Mapping of stellar surfaces with Doppler and Zeeman-Doppler imaging

Doppler imaging has been used to image dark spots on the surfaces of rapidly rotating, magnetically active stars for the last 20 years. More recently, methods have been developed for combining line-profile information from large numbers of spectral lines simultaneously. This has allowed starspot distributions to be mapped in sufficient detail to allow tracking of individual spots over several stellar rotations, delineating surface differential rotation patterns for a number of stars. Zeeman-Doppler imaging allows the creation of stellar magnetograms; which are providing the first insights into the 3D topology of stellar coronal magnetic fields. The advent of cryogenic infrared echelle spectrographs opens up exciting new possibilities for Doppler imaging in molecular lines of species such as TiO, OH, and FeH.