Stars with Discrepant v sin i as Derived from the Ca II 3933 and Mg II 4481 Å Lines
Abstract
Axial rotation of a star plays an important role in its evolution, physical conditions in its atmosphere and the shape of its spectrum. Methods of determining v sin i are based on comparison of the observed profiles of spectral lines with the theoretical ones. Their accuracy depends on the type and quality of spectrograms, as well as on the algorithms used. A frequently used method is a simple comparison of one line, e.g. the Ca II at 3933 Å or Mg II at 4481 Å. This, however, may result in a false value of v sin i in the case when low-dispersion spectra are used. We investigate the spectra of stars with a significant discrepancy of their rotational velocities introduced in various sources, and analyze the corresponding spectral region from the point of view of possible admixed features, which may mask the true line profiles. We use the CCD spectra of the stars having this discrepancy to compare with theoretical spectra. We also studied the photographic spectra, obtained during the 1970s and 1980s.
- Publication:
-
Magnetic Stars
- Pub Date:
- 2011
- Bibcode:
- 2011mast.conf..410Z