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KELT-6b: A P ~ 7.9 Day Hot Saturn Transiting a Metal-poor Star with a Long-period Companion

Collins, Karen A. and Johnson, John Asher and Howard, Andrew W. and Hinkley, Sasha and Fulton, Benjamin J. (2014) KELT-6b: A P ~ 7.9 Day Hot Saturn Transiting a Metal-poor Star with a Long-period Companion. Astronomical Journal, 147 (2). Art. No. 39. ISSN 0004-6256. https://resolver.caltech.edu/CaltechAUTHORS:20140218-082654422

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Abstract

We report the discovery of KELT-6b, a mildly inflated Saturn-mass planet transiting a metal-poor host. The initial transit signal was identified in KELT-North survey data, and the planetary nature of the occulter was established using a combination of follow-up photometry, high-resolution imaging, high-resolution spectroscopy, and precise radial velocity measurements. The fiducial model from a global analysis including constraints from isochrones indicates that the V = 10.38 host star (BD+31 2447) is a mildly evolved, late-F star with T_(eff_ = 6102 ± 43 K,_log g_* =4.07_(-0.07)^(+0.04), and [Fe/H] = –0.28 ± 0.04, with an inferred mass M_* = 1.09 ± 0.04 M_☉ and radius R_* =1.58_(-0.09)^(+0.16) ,R_☉. The planetary companion has mass M_P = 0.43 ± 0.05 M_(Jup), radius R_p =1.19_(-0.08)^(+0.13),R_(Jup), surface gravity g_p = 2.86_(-0.08)^(+0.06), and density P_p = 0.31_(-0.08)^(+0.07), cm^(-3). The planet is on an orbit with semimajor axis ɑ = 0.079 ± 0.001 AU and eccentricity e = 0.22_(-0.10)^(+0.12), which is roughly consistent with circular, and has ephemeris of T_c(BJD_(TDB)) = 2456347.79679 ± 0.00036 and P = 7.845631 ± 0.000046 days. Equally plausible fits that employ empirical constraints on the host-star parameters rather than isochrones yield a larger planet mass and radius by ~4}-7}. KELT-6b has surface gravity and incident flux similar to HD 209458b, but orbits a host that is more metal poor than HD 209458 by ~0.3 dex. Thus, the KELT-6 system offers an opportunity to perform a comparative measurement of two similar planets in similar environments around stars of very different metallicities. The precise radial velocity data also reveal an acceleration indicative of a longer-period third body in the system, although the companion is not detected in Keck adaptive optics images.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://iopscience.iop.org/1538-3881/147/2/39/PublisherArticle
http://dx.doi.org/10.1088/0004-6256/147/2/39DOIArticle
http://arxiv.org/abs/1308.2296arXivDiscussion Paper
ORCID:
AuthorORCID
Collins, Karen A.0000-0001-6588-9574
Johnson, John Asher0000-0001-9808-7172
Howard, Andrew W.0000-0001-8638-0320
Hinkley, Sasha0000-0001-8074-2562
Fulton, Benjamin J.0000-0003-3504-5316
Additional Information:© 2014 American Astronomical Society. Received 2013 September 16; accepted 2013 November 22; published 2014 January 10. K.A.C. was supported by a NASA Kentucky Space Grant Consortium Graduate Fellowship. Early work on KELT-North was supported by NASA Grant NNG04GO70G. J.A.P. and K.G.S. acknowledge support from the Vanderbilt Office of the Provost through the Vanderbilt Initiative in Data-intensive Astrophysics. E.L.N.J. gratefully acknowledges the support of the National Science Foundation’s PREST program, which helped to establish the Peter van de Kamp Observatory through grant AST-0721386. K.G.S. acknowledges the support of the National Science Foundation through PAARE Grant AST-0849736 and AAG Grant AST-1009810. Work by B.S.G. and T.G.B. was partially supported by NSF CAREER Grant AST-1056524. K.P. acknowledges support from NASA grant NNX09AB29G and NSF award number 1108686. We thank the anonymous referee for a thoughtful reading of the manuscript and for useful suggestions. We thank Geoff Marcy and Howard Isaacson for Keck HIRES observations, calibration, and reduction of spectra to 1D form. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. The TRES and KeplerCam observations were obtained with partial support from the Kepler Mission through NASA Cooperative Agreement NNX11AB99A with the Smithsonian Astrophysical Observatory (PI: D.W.L.). A portion of this work was supported by the National Science Foundation under grant Nos. AST-1203023. We thank Roberto Zambelli of Societa Astronomica Lunae for participation in the KELT followup network. This work has made use of NASA’s Astrophysics Data System, the Exoplanet Orbit Database at exoplanets.org, the Extrasolar Planet Encyclopedia at exoplanet.eu (Schneider et al. 2011), the SIMBAD database operated at CDS, Strasbourg, France, and Systemic (Meschiari et al. 2009). KELT is a joint project of The Ohio State University, Vanderbilt University, and Lehigh University.
Funders:
Funding AgencyGrant Number
Kentucky Space Grant ConsortiumUNSPECIFIED
NASANNG04GO70G
Vanderbilt UniversityUNSPECIFIED
NSFAST-0721386
NSFAST-0849736
NSFAST-1009810
NSFAST-1056524
NASANNX09AB29G
NSFAST-1108686
NASANNX11AB99A
NSFAST-1203023
Subject Keywords:instrumentation: adaptive optics; planetary systems; stars: individual (KELT-6, BD+31 2447, TYC 2532-556-1, HD 209458); techniques: photometric; techniques: spectroscopic
Issue or Number:2
Record Number:CaltechAUTHORS:20140218-082654422
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140218-082654422
Official Citation:KELT-6b: A P ~ 7.9 Day Hot Saturn Transiting a Metal-poor Star with a Long-period Companion Karen A. Collins et al. 2014 The Astronomical Journal 147 39
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43846
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:18 Feb 2014 18:10
Last Modified:09 Mar 2020 13:18

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