KELT-18b: Puffy Planet, Hot Host, Probably Perturbed

McLeod, Kim K. and Rodriguez, Joseph E. and Oelkers, Ryan J. and Collins, Karen A. and Bieryla, Allyson and Fulton, Benjamin J. and Stassun, Keivan G. and Gaudi, B. Scott and Penev, Kaloyan and Stevens, Daniel J. and Colon, Knicole D. and Pepper, Joshua and Narita, Norio and Ryu, Tsuguru and Fukui, Akihiko and Reed, Phillip A. and Tirrell, Bethany and Visgaitis, Tiffany and Kielkopf, John F. and Cohen, David H. and Jensen, Eric L. N. and Gregorio, Joao and Basturk, Ozgur and Oberst, Thomas E. and Melton, Casey and Kempton, Eliza M.-R. and Baldrige, Andrew and Zhao, Y. Sunny and Zambelli, Roberto and Latham, David W. and Esquerdo, Gilbert A. and Berlind, Perry and Calkins, Michael L. and Howard, Andrew W. and Isaacson, Howard and Weiss, Lauren M. and Benni, Paul and Beatty, Thomas G. and Eastman, Jason D. and Penny, Matthew T. and Siverd, Robert J. and Lund, Michael B. and Labadie-Bartz, Jonathan and Zhou, G. ORCID: and Curtis, Ivan A. and Joner, Michael D. and Manner, Mark and Relles, Howard and Scarpetta, Gaetano and Stephens, Denise C. and Stockdale, Chris and Tan, T. G. and DePoy, D. L. and Marshall, Jennifer L. and Pogge, Richard W. and Trueblood, Mark and Trueblood, Patricia (2017) KELT-18b: Puffy Planet, Hot Host, Probably Perturbed. The Astronomical Journal, 153 (6):263. pp. 1-15. ISSN 0004-6256

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We report the discovery of KELT-18b, a transiting hot Jupiter in a 2.87-day orbit around the bright (V = 10.1), hot, F4V star BD+60 1538 (TYC 3865-1173-1). We present follow-up photometry, spectroscopy, and adaptive optics imaging that allow a detailed characterization of the system. Our preferred model fits yield a host stellar temperature of K and a mass of, situating it as one of only a handful of known transiting planets with hosts that are as hot, massive, and bright. The planet has a mass of, a radius of, and a density of, making it one of the most inflated planets known around a hot star. We argue that KELT-18b's high temperature and low surface gravity, which yield an estimated ∼600 km atmospheric scale height, combined with its hot, bright host, make it an excellent candidate for observations aimed at atmospheric characterization. We also present evidence for a bound stellar companion at a projected separation of ∼1100 au, and speculate that it may have contributed to the strong misalignment we suspect between KELT-18's spin axis and its planet's orbital axis. The inferior conjunction time is 2457542.524998 ± 0.000416 (BJDTDB) and the orbital period is 2.8717510 ± 0.0000029 days. We encourage Rossiter-McLaughlin measurements in the near future to confirm the suspected spin-orbit misalignment of this system.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 03 Feb 2022 04:16
Last Modified: 07 Feb 2022 05:10
Uncontrolled Keywords: methods: observational; planets and satellites: detection; planets; and satellites: gaseous planets; stars: individual (BD+60 1538); techniques: photometric; techniques: radial velocities; Astrophysics - Earth and Planetary Astrophysics
Fields of Research (2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Socio-Economic Objectives (2020): 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences
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