Doppler Imaging of the Ap star ϵ Ursae Majoris: Ca, Cr, Fe, Mg, Mn, Ti, Sr

¹ Inst. for Astronomy, Univ. of Vienna, Türkenschanzstr. 17, 1180 Vienna, Austria e-mail: last_name@astro.univie.ac.at
² Department of Physics & Astronomy, Univ. British Columbia, Canada e-mail: kuschnig@astro.ubc.ca
³ Uppsala Astronomical Observatory, Box 515, 75120 Uppsala, Sweden e-mail: piskunov@astro.uu.se

Corresponding author: T. Lueftinger, lueftinger@astro.univie.ac.at

Received: 19 July 2001
Accepted: 20 May 2003

Abstract

The surface abundance structure of seven elements of the brightest chemically peculiar A-type star, ϵ Ursae Majoris (ϵ UMa, HD 112185, HR 4905) has been determined. Cr, Fe and, Mn are enhanced at the magnetic polar region of ϵ UMa while they avoid the magnetic equator. Sr seems to behave like Cr, Fe, and Mn, but is concentrated only at one of the two magnetic poles. Ti, in contrast, is accumulated at the magnetic equator and is depleted where Cr and Fe are accumulated, in accordance with theoretical predictions. Mg and Ca do not correlate with the distribution of Cr, Fe, Mn, and Sr or with Ti. The surface distribution of Mn, Sr, Ti, and Mg was determined for the first time for this star. A Doppler Imaging code was used that allows to analyse elements present in complex spectral line blends and thus to increase significantly the potential to map more elements. We compare our Cr and Fe distributions to already published maps. The high consistency of our results, based on different observations and Doppler Imaging codes, proves the reliability of the different methods.