KIC 4150611: a rare multi-eclipsing quintuple with a hybrid pulsator

Aims. We aim to analyse KIC 4150611 (HD 181469) - an interesting, bright quintuple system that includes a hybrid delta Sct/gamma Dor pulsator. Four periods of eclipses - 94.2, 8.65, 1.52 and 1.43 d - have been observed by the Kepler satellite, and three point sources (A, B, and C) are seen in high angular resolution images. Methods. From spectroscopic observations made with the HIDES spectrograph attached to the 1.88-m telescope of the Okayama Astrophysical Observatory (OAO), we have calculated for the first time radial velocities (RVs) of the component B - a pair of G-type stars - and combined them with Kepler photometry in order to obtain absolute physical parameters of this pair. We also managed to directly measure RVs of the pulsator, for the first time. Additionally, we modelled the light curves of the 1.52 and 1.43-day pairs, and measured their eclipse timing variations (ETVs). We also performed relative astrometry and photometry of three sources seen on the images taken with the NIRC2 camera of the Keck II telescope. Finally, we compared our results with theoretical isochrones. Results. The brightest component Aa is the hybrid pulsator, transited every 94.2 days by a pair of K/M-type stars (Ab1 + Ab2), which themselves form a 1.52-day eclipsing binary. The components Ba and Bb are late G-type stars, forming another eclipsing pair with a 8.65 day period. Their masses and radii are M-Ba = 0.894 +/- 0.010 M-circle dot, R-Ba = 0.802 +/- 0.044 R-circle dot for the primary, and M-Bb = 0.888 +/- 0.010 M-circle dot, R-Bb = 0.856 +/- 0.038 R-circle dot for the secondary. The remaining period of 1.43 days is possibly related to a faint third star C, which itself is most likely a background object. The system's properties are well-represented by a 35 Myr isochrone, basing on which the masses of the pulsator and the 1.52-day pair are M-Aa = 1.64(6) M-circle dot, and M-Ab,M-tot = 0.90(13) M-circle dot, respectively. There are also suggestions of additional bodies in the system.