TY  - JOUR
A1  - Schöller, Markus
A1  - Hubrig, Swetlana
A1  - Fossati, L.
A1  - Carroll, Thorsten Anthony
A1  - Briquet, Maryline
A1  - Oskinova, Lida
A1  - Järvinen, S.
A1  - Ilyin, Ilya
A1  - Castro, N.
A1  - Morel, T.
A1  - Langer, N.
A1  - Przybilla, N.
A1  - Nieva, M. -F.
A1  - Kholtygin, A. F.
A1  - Sana, H.
A1  - Herrero, A.
A1  - Barba, R. H.
A1  - de Koter, A.
T1  - B fields in OB stars (BOB)
BT  - Concluding the FORS2 observing campaign
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Aims. The B fields in OB stars (BOB) Collaboration is based on an ESO Large Programme to study the occurrence rate, properties, and ultimately the origin of magnetic fields in massive stars. Methods. In the framework of this program, we carried out low-resolution spectropolarimetric observations of a large sample of massive stars using FORS2 installed at the ESO VLT 8m telescope. Results. We determined the magnetic field values with two completely independent reduction and analysis pipelines. Our in-depth study of the magnetic field measurements shows that differences between our two pipelines are usually well within 3 sigma errors. From the 32 observations of 28 OB stars, we were able to monitor the magnetic fields in CPD -57 degrees 3509 and HD164492C, confirm the magnetic field in HD54879, and detect a magnetic field in CPD -62 degrees 2124. We obtain a magnetic field detection rate of 6 +/- 3% for the full sample of 69 OB stars observed with FORS 2 within the BOB program. For the preselected objects with a nu sin i below 60 km s(-1), we obtain a magnetic field detection rate of 5 +/- 5%. We also discuss X-ray properties and multiplicity of the objects in our FORS2 sample with respect to the magnetic field detections.
KW  - polarization
KW  - stars: early-type
KW  - stars: magnetic field
KW  - stars: massive
Y1  - 2017
U6  - https://doi.org/10.1051/0004-6361/201628905
SN  - 1432-0746
VL  - 599
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Hubrig, Swetlana
A1  - Schoeller, M.
A1  - Ilyin, Ilya
A1  - Kharchenko, N. V.
A1  - Oskinova, Lida
A1  - Langer, N.
A1  - Gonzalez, J. F.
A1  - Kholtygin, A. F.
A1  - Briquet, Maryline
T1  - Exploring the origin of magnetic fields in massive stars - II. New magnetic field measurements in cluster and field stars
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context. Theories on the origin of magnetic fields in massive stars remain poorly developed, because the properties of their magnetic field as function of stellar parameters could not yet be investigated. Additional observations are of utmost importance to constrain the conditions that are conducive to magnetic fields and to determine first trends about their occurrence rate and field strength distribution.
 Aims. To investigate whether magnetic fields in massive stars are ubiquitous or appear only in stars with a specific spectral classification, certain ages, or in a special environment, we acquired 67 new spectropolarimetric observations for 30 massive stars. Among the observed sample, roughly one third of the stars are probable members of clusters at different ages, whereas the remaining stars are field stars not known to belong to any cluster or association.
 Methods. Spectropolarimetric observations were obtained during four different nights using the low-resolution spectropolarimetric mode of FOcal Reducer low dispersion Spectrograph (FORS 2) mounted on the 8-m Antu telescope of the VLT. Furthermore, we present a number of follow-up observations carried out with the high-resolution spectropolarimeters SOFIN mounted at the Nordic Optical Telescope (NOT) and HARPS mounted at the ESO 3.6 m between 2008 and 2011. To assess the membership in open clusters and associations, we used astrometric catalogues with the highest quality kinematic and photometric data currently available.
 Results. The presence of a magnetic field is confirmed in nine stars previously observed with FORS 1/2: HD36879, HD47839, CPD-28 2561, CPD-47 2963, HD93843, HD148937, HD149757, HD328856, and HD164794. New magnetic field detections at a significance level of at least 3 sigma were achieved in five stars: HD92206c, HD93521, HD93632, CPD-46 8221, and HD157857. Among the stars with a detected magnetic field, five stars belong to open clusters with high membership probability. According to previous kinematic studies, five magnetic O-type stars in our sample are candidate runaway stars.
KW  - polarization
KW  - stars: early-type
KW  - stars: kinematics and dynamics
KW  - stars: magnetic field
KW  - stars: massive
KW  - open clusters and associations: general
Y1  - 2013
U6  - https://doi.org/10.1051/0004-6361/201220721
SN  - 0004-6361
VL  - 551
PB  - EDP Sciences
CY  - Les Ulis
ER  -