KELT-12b: A P ∼ 5 day, Highly Inflated Hot Jupiter Transiting a Mildly Evolved Hot Star

Daniel J. Stevens, Karen A. Collins, B. Scott Gaudi, Thomas G. Beatty, Robert J. Siverd, Allyson Bieryla, Benjamin J. Fulton, Justin R. Crepp, Erica J. Gonzales, Carl T. Coker, Kaloyan Penev, Keivan G. Stassun, Eric L.N. Jensen, Andrew W. Howard, David W. Latham, Joseph E. Rodriguez, Roberto Zambelli, Valerio Bozza, Phillip A. Reed, Joao GregorioLars A. Buchhave, Matthew T. Penny, Joshua Pepper, Perry Berlind, Sebastiano Calchi Novati, Michael L. Calkins, Giuseppe D'Ago, Jason D. Eastman, D. Bayliss, Knicole D. Colón, Ivan A. Curtis, D. L. DePoy, Gilbert A. Esquerdo, Andrew Gould, Michael D. Joner, John F. Kielkopf, Jonathan Labadie-Bartz, Michael B. Lund, Mark Manner, Jennifer L. Marshall, Kim K. McLeod, Thomas E. Oberst, Richard W. Pogge, Gaetano Scarpetta, Denise C. Stephens, Christopher Stockdale, T. G. Tan, Mark Trueblood, Patricia Trueblood

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


We announce the discovery of KELT-12b, a highly inflated Jupiter-mass planet transiting the mildly evolved, V = 10.64 host star TYC 2619-1057-1. We followed up the initial transit signal in the KELT-North survey data with precise ground-based photometry, high-resolution spectroscopy, precise radial velocity measurements, and high-resolution adaptive optics imaging. Our preferred best-fit model indicates that the host star has = 6279 ±51 K, = 3.89 ±0.05, [Fe/H] = 0.19+0.08 -0.09, = M∗ = 1.59+0.07 0.09M, and R ∗= 2.37 ±0.17 . The planetary companion has Mp= 0.95 ±0.14 MJ, RP = 1.78+0.17-0.16 RJ, log gP = 2.87+0.9 -0.09 and density pp 0.210.07 0.05= g cm-3, making it one of the most inflated giant planets known. Furthermore, for future follow-up, we report a high-precision time of inferior conjunction in BJDTDB of 2,457,083.660459 ±0.000894 and period of P = 5.0316216 ± 0.000032days. Despite the relatively large separation of ∼0.07 au implied by its ∼5.03-day orbital period, KELT-12b receives significant flux of 2.38+0.32 -0.29 × 109 erg s-1 cm-2 from its host. We compare the radii and insolations of transiting gas giant planets around hot (Teff 6250 K) and cool stars, noting that the observed paucity of known transiting giants around hot stars with low insolation is likely due to selection effects. We underscore the significance of long-term ground-based monitoring of hot stars and space-based targeting of hot stars with the Transiting Exoplanet Survey Satellite to search for inflated gas giants in longer-period orbits.

Original languageEnglish (US)
Article number178
JournalAstronomical Journal
Issue number4
StatePublished - Apr 2017
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved.


  • planets and satellites: individual (KELT-12b)
  • stars: individual (KELT-12, TYC 2619-1057-1)


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