EDP Sciences
Free access
Volume 413, Number 3, January III 2004
Page(s) 1087 - 1093
Section Formation and evolution of planetary systems
DOI http://dx.doi.org/10.1051/0004-6361:20031600

A&A 413, 1087-1093 (2004)
DOI: 10.1051/0004-6361:20031600

No evidence of a strong magnetic field in the Blazhko star RR Lyrae

M. Chadid1, G. A. Wade2, S. L. S. Shorlin3 and J. D. Landstreet3

1  Observatoire de la côte d'Azur, UMR 6528, BP 4229, 06304 Nice Cedex 04, France
2  Department of Physics, Royal Military College of Canada, PO Box 17000, Station "Forces", Kingston, Ontario, Canada K7K 4B4
3  Department of Physics & Astronomy, the University of Western Ontario, London, Ontario, Canada N6A 3K7

(Received 9 April 2003 / Accepted 9 October 2003 )

In this paper we report a new series of high-precision (median $\sigma_{\rm B}\sim 80$ G) longitudinal magnetic field measurements of RR Lyrae, the brightest Blazhko star, obtained with the MuSiCoS spectropolarimeter over a period of almost 4 years from 1999-2002. These data provide no evidence whatsoever for a strong magnetic field in the photosphere of RR Lyrae, a result consistent with Preston's (1967) results, but inconsistent with apparent magnetic field detections by Babcock (1958) and Romanov et al. (1987, 1994). Following discussion of these disparate results, we conclude that RR Lyrae is a bona fide non-magnetic star, a conclusion which leads to the general falsification of models of the Blazkho effect requiring strong photospheric magnetic fields. Furthermore, due to the 4 year baseline of our observations, we can also dismiss the hypothesis that RR Lyrae undergoes a 4-year "magnetic cycle". Therefore the origin of the observed 4-year modulation of RR Lyrae remains unexplained, and we stress the need for additional theoretical efforts to come to a better understanding of this phenomenon.

Key words: stars: variables: RR Lyr -- stars: oscillations -- stars: magnetic fields -- stars: individual: RR Lyrae -- techniques: spectroscopic, polarimetric

Offprint request: M. Chadid, chadid@obs-nice.fr

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