The strong magnetic field of the large-amplitude β Cephei pulsator V1449 Aquilae

HUBRIG, S.; ILYIN, I.; BRIQUET, M.; SCHÖLLER, M.; GONZALEZ, J. F.; NUÑEZ, N.; DE CAT, P.; MOREL, T.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Año: 2011 vol. 531 p. 20 - 25

0004-6361

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 previousFORS 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 = 13. 893. 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 ξ 1 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.