Kepler-15B: A Hot Jupiter Enriched in Heavy Elements and the First Kepler Mission Planet Confirmed With the Hobby-Eberly Telescope

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Date

2011-11

Authors

Endl, Michael
MacQueen, Phillip J.
Cochran, William D.
Brugamyer, Erik J.
Buchhave, Lars A.
Rowe, Jason
Lucas, Phillip
Isaacson, Howard
Bryson, Steve
Howell, Steve B.

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Abstract

We report the discovery of Kepler-15b (KOI-128), 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 RVs and 6 additional measurements from the Fibre-fed Echelle Spectrograph spectrograph at the Nordic Optical Telescope 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 semi-amplitude K of the RV orbit is 78.7(-9.5)(+ 8.5) m s(-1), which yields a planet mass 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 radius of Kepler-15b is smaller than the majority of transiting planets with similar mass and irradiation level. This suggests that the planet is more enriched in heavy elements than most other transiting giant planets. For Kepler-15b we estimate a heavy element mass of 30-40 M-circle plus.

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Endl, Michael, Phillip J. MacQueen, William D. Cochran, Erik J. Brugamyer, Lars A. Buchhave, Jason Rowe, Phillip Lucas et al. "Kepler-15b: A hot Jupiter enriched in heavy elements and the first Kepler Mission planet confirmed with the Hobby-Eberly telescope." The Astrophysical Journal Supplement Series, Vol. 197, No. 1 (Nov., 2011): 13.