The Astronomical Journal (Jan 2024)
The HD 191939 Exoplanet System is Well Aligned and Flat
- Jack Lubin,
- Erik A. Petigura,
- Judah Van Zandt,
- Corey Beard,
- Fei Dai,
- Samuel Halverson,
- Rae Holcomb,
- Andrew W. Howard,
- Howard Isaacson,
- Jacob Luhn,
- Paul Robertson,
- Ryan A. Rubenzahl,
- Guđmundur Stefánsson,
- Joshua N. Winn,
- Max Brodheim,
- William Deich,
- Grant M. Hill,
- Steven R. Gibson,
- Bradford Holden,
- Aaron Householder,
- Russ R. Laher,
- Kyle Lanclos,
- Joel Payne,
- Arpita Roy,
- Roger Smith,
- Abby P. Shaum,
- Christian Schwab,
- Josh Walawender
Affiliations
- Jack Lubin
- ORCiD
- Department of Physics & Astronomy, University of California Los Angeles , Los Angeles, CA 90095, USA
- Erik A. Petigura
- ORCiD
- Department of Physics & Astronomy, University of California Los Angeles , Los Angeles, CA 90095, USA
- Judah Van Zandt
- ORCiD
- Department of Physics & Astronomy, University of California Los Angeles , Los Angeles, CA 90095, USA
- Corey Beard
- ORCiD
- Department of Physics & Astronomy, University of California Irvine , Irvine, CA 92697, USA
- Fei Dai
- ORCiD
- Institute for Astronomy, University of Hawai‘i , 2680 Woodlawn Drive, Honolulu, HI 96822, USA; Division of Geological and Planetary Sciences , 1200 E California Boulevard, Pasadena, CA 91125, USA; Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA
- Samuel Halverson
- ORCiD
- Jet Propulsion Laboratory, California Institute of Technology , 4800 Oak Grove Drive, Pasadena, CA 91109, USA
- Rae Holcomb
- ORCiD
- Department of Physics & Astronomy, University of California Irvine , Irvine, CA 92697, USA
- Andrew W. Howard
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA
- Howard Isaacson
- ORCiD
- Department of Astronomy, 501 Campbell Hall, University of California , Berkeley, CA 94720, USA; Centre for Astrophysics, University of Southern Queensland , Toowoomba, QLD, Australia
- Jacob Luhn
- ORCiD
- Department of Physics & Astronomy, University of California Irvine , Irvine, CA 92697, USA
- Paul Robertson
- ORCiD
- Department of Physics & Astronomy, University of California Irvine , Irvine, CA 92697, USA
- Ryan A. Rubenzahl
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA
- Guđmundur Stefánsson
- ORCiD
- Anton Pannekoek Institute for Astronomy, University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands
- Joshua N. Winn
- ORCiD
- Department of Astrophysical Sciences, Princeton University , Princeton, NJ 08544, USA
- Max Brodheim
- ORCiD
- W. M. Keck Observatory, Waimea, HI 96743, USA
- William Deich
- ORCiD
- UC Observatories, University of California , Santa Cruz, CA 95064, USA
- Grant M. Hill
- ORCiD
- W. M. Keck Observatory, Waimea, HI 96743, USA
- Steven R. Gibson
- ORCiD
- Caltech Optical Observatories, California Institute of Technology , Pasadena, CA 91125, USA
- Bradford Holden
- ORCiD
- UC Observatories, University of California , Santa Cruz, CA 95064, USA
- Aaron Householder
- ORCiD
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology , Cambridge, MA 02139, USA; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology , Cambridge, MA 02139, USA
- Russ R. Laher
- ORCiD
- NASA Exoplanet Science Institute/Caltech-IPAC , 1200 E California Boulevard, Pasadena, CA 91125, USA
- Kyle Lanclos
- ORCiD
- W. M. Keck Observatory, Waimea, HI 96743, USA
- Joel Payne
- ORCiD
- W. M. Keck Observatory, Waimea, HI 96743, USA
- Arpita Roy
- ORCiD
- Astrophysics & Space Institute , Schmidt Sciences, New York, NY 10011, USA
- Roger Smith
- ORCiD
- Caltech Optical Observatories, California Institute of Technology , Pasadena, CA 91125, USA
- Abby P. Shaum
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA
- Christian Schwab
- ORCiD
- School of Mathematical and Physical Sciences, Macquarie University , Balaclava Road, North Ryde, NSW 2109, Australia
- Josh Walawender
- ORCiD
- W. M. Keck Observatory, Waimea, HI 96743, USA
- DOI
- https://doi.org/10.3847/1538-3881/ad79ed
- Journal volume & issue
-
Vol. 168,
no. 5
p. 196
Abstract
We report the sky-projected spin–orbit angle λ for HD 191939 b, the innermost planet in a six-planet system, using Keck/KPF to detect the Rossiter–McLaughlin (RM) effect. Planet b is a sub-Neptune with radius 3.4 ± 0.8 R _⊕ and mass 10.0 ± 0.7 M _⊕ with an RM amplitude <1 m s ^−1 . We find the planet is consistent with a well-aligned orbit, measuring λ = 3.°7 ± 5.°0. Additionally, we place new constraints on the mass and period of the distant super-Jupiter, planet f, finding it to be 2.88 ± 0.26 M _J on a 2898 ± 152 days orbit. With these new orbital parameters, we perform a dynamical analysis of the system and constrain the mutual inclination of the nontransiting planet e to be smaller than 12° relative to the plane shared by the inner three transiting planets. Additionally, the further planet f is inclined off this shared plane, the greater the amplitude of precession for the entire inner system, making it increasingly unlikely to measure an aligned orbit for planet b. Through this analysis, we show that this system’s wide variety of planets are all well-aligned with the star and nearly coplanar, suggesting that the system formed dynamically cold and flat out of a well-aligned protoplanetary disk, similar to our own solar system.
Keywords
