The Chromaticity of Microlensing (Surface Imaging of Stars)

Gravitational microlensing is not achromatic when the star being microlensed is resolved by the lens. We show how narrow-band photometry and moderate- to high-resolution spectroscopy can be used to reconstruct the stellar surface intensity distribution of a microlensed star. Such microlens imaging can provide a unique opportunity to study the surfaces of normal red giants where Doppler imaging is not applicable due to slow rotation.}