Letter to the Editor

Rotational periods of four roAp stars^*

¹ Institute for Astronomy, University of Vienna, Türkenschanzstrasse 17, 1180 Wien, Austria e-mail: ryabchik@jan.astro.univie.ac.at
² Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya 48, 109017 Moscow, Russia
³ Physics Department, Royal Military College of Canada, Kingston, Ontario, K7K 7B4, Canada
⁴ Observatoire Midi Pyrénées, 57 avenue d'Azereix, BP 826, 65008 Tarbes Cedex, France
⁵ European Southern Observatory, Casilla 19001, Santiago 19, Chile
⁶ Observatoire Midi-Pyrénées, 14 avenue Édouard Belin, Toulouse, France
⁷ School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, KY16 9SS, UK
⁸ Department of Physics & Astronomy, The University of Western Ontario, London, Ontario, N6A 3K7, Canada
⁹ Institute of Astronomy, ETH-Zentrum, 8092 Zurich, Switzerland
¹⁰ Max-Planck Institut fuer Sonnensystemforschung Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany
¹¹ Department of Physics, Queen's University, Kingston, Ontario, Canada
¹² Deptartment of Astronomy, University of Minnesota, 116 Church St. S.E., Minneapolis, MN 55455, USA

Received: 8 November 2004
Accepted: 26 November 2004

Abstract

Forty-five new measurements of the mean longitudinal magnetic fields and mean equivalent widths of 4 roAp stars have obtained using the MuSiCoS spectropolarimeter at Pic du Midi observatory. These new high-precision data have been combined with archival measurements in order to constrain the rotational periods of HD 12098, HD 24712 = HR 1217, HD 122970 and HD 176232 = 10 Aql. We report a revised rotational period for HD 24712 ( ± 0.00016 d, crucial for interpretation of upcoming MOST observations of this star), new rotational periods for HD 12098 and HD 122970 ( ± 0.001 d and  ± 0.001 d, respectively) and evidence for an extremely long period for HD 176232.