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

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

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Año: 2011 vol. 531 p. 20 - 25

0004-6361

Aims. Only for very few ¥â 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 ¥â 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 ¥â 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 ¥â of the magnetic axis to the rotation axis of 76 ¡¾ 4◦ . As of today, the strongest longitudinal magnetic fields are detected in the ¥â Cephei stars V1449 Aql and ¥î 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 ¥â Cephei and candidate ¥â Cephei stars in the Hertzsprung-Russell (H-R) diagram.