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KELT-8b: A Highly Inflated Transiting Hot Jupiter and a New Technique for Extracting High-precision Radial Velocities from Noisy Spectra

Fulton, Benjamin J. and Howard, Andrew W. and Riddle, Reed (2015) KELT-8b: A Highly Inflated Transiting Hot Jupiter and a New Technique for Extracting High-precision Radial Velocities from Noisy Spectra. Astrophysical Journal, 810 (1). Art. No. 30. ISSN 0004-637X.

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We announce the discovery of a highly inflated transiting hot Jupiter by the KELT-North survey. A global analysis including constraints from isochrones indicates that the V = 10.8 host star (HD 343246) is a mildly evolved, G dwarf with T_(eff)= 5754^(+54)_(-55)K, log g = 4.078^(0.049)_(0.054), [Fe/H] = 0.272 ± 0.038, an inferred mass M_* = 1.211_(0.066)^(+0.078)M_☉, and radius R_*=1.67 _(-0.12)^(+0.14) R_☉. The planetary companion has a mass Mp = 0.867 _(-0.061)^+(0.065) MJ, radius R_p 1.86_(-0.16)^(+0.18) R_J, surface gravity log g_p 2.793_(-0.075)^(+0.072), and density 0.167_(-0.038)^(+0.047) g cm^(−3). The planet is on a roughly circular orbit with semimajor axis ɑ 0.04571_(0.00084)^(+0.00096) AU and eccentricity e 0.035_(-0.025)^(+0.050). The best-fit linear ephemeris is T_0 = 2456883.4803 ± 0.0007 BJD_(TDB) and P = 3.24406 ± 0.00016 days. This planet is one of the most inflated of all known transiting exoplanets, making it one of the few members of a class of extremely low density, highly irradiated gas giants. The low stellar log g and large implied radius are supported by stellar density constraints from follow-up light curves, as well as an evolutionary and space motion analysis. We also develop a new technique to extract high-precision radial velocities from noisy spectra that reduces the observing time needed to confirm transiting planet candidates. This planet boasts deep transits of a bright star, a large inferred atmospheric scale height, and a high equilibrium temperature of T_(eq) 1675_(-55)^(+61)K, assuming zero albedo and perfect heat redistribution, making it one of the best targets for future atmospheric characterization studies.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Fulton, Benjamin J.0000-0003-3504-5316
Howard, Andrew W.0000-0001-8638-0320
Riddle, Reed0000-0002-0387-370X
Additional Information:© 2015 The American Astronomical Society. Received 2015 May 25; accepted 2015 July 24; published 2015 August 26. We would like to dedicate this paper to the memory of our partner and collaborator, Giorgio Corfini, who contributed to this discovery and passed away in 2014. We thank the many observers who contributed to the measurements reported here. The Robo-AO system was developed by collaborating partner institutions, the California Institute of Technology and the Inter-University Centre for Astronomy and Astrophysics, and with the support of the National Science Foundation under grant Nos. AST-0906060, AST-0960343, and AST-1207891; the Mt. Cuba Astronomical Foundation; and by a gift from Samuel Oschin. Ongoing science operation support of Robo-AO is provided by the California Institute of Technology and the University of Hawai'i. C.B. acknowledges support from the Alfred P. Sloan Foundation. This material is based upon 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. Work by T.G.B., B.S.G., and D.J.S. was partially supported by NSF CAREER grant AST-1056524 . K.P. acknowledges support from NASA grant NNX13AQ62. G.D. acknowledges Regione Campania, POR FSE 2007-13. This work made use of the SIMBAD database (operated at CDS, Strasbourg, France), NASA's Astrophysics Data System Bibliographic Services, and the NASA Star and Exoplanet Database (NStED). This research made use of the Exoplanet Orbit Database and the Exoplanet Data Explorer at This research also made use of the Washington Double Star Catalog maintained at the U.S. Naval Observatory. Finally, the authors wish to extend special thanks to those of Hawai'ian ancestry on whose sacred mountain of Maunakea we are privileged to be guests. Without their generous hospitality, the Keck observations presented herein would not have been possible.
Funding AgencyGrant Number
Mt. Cuba Astronomical FoundationUNSPECIFIED
University of HawaiiUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
NSF Graduate Research Fellowship2014184874
Regione CampaniaPOR FSE 2007-13
Subject Keywords:planetary systems, stars: individual (HD 343246)
Issue or Number:1
Record Number:CaltechAUTHORS:20151027-102855317
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Official Citation:KELT-8b: A Highly Inflated Transiting Hot Jupiter and a New Technique for Extracting High-precision Radial Velocities from Noisy Spectra Benjamin J. Fulton et al. 2015 ApJ 810 30
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:61553
Deposited By: Ruth Sustaita
Deposited On:27 Oct 2015 22:40
Last Modified:03 Oct 2019 09:09

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