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Interferometric-Doppler imaging of stellar surface abundances

Similarly as the technique of Doppler Imaging from spectroscopic observations, Differential Interferometry makes it possible to measure the disturbances of photocentroid location of an unresolved star as a function of wavelength and to deduce the corresponding stellar map. We show the imaging potential of a tomographic technique which combines time-resolved spectroscopy and long baseline interferometry, providing information that cannot be obtained otherwise with each of these techniques taken at once. In particular, here we consider the example of mapping abundance inhomogeneities, performing numerical experiments with realistic spectral resolutions and signal-to-noise ratios expected for operating (VLTI, GI2T) or close-to-operating long baseline interferometers (Chara, Keck). We show that the accurate maps of stellar surface abundance distribution can be obtained using regularized inversion by Maximum Entropy method. The technique is also applicable to other classes of stellar surface imaging as magnetic field and temperature spots but within the classical instrumental context (without polarimetric device) it can hardly discriminate among different distributions. We discuss the importance of Spectro-Polarimetric Interferometry observations (Rousselet-Perraut et al., this proceedings) in order to discriminate and simultaneously map abundance/temperature inhomogeneities and magnetic fields of chemically peculiar (CP) stars.