KELT-19Ab: A P ~ 4.6-day Hot Jupiter Transiting a Likely Am Star with a Distant Stellar Companion

Creators: Siverd, Robert; Zhou, George; Ciardi, David R.; Dressing, Courtney D.; Patel, Rahul

Abstract

We present the discovery of the giant planet KELT-19Ab, which transits the moderately bright (V ~ 9.9) A8V star TYC 764-1494-1 with an orbital period of 4.61 days. We confirm the planetary nature of the companion via a combination of radial velocities, which limit the mass to ≾ 4.1 M_J (3σ), and a clear Doppler tomography signal, which indicates a retrograde projected spin–orbit misalignment of λ = -179.7^(+3.7)_(-3.8) degrees. Global modeling indicates that the T_(eff) = 7500 ± 110 K host star has M⋆ = 1.62^(+0.25)_(-0.20) M⊙ and R⋆ = 1.83 ± 0.10 R⊙. The planet has a radius of R_p = 1.91 ± 0.11 R_J and receives a stellar insolation flux of ~3.2 x 10^9 erg s^(-1) cm^(-2), leading to an inferred equilibrium temperature of T_(eq) ~ 1935 K assuming zero albedo and complete heat redistribution. With a ν sin I* = 84.8 ± 2.0 km s^(-1), the host is relatively slowly rotating compared to other stars with similar effective temperatures, and it appears to be enhanced in metallic elements but deficient in calcium, suggesting that it is likely an Am star. KELT-19A would be the first detection of an Am host of a transiting planet of which we are aware. Adaptive optics observations of the system reveal the existence of a companion with late-G9V/early-K1V spectral type at a projected separation of ≈160 au. Radial velocity measurements indicate that this companion is bound. Most Am stars are known to have stellar companions, which are often invoked to explain the relatively slow rotation of the primary. In this case, the stellar companion is unlikely to have caused the tidal braking of the primary. However, it may have emplaced the transiting planetary companion via the Kozai–Lidov mechanism.

Additional Information

© 2017 The American Astronomical Society. Received 2017 September 19; revised 2017 November 20; accepted 2017 November 27; published 2017 December 22. This project makes use of data from the KELT survey, including support from The Ohio State University, Vanderbilt University, and Lehigh University, along with the KELT follow-up collaboration. Work performed by J.E.R. was supported by the Harvard Future Faculty Leaders Postdoctoral fellowship. D.J.S. and B.S.G. were partially supported by NSF CAREER Grant AST-1056524. Work by S.V.Jr. is supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1343012. Work by G.Z. is provided by NASA through Hubble Fellowship grant HST-HF2-51402.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. This paper includes data taken at The McDonald Observatory of The University of Texas at Austin. This work has made use of NASA's Astrophysics Data System, the Extrasolar Planet Encyclopedia, the NASA Exoplanet Archive, the SIMBAD database operated at CDS, Strasbourg, France, and the VizieR catalog access tool, CDS, Strasbourg, France. We make use of Filtergraph, an online data visualization tool developed at Vanderbilt University through the Vanderbilt Initiative in Data-intensive Astrophysics (VIDA). We also used data products from the Widefield 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 European Space Agency (ESA) mission Gaia (http://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, http://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. MINERVA is a collaboration among the Harvard-Smithsonian Center for Astrophysics, The Pennsylvania State University, the University of Montana, and the University of New south Wales. MINERVA is made possible by generous contributions from its collaborating institutions and Mt. Cuba Astronomical Foundation, The David & Lucile Packard Foundation, National Aeronautics and Space Administration (EPSCOR grant NNX13AM97A), The Australian Research Council (LIEF grant LE140100050), and the National Science Foundation (grants 1516242 and 1608203). Any opinions, findings, and conclusions or recommendations expressed are those of the author and do not necessarily reflect the views of the National Science Foundation. This work was partially supported by funding from the Center for Exoplanets and Habitable Worlds. The Center for Exoplanets and Habitable Worlds is supported by the Pennsylvania State University, the Eberly College of Science, and the Pennsylvania Space Grant Consortium.

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