Article (Scientific journals)
B fields in OB stars (BOB): low-resolution FORS2 spectropolarimetry of the first sample of 50 massive stars
Fossati, L.; Castro, N.; Schoeller, M. et al.
2015In Astronomy and Astrophysics, 582, p. 750
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Keywords :
Astrophysics - Solar and Stellar Astrophysics
Abstract :
[en] Within the context of the collaboration "B fields in OB stars (BOB)", we used the FORS2 low-resolution spectropolarimeter to search for a magnetic field in 50 massive stars, including two reference magnetic massive stars. Because of the many controversies of magnetic field detections obtained with the FORS instruments, we derived the magnetic field values with two completely independent reduction and analysis pipelines. We compare and discuss the results obtained from the two pipelines. We obtained a general good agreement, indicating that most of the discrepancies on magnetic field detections reported in the literature are caused by the interpretation of the significance of the results (i.e., 3-4 sigma detections considered as genuine, or not), instead of by significant differences in the derived magnetic field values. By combining our results with past FORS1 measurements of HD46328, we improve the estimate of the stellar rotation period, obtaining P = 2.17950+/-0.00009 days. For HD125823, our FORS2 measurements do not fit the available magnetic field model, based on magnetic field values obtained 30 years ago. We repeatedly detect a magnetic field for the O9.7V star HD54879, the HD164492C massive binary, and the He-rich star CPD -57 3509. We obtain a magnetic field detection rate of 6+/-4%, while by considering only the apparently slow rotators we derive a detection rate of 8+/-5%, both comparable with what was previously reported by other similar surveys. We are left with the intriguing result that, although the large majority of magnetic massive stars is rotating slowly, our detection rate is not a strong function of the stellar rotational velocity.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Fossati, L.
Castro, N.
Schoeller, M.
Hubrig, S.
Langer, N.
Morel, Thierry  ;  Université de Liège > Groupe d'astrophysique des hautes énergies (GAPHE)
Briquet, Maryline ;  Université de Liège - ULiège
Herrero, A.
Przybilla, N.
Sana, H.
Schneider, F. R. N.
de Koter, A.
the BOB collaboration
More authors (3 more) Less
Language :
English
Title :
B fields in OB stars (BOB): low-resolution FORS2 spectropolarimetry of the first sample of 50 massive stars
Publication date :
2015
Journal title :
Astronomy and Astrophysics
ISSN :
0004-6361
eISSN :
1432-0746
Publisher :
EDP Sciences
Volume :
582
Pages :
750
Peer reviewed :
Peer Reviewed verified by ORBi
Commentary :
20 pages, 10 figures, 4 tables; accepted for publication on Astronomy & Astrophysics
Available on ORBi :
since 06 October 2015

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