[en] We present extensive optical spectroscopy of the early-type magnetic star HD 191612 (O6.5f ? pe-O8fp). The Balmer and He i lines show strongly variable emission which is highly reproducible on a well-determined 538-d period. He ii absorptions and metal lines (including many selective emission lines but excluding He ii lambda 4686 angstrom emission) are essentially constant in line strength, but are variable in velocity, establishing a double-lined binary orbit with P-orb = 1542 d, e = 0.45. We conduct a model-atmosphere analysis of the spectrum, and find that the system is consistent with a similar to O8 giant with a similar to B1 main-sequence secondary. Since the periodic 538-d changes are unrelated to orbital motion, rotational modulation of a magnetically constrained plasma is strongly favoured as the most likely underlying 'clock'. An upper limit on the equatorial rotation is consistent with this hypothesis, but is too weak to provide a strong constraint.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Howarth, Ian D.
Walborn, Nolan R.
Lennon, Danny J.
Puls, Joachim
Nazé, Yaël ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE)
Annuk, K.
Antokhin, I.
Bohlender, D.
Bond, H.
Donati, J. F.
Georgiev, L.
Gies, D.
Harmer, D.
Herrero, A.
Kolka, I.
McDavid, D.
Morel, Thierry ; Katholieke Universiteit Leuven, Departement Natuurkunde en Sterrenkunde, Instituut voor Sterrenkunde, Celestijnenlaan 200D, 3001 Leuven, Belgium
Negueruela, I.
Rauw, Grégor ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE)
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