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

Stevens, Daniel J. and Howard, Andrew W. and Calchi Novati, Sebastiano and Fulton, Benjamin J. (2017) KELT-12b: A P ~ 5 day, Highly Inflated Hot Jupiter Transiting a Mildly Evolved Hot Star. Astronomical Journal, 153 (4). Art. No. 178. ISSN 0004-6256.

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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 T_(eff) = 6279 ± 51 K, log g⋆ = 3.89 ± 0.05, [Fe/H] = 0.19^(+0.08)_(-0.09), M* = 1.59^(+0.07)_(-0.09)M⊙, and R* = 2.37 ± 0.17 R⊙. The planetary companion has M_P = 0.95 ± 0.14 M_J, R_P = 1.78^(+0.17)_(-0.16)R_J, log g_P = 2.87^(+0.09)_(-0.10), and density ρ_P = 0.21^(+0.07)_(-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 BJD_(TDB) of 2,457,083.660459 ± 0.000894 and period of P = 5.0316216 ± 0.000032 days. 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) x 10^9 erg s^(−1) cm^(−2) from its host. We compare the radii and insolations of transiting gas giant planets around hot (T_(eff) ⩾ 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Howard, Andrew W.0000-0001-8638-0320
Calchi Novati, Sebastiano0000-0002-7669-1069
Fulton, Benjamin J.0000-0003-3504-5316
Additional Information:© 2017 The American Astronomical Society. Received 2016 August 16; revised 2017 January 28; accepted 2017 February 8; published 2017 March 24. The authors thank the anonymous reviewer and scientific editor for helpful suggestions regarding both form and content. Work by B.S.G. and D.J.S. was partially supported by NSF CAREER Grant AST-1056524. B.J.F. notes that this material is based on work supported by the National Science Foundation Graduate Research Fellowship under grant no. 2014184874. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors(s) and do not necessarily reflect the views of the National Science Foundation. K.K.M. acknowledges the purchase of SDSS filters for Whitin Observatory by the Theodore Dunham, Jr., Grant of the Fund for Astronomical Research. The NIRC2 AO data in this work were obtained at the W. M. Keck Observatory, which was financed by the W. M. Keck Foundation and is operated as a scientific partnership between the California Institute of Technology, the University of California, and NASA. K.P. acknowledges support from NASA grant NNX13AQ62G. DSSI data presented herein were obtained at the WIYN Observatory from telescope time allocated to NN-EXPLORE through the scientific partnership of the National Aeronautics and Space Administration, the National Science Foundation, and the National Optical Astronomy Observatory. This work was supported by a NASA WIYN PI Data Award, administered by the NASA Exoplanet Science Institute. We gratefully acknowledge the help of the DSSI team in observing KELT-12 and reducing the DSSI data. This work has made use of NASA's Astrophysics Data System, the Extrasolar Planet Encyclopedia at (Schneider et al. 2011), the SIMBAD database operated at CDS, Strasbourg, France, and the VizieR catalog access tool, CDS, Strasbourg, France (Ochsenbein et al. 2000). This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles; the Jet Propulsion Laboratory/California Institute of Technology, which is funded by the National Aeronautics and Space Administration; the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation; and the American Association of Variable Star Observers (AAVSO) Photometric All-Sky Survey (APASS), whose funding is provided by the Robert Martin Ayers Sciences Fund and the AAVSO Endowment (
Group:Infrared Processing and Analysis Center (IPAC), Astronomy Department
Funding AgencyGrant Number
NSF Graduate Research Fellowship2014184874
Fund for Astronomical ResearchUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:planets and satellites: individual (KELT-12b) – stars: individual (KELT-12, TYC 2619-1057-1)
Issue or Number:4
Record Number:CaltechAUTHORS:20170327-093110439
Persistent URL:
Official Citation:Daniel J. Stevens et al 2017 AJ 153 178
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75409
Deposited By: Tony Diaz
Deposited On:27 Mar 2017 16:59
Last Modified:06 Nov 2019 18:28

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