CaltechAUTHORS
Published March 2021 | Version Accepted Version + Published
Journal Article Open

TESS–Keck Survey. IV. A Retrograde, Polar Orbit for the Ultra-low-density, Hot Super-Neptune WASP-107b

Creators

  • 1. ROR icon California Institute of Technology
  • 2. ROR icon University of Hawaii at Manoa
  • 3. ROR icon University of California, Berkeley
  • 4. ROR icon University of California, Irvine
  • 5. ROR icon University of Southern Queensland
  • 6. ROR icon University of California, Santa Cruz
  • 7. ROR icon University of Kansas
  • 8. ROR icon NASA Exoplanet Science Institute
  • 9. ROR icon University of California, Riverside
  • 10. ROR icon University of California, Los Angeles
  • 11. ROR icon Space Telescope Science Institute
  • 12. ROR icon Johns Hopkins University

Abstract

We measured the Rossiter–McLaughlin effect of WASP-107b during a single transit with Keck/HIRES. We found the sky-projected inclination of WASP-107b's orbit, relative to its host star's rotation axis, to be |λ| = 118⁺³⁸₋₁₉ degrees. This confirms the misaligned/polar orbit that was previously suggested from spot-crossing events and adds WASP-107b to the growing population of hot Neptunes in polar orbits around cool stars. WASP-107b is also the fourth such planet to have a known distant planetary companion. We examined several dynamical pathways by which this companion could have induced such an obliquity in WASP-107b. We find that nodal precession and disk dispersal-driven tilting can both explain the current orbital geometry while Kozai–Lidov cycles are suppressed by general relativity. While each hypothesis requires a mutual inclination between the two planets, nodal precession requires a much larger angle, which for WASP-107 is on the threshold of detectability with future Gaia astrometric data. As nodal precession has no stellar type dependence, but disk dispersal-driven tilting does, distinguishing between these two models is best done on the population level. Finding and characterizing more extrasolar systems like WASP-107 will additionally help distinguish whether the distribution of hot-Neptune obliquities is a dichotomy of aligned and polar orbits or if we are uniformly sampling obliquities during nodal precession cycles.

Additional Information

© 2021 The American Astronomical Society. Received 2020 November 10; revised 2020 December 1; accepted 2020 December 4; published 2021 February 15. We thank Konstantin Batygin, Cristobol Petrovich, and Jerry Xuan for helpful comments and productive discussions on orbital dynamics, and Josh Winn for constructive feedback that improved this manuscript. R.A.R. and A.C. acknowledge support from the National Science Foundation through the Graduate Research Fellowship Program (DGE 1745301, DGE 1842402). C.D.D. acknowledges the support of the Hellman Family Faculty Fund, the Alfred P. Sloan Foundation, the David & Lucile Packard Foundation, and the National Aeronautics and Space Administration via the TESS Guest Investigator Program (80NSSC18K1583). I.J.M.C. acknowledges support from the NSF through grant AST-1824644. D.H. acknowledges support from the Alfred P. Sloan Foundation, the National Aeronautics and Space Administration (80NSSC18K1585, 80NSSC19K0379), and the National Science Foundation (AST-1717000). E.A.P. acknowledges the support of the Alfred P. Sloan Foundation. L.M.W. is supported by the Beatrice Watson Parrent Fellowship and NASA ADAP Grant 80NSSC19K0597. We thank the time assignment committees of the University of California, the California Institute of Technology, NASA, and the University of Hawai'i for supporting the TESS–Keck Survey with observing time at the W. M. Keck Observatory. We gratefully acknowledge the efforts and dedication of the Keck Observatory staff for support of HIRES and remote observing. We recognize and acknowledge the cultural role and reverence that the summit of Maunakea has within the indigenous Hawaiian community. We are deeply grateful to have the opportunity to conduct observations from this mountain. Facility: Keck I (HIRES). - Software: emcee (Foreman-Mackey et al. 2013), corner.py (Foreman-Mackey 2016), REBOUND/REBOUND/x (Rein & Liu 2012; Tamayo et al. 2019), SciPy (Virtanen et al. 2020), NumPy (Harris et al. 2020), Matplotlib (Hunter 2007).

Attached Files

Published - Rubenzahl_2021_AJ_161_119.pdf

Accepted Version - 2101.09371.pdf

Files

2101.09371.pdf

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Additional details

Identifiers

Eprint ID
108091
Resolver ID
CaltechAUTHORS:20210217-111259280

Related works

Describes
https://arxiv.org/abs/2101.09371 (URL)

Funding

NSF Graduate Research Fellowship
DGE-1745301
NSF Graduate Research Fellowship
DGE-1842402
Hellman Family Faculty Fund
Alfred P. Sloan Foundation
David and Lucile Packard Foundation
NASA
80NSSC18K1583
NSF
AST-1824644
NASA
80NSSC18K1585
NASA
80NSSC19K0379
NSF
AST-1717000
Beatrice Watson Parrent Fellowship
NASA
80NSSC19K0597

Dates

Created
2021-02-18
Created from EPrint's datestamp field
Updated
2021-11-16
Created from EPrint's last_modified field

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Caltech groups
Astronomy Department