Rotation, pulsations and magnetic field in V 2052 Ophiuchi: A new He-strong star ^*,**

¹ Sterrenkundig Instituut “Anton Pannekoek”, Universiteit van Amsterdam, The Netherlands
² GEPI/UMR 8111 du CNRS, Observatoire de Paris-Meudon, France
³ Current affiliation: RSSD, Estec / ESA, Keplerlaan 1, 2201 AZ, Noordwijk ZH, The Netherlands
⁴ Max Planck Institut für Aeronomie, Lindau, Germany
⁵ Harvard/Smithsonian Center for Astrophysics, Cambridge, MA, USA
⁶ Observatoire de la Côte d'Azur, France
⁷ Astronomical Observatory Beograd, Yugoslavia

Corresponding author: C. Neiner, cneiner@rssd.esa.int

Received: 13 August 2002
Accepted: 19 August 2003

Abstract

V 2052 Oph is a β Cep star with km s^-1. The behavior of its stellar wind was studied in the ultraviolet wavelength region with the IUE satellite. It revealed periodic variations in the equivalent widths (EW) of the resonance lines of wind-sensitive ions with a period of 3.638833 d, which is identified as the rotational period. These variations are typical of magnetic stars. Therefore time-resolved circular spectropolarimetric observations were obtained with the Musicos échelle spectropolarimeter at the 2-m Télescope Bernard Lyot (TBL) to search for a magnetic field in the star. Stokes V patterns were observed, the inclination and magnetic angles were derived and a value was determined for the polar magnetic field ( G) using an oblique rotator dipole model. The spectroscopic information was used to search for periodicity in line-profile variations (lpv), radial velocity and minimum intensity curves. Multiperiodicity was found, corresponding to radial ( c d^-1) and non-radial ( c d^-1, or 4) pulsation modes. The rotation period is also detected in rotationally modulated observables because of the magnetic poles passing through the observer's line of sight. We determined the stellar parameters of the star, which was found to be chemically peculiar, in particular He-enriched. This makes V 2052 Oph the first magnetic He-strong early B star with known pulsational properties.