Spectrum variability of ET Andromedae: SI and He surface mapping.
Abstract
ETAnd is a silicon star with a rotation period of 1.62d and the visible component of a binary system with an orbital period of 48.3d. We present abundance maps for silicon and helium, based on OHP-AURELIE spectra, and demonstrate that silicon and helium are concentrated in a belt-like structure along the magnetic equator. Surface regions with a silicon overabundance are correlated with helium underabundance. In the framework of diffusion theory, this pattern implies that a magnetic field configuration of ETAnd which favours the elevation of Si, simultaneously causes He to sink. In addition, we comment on the significance of Doppler mapping of CP stars for a correct abundance determination and on implications to pulsation mode identifications. We discuss our upper limit for short time-scale radial velocity variations of 1.4km/s, which contrasts to 4km/s, as was claimed in the literature with a period of 4.8^h^.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 1994
- Bibcode:
- 1994A&A...291..910P
- Keywords:
-
- Abundance;
- Astronomical Maps;
- Binary Stars;
- Helium;
- Peculiar Stars;
- Silicon;
- Variability;
- Line Spectra;
- Orbital Elements;
- Spectrum Analysis;
- Stellar Magnetic Fields;
- Stellar Rotation;
- Astronomy;
- STARS: CHEMICALLY PECULIAR;
- STARS: ACTIVITY;
- STARS: ET AND;
- STARS: IMAGING