Eclipse mapping of Algol-type systems with oscillating δ Scuti type components

Abstract

The oscillating Algol-type (oEA) stars are the former secondaries of evolved, semi-detached eclipsing binaries which are (still) undergoing mass transfer and form a newly detected class of pulsators close to the main sequence. Their unique feature consists of mass accretion onto the atmosphere of the pulsating star. Mass accretion affects the mass, radius, density as well as the star’s evolution. Such stars are therefore very attractive targets for asteroseismic studies. A new tool for mode identification of pulsating components in eclipsing binaries consists in using the event of primary eclipse as a spatial filter to resolve the pulsations across the stellar surface of the pulsator. During an eclipse, depending on the spatial structure of modes represented by the wave numbers (l,m), different shapes of the pulsation amplitude and phase variations can be observed. A comparison between the modelled and the observed amplitudes and phases then provides the correct mode identification. The method needs a geometrical model, the pulsation frequencies and the light curves as input. The geometrical model can be obtained from a simultaneous modelling of the light and radial velocity curves. The pulsation frequencies are obtained from subtracting a binary model from the original light curves followed by a frequency analysis of the residuals. We will identify and illustrate systems where observations with a fast CCD camera equipping the 3.6-m DOT telescope could deliver the data needed for the application of the eclipse mapping method.