Summary: Astronomy & Astrophysics manuscript no. RRKolBagfinal c ESO 2009
February 10, 2009
Observational constraints on the magnetic field of RR Lyrae stars
Katrien Kolenberg1 and Stefano Bagnulo2
Institut fuer Astronomie, Universitaet Wien, Tuerkenschanzstrasse 17, A-1018 Wien, Austria.
Armagh Observatory, College Hill, Armagh BT61 9DG, U.K. e-mail: email@example.com
Received: 2008-12-24 / Accepted: 2009-1-30
Context. A high percentage of the astrophysically important RR Lyrae stars show a periodic amplitude and/or phase modulation of
their pulsation cycles. More than a century after its discovery, this "Blazhko effect" still lacks acceptable theoretical understanding.
In one of the plausible models for explaining the phenomenon, the modulation is caused by the effects of a magnetic field. So far, the
available observational data have not allowed us to either support nor rule out the presence of a magnetic field in RR Lyrae stars.
Aims. We intend to determine whether RR Lyrae stars are generally characterized by the presence of a magnetic field organized on a
Methods. With the help of the FORS1 instrument at the ESO VLT we performed a spectropolarimetric survey of 17 relatively bright
southern RR Lyrae stars, both Blazhko stars and non-modulated stars, and determined their mean longitudinal magnetic field with a
typical error bar < 30 G.