The Astronomical Journal (Jan 2024)
KPF Confirms a Polar Orbit for KELT-18 b
- Ryan A. Rubenzahl,
- Fei Dai,
- Samuel Halverson,
- Andrew W. Howard,
- Aaron Householder,
- Benjamin Fulton,
- Aida Behmard,
- Steven R. Gibson,
- Arpita Roy,
- Abby P. Shaum,
- Howard Isaacson,
- Max Brodheim,
- William Deich,
- Grant M. Hill,
- Bradford Holden,
- Russ R. Laher,
- Kyle Lanclos,
- Joel N. Payne,
- Erik A. Petigura,
- Christian Schwab,
- Chris Smith,
- Guðmundur Stefánsson,
- Josh Walawender,
- Sharon X. Wang,
- Lauren M. Weiss,
- Joshua N. Winn,
- Edward Wishnow
Affiliations
- Ryan A. Rubenzahl
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA
- Fei Dai
- ORCiD
- Division of Geological and Planetary Sciences , 1200 E California Blvd, Pasadena, CA 91125, USA; Institute for Astronomy, University of Hawai’i , 2680 Woodlawn Dr, Honolulu, HI 96822, USA
- Samuel Halverson
- ORCiD
- Jet Propulsion Lab , Pasadena, CA 91125, USA
- Andrew W. Howard
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, 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
- Benjamin Fulton
- ORCiD
- NASA Exoplanet Science Institute/Caltech-IPAC , MC 314-6, 1200 E. California Blvd, Pasadena, CA 91125, USA
- Aida Behmard
- ORCiD
- American Museum of Natural History , 200 Central Park West, Manhattan, NY 10024, USA
- Steven R. Gibson
- ORCiD
- Caltech Optical Observatories , Pasadena, CA 91125, USA
- Arpita Roy
- ORCiD
- Astrophysics & Space Institute , Schmidt Sciences, New York, NY 10011, USA
- Abby P. Shaum
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA
- Howard Isaacson
- ORCiD
- 501 Campbell Hall, University of California at Berkeley , Berkeley, CA 94720, 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
- Bradford Holden
- ORCiD
- UC Observatories, University of California , Santa Cruz, CA 95064, USA
- Russ R. Laher
- ORCiD
- NASA Exoplanet Science Institute/Caltech-IPAC , MC 314-6, 1200 E. California Blvd, Pasadena, CA 91125, USA
- Kyle Lanclos
- ORCiD
- W. M. Keck Observatory , Waimea, HI 96743, USA
- Joel N. Payne
- ORCiD
- W. M. Keck Observatory , Waimea, HI 96743, USA
- Erik A. Petigura
- ORCiD
- Department of Physics & Astronomy, University of California Los Angeles , Los Angeles, CA 90095, USA
- Christian Schwab
- ORCiD
- School of Mathematical and Physical Sciences, Macquarie University , Balaclava Rd, North Ryde, NSW 2109, Australia
- Chris Smith
- Space Sciences Laboratory, University of California , Berkeley, CA 94720, USA
- Guðmundur Stefánsson
- ORCiD
- Anton Pannekoek Institute for Astronomy, University of Amsterdam , Science Park 904, 1098 XH Amsterdam, The Netherlands
- Josh Walawender
- ORCiD
- W. M. Keck Observatory , Waimea, HI 96743, USA
- Sharon X. Wang
- ORCiD
- Department of Astronomy, Tsinghua University , Beijing 100084, People's Republic of China
- Lauren M. Weiss
- ORCiD
- Department of Physics and Astronomy, University of Notre Dame , Notre Dame, IN 46556, USA
- Joshua N. Winn
- ORCiD
- Department of Astrophysical Sciences, Princeton University , Princeton, NJ 08544, USA
- Edward Wishnow
- Space Sciences Laboratory, University of California , Berkeley, CA 94720, USA
- DOI
- https://doi.org/10.3847/1538-3881/ad70b5
- Journal volume & issue
-
Vol. 168,
no. 5
p. 188
Abstract
We present the first spectroscopic transit results from the newly commissioned Keck Planet Finder on the Keck-I telescope at W. M. Keck Observatory. We observed a transit of KELT-18 b, an inflated ultrahot Jupiter orbiting a hot star ( T _eff = 6670 K) with a binary stellar companion. By modeling the perturbation to the measured cross-correlation functions using the Reloaded Rossiter–McLaughlin technique, we derived a sky-projected obliquity of λ = − 94.°8 ± 0.°7 ( $\psi ={93.8}_{-1.8}^{+1.6}\circ $ for isotropic i _⋆ ). The data are consistent with an extreme stellar differential rotation ( α = 0.9), though a more likely explanation is moderate center-to-limb variations of the emergent stellar spectrum. We see additional evidence for the latter from line widths increasing toward the limb. Using loose constraints on the stellar rotation period from observed variability in the available TESS photometry, we were able to constrain the stellar inclination and thus the true 3D stellar obliquity to $\psi ={91.7}_{-1.8}^{+2.2}\circ $ . KELT-18 b could have obtained its polar orbit through high-eccentricity migration initiated by Kozai–Lidov oscillations induced by the binary stellar companion KELT-18 B, as the two likely have a large mutual inclination as evidenced by Gaia astrometry. KELT-18 b adds another data point to the growing population of close-in polar planets, particularly around hot stars.
Keywords