Cool Stars 14 - Submitted Abstract # 58
This version created on 05 October 2006

Multi-line Doppler imaging:  getting the most out of your echelle


John B. Rice, Brandon University, Canada 
Klaus G. Strassmeier, Astrophysical Institute Potsdam, Germany

The advent of spectroscopic observing facilities producing large
numbers of observations covering many lines in a single exposure
requires that we develop Doppler Imaging techniques for working with
many lines simultaneously.  One possibility would be averaging
together many lines to get a ``meanТТ line to analyze but we would
thus lose the information necessary to actually recover a surface
temperature map.  Alternatively, we could work with large numbers of
lines simultaneously by synthesizing long segments of the stellar
spectrum and mapping with the whole spectrum.  Experiments have shown
this dilutes the information in the profiles of the ``good'' lines to
the point where little sensitivity to the surface temperature map is
left.  The alternative proposed here is to work with numerous good
lines extracted from the spectrum with the continuum and weak line
sections removed.  In this way we can retain the dependence on
individual line synthesis using LTE assumptions and adopting atomic
data from VALD so that the maps retain the effective surface
temperature information.  The map parameters are determined by relying
on refining the input parameters through minimization of the fit to
the full array of lines.  We present here a small-scale comparative
test of the mapping of the young K dwarf PW Andromedae using several
Fe lines chosen from CFHT Gecko observations made in the year 2004.

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