The beaming effect (aka Doppler boosting) induces a variation in the observedflux of a luminous object, following its observed radial velocity variation. Wedescribe a photometric signal induced by the beaming effect during eclipse ofbinary systems, where the stellar components are late type Sun-like stars. Theshape of this signal is sensitive to the angle between the eclipsed star's spinaxis and the orbital angular momentum axis, thereby allowing its measurement.We show that during eclipse there are in fact two effects, superimposed on theknown eclipse light curve. One effect is produced by the rotation of theeclipsed star, and is the photometric analog of the spectroscopicRossiter-McLaughlin effect, thereby it contains information about thesky-projected spin-orbit angle. The other effect is produced by the varyingweighted difference, during eclipse, between the beaming signals of the twostars. We give approximated analytic expressions for the amplitudes of the twoeffects, and present a numerical simulation where we show the light curves forthe two effects for various orbital orientations, for a low mass ratio stellareclipsing binary system. We show that although the overall signal is small, itcan be detected in the primary eclipse when using Kepler Long Cadence data ofbright systems accumulated over the mission lifetime.
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