We find tentative evidence that such a peak does exist when restricting attention to the sample of sub-Saturn planets and hot Jupiters orbiting F stars. ii) Are high obliquities associated with high eccentricities? We find the association to be weaker than previously reported, and that a stronger association exists between obliquity and orbital separation, possibly due to tidal obliquity damping at small separations. iii) How low are the lowest known obliquities? Among hot Jupiters around cool stars, we find the dispersion to be 1.4 ± 0.7°, smaller than the 6° obliquity of the Sun, which serves as additional evidence for tidal damping. iv) What are the obliquities of stars with compact and flat systems of multiple planets? We find that they generally have obliquities lower than 10°, with several remarkable exceptions possibly caused by wide-orbiting stellar or planetary companions.

Astronomy and AstrophysicsVol. 690
Austin College (US), Leiden University (NL), California Institute of Technology (US), Planetary Science Institute (US), University of Hawaii System (US), Universidad de La Laguna (ES), University of Toronto (CA), Princeton University (US), Aarhus University (DK), University of Warwick (GB), Astrobiology Center (JP), Center for Astrophysics Harvard & Smithsonian (US), Instituto de Astrofísica de Canarias (ES), Tokyo Metropolitan Komaba High School (JP), Flatiron Health (United States) (US), Flatiron Institute (US), Leiden Observatory, University of Turin (IT), Chalmers University of Technology (SE), The University of Tokyo (JP), University of California, Berkeley (US)
National Aeronautics and Space Administration, W. M. Keck Foundation, California Institute of Technology, Aarhus Universitet, Space Telescope Science Institute, Stellar Astrophysics Centre, National Research Foundation, Danmarks Grundforskningsfond, Danmarks Frie Forskningsfond, Universitetet i Oslo, Háskóli Íslands, Turun Yliopisto, Stockholms Universitet, Instituto de Astrofísica de Canarias, Science Mission Directorate
Openalex Percentile: Top 1%
Stellar, planetary, and galactic studies
9.95
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