Late-type stars in general possess complicated magnetic surface fields which
makes their detection and in particular their modeling and reconstruction
challenging. In this work we present a new Zeeman-Doppler imaging code which is
especially designed for the application to late-type stars. This code uses a
new multi-line cross-correlation technique by means of a principal component
analysis to extract and enhance the quality of individual polarized line
profiles. It implements the full polarized radiative transfer equation and uses
an inversion strategy that can incorporate prior knowledge based on solar
analogies. Moreover, our code utilizes a new regularization scheme which is
based on local maximum entropy to allow a more appropriate reproduction of
complex surface fields as those expected for late-type stars. In a first
application we present Zeeman-Doppler images of II Pegasi which reveal a
surprisingly large scale surface structure with one predominant (unipolar)
magnetic longitude which is mainly radially oriented.Comment: Astronomische Nachrichten / Astronomical Notes Vol. 328, Issue 10, p.
104