The First Kepler Mission Planet Confirmed With The Hobby-Eberly Telescope: Kepler-15b, a Hot Jupiter Enriched In Heavy Elements
astro-ph.EP
/ Authors
Michael Endl, Phillip J. MacQueen, William D. Cochran, Erik Brugamyer, Lars A. Buchhave, Jason Rowe, Phillip Lucas, Howard Issacson, Steve Bryson, Steve B. Howell
and 23 more authors
Jonathan J. Fortney, Terese Hansen, William J. Borucki, Douglas Caldwell, Jessie L. Christiansen, David R. Ciardi, Brice-Olivier Demory, Mark Everett, Eric B. Ford, Michael R. Haas, Matthew J. Holman, Elliot Horch, Jon M. Jenkins, David J. Koch, Jack J. Lissauer, Pavel Machalek, Martin Still, William F. Welsh, Dwight T. Sanderfer, Shawn E. Seader, Jeffrey C. Smith, Susan E. Thompson
/ Abstract
We report the discovery of Kepler-15b, a new transiting exoplanet detected by NASA's Kepler mission. The transit signal with a period of 4.94 days was detected in the quarter 1 (Q1) Kepler photometry. For the first time, we have used the High-Resolution-Spectrograph (HRS) at the Hobby-Eberly Telescope (HET) to determine the mass of a Kepler planet via precise radial velocity (RV) measurements. The 24 HET/HRS radial velocities (RV) and 6 additional measurements from the FIES spectrograph at the Nordic Optical Telescope (NOT) reveal a Doppler signal with the same period and phase as the transit ephemeris. We used one HET/HRS spectrum of Kepler-15 taken without the iodine cell to determine accurate stellar parameters. The host star is a metal-rich ([Fe/H]=0.36+/-0.07) G-type main sequence star with T_eff=5515+/-124 K. The amplitude of the RV-orbit yields a mass of the planet of 0.66+/-0.1 M_Jup. The planet has a radius of 0.96+/-0.06 R_Jup and a mean bulk density of 0.9+/-0.2 g/cm^3. The planetary radius resides on the lower envelope for transiting planets with similar mass and irradiation level. This suggests significant enrichment of the planet with heavy elements. We estimate a heavy element mass of 30-40 M_Earth within Kepler-15b.