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 \pm 0.07 ) G-type main sequence star with T _ { eff } = 5515 \pm 124 K. The amplitude of the RV-orbit yields a mass of the planet of 0.66 \pm 0.1 M _ { Jup } .
The planet has a radius of 0.96 \pm 0.06 R _ { Jup } and a mean bulk density of 0.9 \pm 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 _ { \oplus } within Kepler-15b .