KIC 11401845: An Eclipsing Binary with Multiperiodic Pulsations and Light-travel Time

We report the {\text{}}{Kepler} photometry of KIC 11401845 displaying multiperiodic pulsations, superimposed on binary effects. Light-curve synthesis shows that the binary star is a short-period detached system with a very low mass ratio of q = 0.070 and filling factors of F₁ = 45% and F₂ = 99%. Multiple-frequency analyses were applied to the light residuals after subtracting the synthetic eclipsing curve from the observed data. We detected 23 frequencies with signal-to-noise ratios larger than 4.0, of which the orbital harmonics (f₄, f₆, f₉, f₁₅) in the low-frequency domain may originate from tidally excited modes. For the high frequencies of 13.7-23.8 day^-1, the period ratios and pulsation constants are in the ranges of {P}_{pul}/{P}_{orb}=0.020{--}0.034 and Q = 0.018-0.031 days, respectively. These values and the position on the Hertzsprung-Russell diagram demonstrate that the primary component is a δ Sct pulsating star. We examined the eclipse timing variation of KIC 11401845 from the pulsation-subtracted data and found a delay of 56 ± 17 s in the arrival times of the secondary eclipses relative to the primary eclipses. A possible explanation of the time shift may be some combination of a light-travel-time delay of about 34 s and a very small eccentricity of e\cos ω < 0.0002. This result represents the first measurement of the Rømer delay in noncompact binaries.