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Constraining the Densities of the Three Kepler-289 Planets with Transit Timing Variations

Greklek-McKeon, Michael and Knutson, Heather A. and Vissapragada, Shreyas and Jontof-Hutter, Daniel and Chachan, Yayaati and Thorngren, Daniel and Vasisht, Gautam (2023) Constraining the Densities of the Three Kepler-289 Planets with Transit Timing Variations. Astronomical Journal, 165 (2). Art. No. 48. ISSN 0004-6256. doi:10.3847/1538-3881/ac8553.

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Kepler-289 is a three-planet system containing two sub-Neptunes and one cool giant planet orbiting a young, Sun-like star. All three planets exhibit transit timing variations (TTVs), with both adjacent planet pairs having orbital periods close to the 2:1 orbital resonance. We observe two transits of Kepler-289c with the Wide-field InfraRed Camera on the 200″ Hale Telescope at Palomar Observatory, using diffuser-assisted photometry to achieve space-like photometric precision from the ground. These new transit observations extend the original four-year Kepler TTV baseline by an additional 7.5 yr. We rereduce the archival Kepler data with an improved stellar activity correction and carry out a joint fit with the Palomar data to constrain the transit shapes and derive updated transit times. We then model the TTVs to determine the masses of the three planets and constrain their densities and bulk compositions. Our new analysis improves on previous mass and density constraints by a factor of two or more for all three planets, with the innermost planet showing the largest improvement. Our updated atmospheric mass fractions for the inner two planets indicate that they have hydrogen-rich envelopes, consistent with their location on the upper side of the radius valley. We also constrain the heavy element composition of the outer Saturn-mass planet, Kepler-289c, for the first time, finding that it contains 30.5 ± 6.9 M_⊕ of metals. We use dust evolution models to show that Kepler-289c must have formed beyond 1 au, and likely beyond 3 au, and then migrated inward.

Item Type:Article
Related URLs:
URLURL TypeDescription
Greklek-McKeon, Michael0000-0002-0371-1647
Knutson, Heather A.0000-0002-5375-4725
Vissapragada, Shreyas0000-0003-2527-1475
Jontof-Hutter, Daniel0000-0002-6227-7510
Chachan, Yayaati0000-0003-1728-8269
Thorngren, Daniel0000-0002-5113-8558
Vasisht, Gautam0000-0002-1871-6264
Additional Information:We thank the Palomar Observatory telescope operators, support astronomers, and directorate for their support of this work, especially Kajse Peffer, Kevin Rykoski, Carolyn Heffner, Andy Boden, and Tom Barlow. Part of this program is supported by JPL Hale telescope time allocation. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. H.A.K. acknowledges support from NSF CAREER grant 1555095. S.V. is supported by an NSF Graduate Research Fellowship. This research made use of Lightkurve, a Python package for Kepler and TESS data analysis (Lightkurve Collaboration et al. 2018). This research made use of exoplanet (Foreman-Mackey et al. 2021) and its dependencies (Astropy Collaboration et al. 2013; Kipping 2013; Salvatier et al. 2016; Theano Development Team 2016; Astropy Collaboration et al. 2018; Luger et al. 2019; Kumar et al. 2019; Agol et al. 2020).
Group:Division of Geological and Planetary Sciences
Funding AgencyGrant Number
NSF Graduate Research FellowshipUNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20230203-893210800.15
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:119012
Deposited By: Research Services Depository
Deposited On:07 Feb 2023 18:42
Last Modified:07 Feb 2023 18:42

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