Hubrig, S. ; Ilyin, I. ; Briquet, M. ; Schöller, M. ; González, J. F. ; Nuñez, N. ; De Cat, P. ; Morel, T.

published in Astronomy and Astrophysics, 531, pp. L20 (2011)

Abstract: Aims: Only for very few β Cephei stars has the behaviour of the magnetic field been studied over the rotation cycle. During the past two years we have obtained multi-epoch polarimetric spectra of the β Cephei star V1449 Aql with SOFIN at the Nordic Optical Telescope to search for a rotation period and to constrain the geometry of the magnetic field. Methods: The mean longitudinal magnetic field is measured at 13 different epochs. The new measurements, together with the previous FORS 1 measurements, have been used for the frequency analysis and the characterization of the magnetic field. Results: V1449 Aql so far possesses the strongest longitudinal magnetic field of up to 700 G among the β Cephei stars. The resulting periodogram displays three dominant peaks with the highest peak at f = 0.0720 d-1 corresponding to a period P = 13ḍ893. The magnetic field geometry can likely be described by a centred dipole with a polar magnetic field strength Bd around 3 kG and an inclination angle β of the magnetic axis to the rotation axis of 76 ± 4°. As of today, the strongest longitudinal magnetic fields are detected in the β Cephei stars V1449 Aql and ξ1 CMa with large radial velocity amplitudes. Their peak-to-peak amplitudes reach ~90 km s-1 and ~33 km s-1, respectively. Concluding, we briefly discuss the position of the currently known eight magnetic β Cephei and candidate β Cephei stars in the Hertzsprung-Russell (H-R) diagram. Based on observations obtained at the 2.56-m Nordic Optical Telescope on La Palma and ESO Prgs. 077.D-0311 and 178.D-0361.Appendix A is available in electronic form at http://www.aanda.org

DOI: 10.1051/0004-6361/201117261
Links: link