Discovery of the magnetic field in the pulsating B star β Cephei
Context. Although the star itself is not helium enriched, the periodicity and the variability in the UV wind lines of the pulsating B1 IV star β Cephei are similar to what is observed in magnetic helium-peculiar B stars, suggesting that β Cep is magnetic. Aims. We searched for a magnetic field using...
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ftunivamstpubl:oai:uvapub:404332 2023-05-15T17:40:00+02:00 Discovery of the magnetic field in the pulsating B star β Cephei H.F. Henrichs J.A. de Jong E. Verdugo R.S. Schnerr C. Neiner J.-F. Donati C. Catala S.L.S. Shorlin G.A. Wade P.M. Veen J.S. Nichols E.M.F. Damen A. Talavera G.M. Hill L. Kaper A.M. Tijani V.C. Geers K. Wiersema B. Plaggenborg K.L.J. Rygl 2013 http://hdl.handle.net/11245/1.404332 en eng 10.1051/0004-6361/201321584 It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content licence (like Creative Commons). Astronomy & Astrophysics (00046361) vol.555 (2013) p.A46 article 2013 ftunivamstpubl 2016-08-24T22:14:01Z Context. Although the star itself is not helium enriched, the periodicity and the variability in the UV wind lines of the pulsating B1 IV star β Cephei are similar to what is observed in magnetic helium-peculiar B stars, suggesting that β Cep is magnetic. Aims. We searched for a magnetic field using high-resolution spectropolarimetry. From UV spectroscopy, we analysed the wind variability and investigated the correlation with the magnetic data. Methods. We used 130 time-resolved circular polarisation spectra that were obtained from 1998 (when β Cep was discovered to be magnetic) to 2005, with the MuSiCoS échelle spectropolarimeter at the 2 m Télescope Bernard Lyot. We applied the least-square deconvolution method on the Stokes V spectra and derived the longitudinal component of the integrated magnetic field over the visible hemisphere of the star. We performed a period analysis on the magnetic data and on equivalent-width measurements of UV wind lines obtained over 17 years. We also analysed the short- and long-term radial velocity variations, which are due to the pulsations and the 90-year binary motion, respectively. Results. β Cep hosts a sinusoidally varying magnetic field with an amplitude 97 ± 4 G and an average value − 6 ± 3 G. From the UV wind line variability, we derive a period of 12.00075(11) days, which is the rotation period of the star, and is compatible with the observed magnetic modulation. Phases of maximum and minimum field match those of maximum emission in the UV wind lines, strongly supporting an oblique magnetic-rotator model. We discuss the magnetic behaviour as a function of pulsation behaviour and UV line variability. Conclusions. This paper presents the analysis of the first confirmed detection of a dipolar magnetic field in an upper main-sequence pulsating star. Maximum wind absorption originates in the magnetic equatorial plane. Maximum emission occurs when the magnetic north pole points to the Earth. Radial velocities agree with the ~90-year orbit around its Be-star binary companion. Article in Journal/Newspaper North Pole Universiteit van Amsterdam: Digital Academic Repository (UvA DARE) North Pole |
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Open Polar |
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Universiteit van Amsterdam: Digital Academic Repository (UvA DARE) |
op_collection_id |
ftunivamstpubl |
language |
English |
description |
Context. Although the star itself is not helium enriched, the periodicity and the variability in the UV wind lines of the pulsating B1 IV star β Cephei are similar to what is observed in magnetic helium-peculiar B stars, suggesting that β Cep is magnetic. Aims. We searched for a magnetic field using high-resolution spectropolarimetry. From UV spectroscopy, we analysed the wind variability and investigated the correlation with the magnetic data. Methods. We used 130 time-resolved circular polarisation spectra that were obtained from 1998 (when β Cep was discovered to be magnetic) to 2005, with the MuSiCoS échelle spectropolarimeter at the 2 m Télescope Bernard Lyot. We applied the least-square deconvolution method on the Stokes V spectra and derived the longitudinal component of the integrated magnetic field over the visible hemisphere of the star. We performed a period analysis on the magnetic data and on equivalent-width measurements of UV wind lines obtained over 17 years. We also analysed the short- and long-term radial velocity variations, which are due to the pulsations and the 90-year binary motion, respectively. Results. β Cep hosts a sinusoidally varying magnetic field with an amplitude 97 ± 4 G and an average value − 6 ± 3 G. From the UV wind line variability, we derive a period of 12.00075(11) days, which is the rotation period of the star, and is compatible with the observed magnetic modulation. Phases of maximum and minimum field match those of maximum emission in the UV wind lines, strongly supporting an oblique magnetic-rotator model. We discuss the magnetic behaviour as a function of pulsation behaviour and UV line variability. Conclusions. This paper presents the analysis of the first confirmed detection of a dipolar magnetic field in an upper main-sequence pulsating star. Maximum wind absorption originates in the magnetic equatorial plane. Maximum emission occurs when the magnetic north pole points to the Earth. Radial velocities agree with the ~90-year orbit around its Be-star binary companion. |
format |
Article in Journal/Newspaper |
author |
H.F. Henrichs J.A. de Jong E. Verdugo R.S. Schnerr C. Neiner J.-F. Donati C. Catala S.L.S. Shorlin G.A. Wade P.M. Veen J.S. Nichols E.M.F. Damen A. Talavera G.M. Hill L. Kaper A.M. Tijani V.C. Geers K. Wiersema B. Plaggenborg K.L.J. Rygl |
spellingShingle |
H.F. Henrichs J.A. de Jong E. Verdugo R.S. Schnerr C. Neiner J.-F. Donati C. Catala S.L.S. Shorlin G.A. Wade P.M. Veen J.S. Nichols E.M.F. Damen A. Talavera G.M. Hill L. Kaper A.M. Tijani V.C. Geers K. Wiersema B. Plaggenborg K.L.J. Rygl Discovery of the magnetic field in the pulsating B star β Cephei |
author_facet |
H.F. Henrichs J.A. de Jong E. Verdugo R.S. Schnerr C. Neiner J.-F. Donati C. Catala S.L.S. Shorlin G.A. Wade P.M. Veen J.S. Nichols E.M.F. Damen A. Talavera G.M. Hill L. Kaper A.M. Tijani V.C. Geers K. Wiersema B. Plaggenborg K.L.J. Rygl |
author_sort |
H.F. Henrichs |
title |
Discovery of the magnetic field in the pulsating B star β Cephei |
title_short |
Discovery of the magnetic field in the pulsating B star β Cephei |
title_full |
Discovery of the magnetic field in the pulsating B star β Cephei |
title_fullStr |
Discovery of the magnetic field in the pulsating B star β Cephei |
title_full_unstemmed |
Discovery of the magnetic field in the pulsating B star β Cephei |
title_sort |
discovery of the magnetic field in the pulsating b star β cephei |
publishDate |
2013 |
url |
http://hdl.handle.net/11245/1.404332 |
geographic |
North Pole |
geographic_facet |
North Pole |
genre |
North Pole |
genre_facet |
North Pole |
op_source |
Astronomy & Astrophysics (00046361) vol.555 (2013) p.A46 |
op_relation |
10.1051/0004-6361/201321584 |
op_rights |
It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content licence (like Creative Commons). |
_version_ |
1766140768049692672 |