Linear polarimetry of AP stars. II. New observations with a reappraisal of former ones.
Abstract
We have presented, in a previous paper, a canonical model which helps one to understand the intrinsic linear polarization measured in the light of magnetic Ap stars. This linear polarization, which provides a tracer of the magnetic field component perpendicular to the line of sight, can be observed in broad spectral regions, and it has been actually observed in several stars. Such measurements can provide useful information on the magnetism of Ap stars only when they sample correctly the whole rotation period of the object under study. Up to now, this condition had been fulfilled only in the case of HD 65339; in other cases, a more limited amount of data was available. Adding our new observations has enabled a first detailed analysis of HD 137909, HD 7 1866 and HD 115708; in particular, we can decide which of the angle i (between the line of sight and the rotation axis) and beta (between the rotation axis and the magnetic axis) is larger. Altogether, this paper contains a general review on all existing measurements and a comprehensive investigation on the linear polarization of four Ap stars based on previous observations and on our new measurements. The comparison of this observational material with the previously established model shows the capabilities and the limits of this method of study of Ap stars.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 1993
- Bibcode:
- 1993A&A...270..335L
- Keywords:
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- A Stars;
- Astronomical Polarimetry;
- Linear Polarization;
- Peculiar Stars;
- Stellar Magnetic Fields;
- Canonical Forms;
- Stellar Models;
- Astrophysics