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

September 2015 • 2015ApJ...810...30F

Authors • Fulton, Benjamin J. • Collins, Karen A. • Gaudi, B. Scott • Stassun, Keivan G. • Pepper, Joshua • Beatty, Thomas G. • Siverd, Robert J. • Penev, Kaloyan • Howard, Andrew W. • Baranec, Christoph • Corfini, Giorgio • Eastman, Jason D. • Gregorio, Joao • Law, Nicholas M. • Lund, Michael B. • Oberst, Thomas E. • Penny, Matthew T. • Riddle, Reed • Rodriguez, Joseph E. • Stevens, Daniel J. • Zambelli, Roberto • Ziegler, Carl • Bieryla, Allyson • D'Ago, Giuseppe • DePoy, Darren L. • Jensen, Eric L. N. • Kielkopf, John F. • Latham, David W. • Manner, Mark • Marshall, Jennifer • McLeod, Kim K. • Reed, Phillip A.

Abstract • 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}_-55⁺⁵⁴ K, {log} g={4.078}_-0.054^+0.049, [{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 {M}_{{P}}={0.867}_-0.061^+0.065 M_J, radius {R}_{{P}}={1.86}_-0.16^+0.18 R_J, surface gravity {log} {g}_{{P}}={2.793}_-0.075^+0.072, and density {ρ }_{{P}}={0.167}_-0.038^+0.047 g cm^-3. The planet is on a roughly circular orbit with semimajor axis a={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.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2015ApJ...810...30F
• PDF https://iopscience.iop.org/article/10.1088/0004-637X/810/1/30/pdf
• PDF https://stacks.iop.org/0004-637X/810/30/pdf
• PREPRINT http://arxiv.org/abs/1505.06738
• DATA http://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-DisplayOverview?type=REFERENCE&bibcode=2015ApJ...810...30F
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2015ApJ...810...30F
• ELECTR https://doi.org/10.1088%2F0004-637X%2F810%2F1%2F30