KIC 11285625: A double-lined spectroscopic binary with a γ Doradus pulsator discovered from Kepler space photometry

Aims. We present the first binary modelling results for the pulsating, eclipsing binary KIC 11285625 that was discovered by the Kepler mission. An automated method to disentangle the pulsation spectrum and the orbital variability in high quality light curves was developed and applied. The goal was to obtain accurate orbital and component properties in combination with essential information derived from spectroscopy. Methods. A binary model for KIC 11285625 was obtained, using a combined analysis of high-quality space-based Kepler light curves and ground-based high-resolution HERMES echelle spectra. The binary model was used to separate the pulsation characteristics from the orbital variability in the Kepler light curve in an iterative way. We used an automated procedure based on the JKTEBOP binary modelling code to perform this task, and adapted codes for frequency analysis and prewhitening of periodic signals. Using a disentangling technique applied to the composite HERMES spectra, we obtained a higher signal-to-noise mean spectrum for both the primary and the secondary components. A model grid search method for fitting synthetic spectra was used for fundamental parameter determination for both components. Results. Accurate orbital and component properties of KIC 11285625 were derived, and we have obtained the pulsation spectrum of the gamma Dor pulsator in the system. Detailed analysis of the pulsation spectrum revealed amplitude modulation on a timescale of a hundred days, and strong indications of frequency splittings at both the orbital frequency and the rotational frequency derived from spectroscopy.