TY - JOUR A1 - Hubrig, Swetlana A1 - Fossati, Luca A1 - Carroll, Thorsten Anthony A1 - Castro, Norberto A1 - Gonzalez, J. F. A1 - Ilyin, Ilya A1 - Przybilla, Norbert A1 - Schoeller, M. A1 - Oskinova, Lida A1 - Morel, T. A1 - Langer, N. A1 - Scholz, Ralf-Dieter A1 - Kharchenko, N. V. A1 - Nieva, M. -F. T1 - B fields in OB stars (BOB): The discovery of a magnetic field in a multiple system in the Trifid nebula, one of the youngest star forming regions JF - Astronomy and astrophysics : an international weekly journal N2 - Aims. Recent magnetic field surveys in O- and B-type stars revealed that about 10% of the core-hydrogen-burning massive stars host large-scale magnetic fields. The physical origin of these fields is highly debated. To identify and model the physical processes responsible for the generation of magnetic fields in massive stars, it is important to establish whether magnetic massive stars are found in very young star-forming regions or whether they are formed in close interacting binary systems. Methods. In the framework of our ESO Large Program, we carried out low-resolution spectropolarimetric observations with FORS 2 in 2013 April of the three most massive central stars in the Trifid nebula, HD 164492A, HD 164492C, and HD 164492D. These observations indicated a strong longitudinal magnetic field of about 500-600 G in the poorly studied component HD 164492C. To confirm this detection, we used HARPS in spectropolarimetric mode on two consecutive nights in 2013 June. Results. Our HARPS observations confirmed the longitudinal magnetic field in HD 164492C. Furthermore, the HARPS observations revealed that HD 164492C cannot be considered as a single star as it possesses one or two companions. The spectral appearance indicates that the primary is most likely of spectral type B1-B1.5 V. Since in both observing nights most spectral lines appear blended, it is currently unclear which components are magnetic. Long-term monitoring using high-resolution spectropolarimetry is necessary to separate the contribution of each component to the magnetic signal. Given the location of the system HD 164492C in one of the youngest star formation regions, this system can be considered as a Rosetta Stone for our understanding of the origin of magnetic fields in massive stars. KW - binaries: close KW - stars: early-type KW - stars: fundamental parameters KW - stars: magnetic field KW - stars: variables: general KW - stars: individual: HD 164492C Y1 - 2014 U6 - https://doi.org/10.1051/0004-6361/201423490 SN - 0004-6361 SN - 1432-0746 VL - 564 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Hubrig, Swetlana A1 - Kholtygin, A. A1 - Ilyin, Ilya A1 - Schöller, M. A1 - Oskinova, Lida T1 - THE FIRST SPECTROPOLARIMETRIC MONITORING OF THE PECULIAR O4 Ief SUPERGIANT zeta PUPPIS JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - The origin of the magnetic field in massive O-type stars is still under debate. To model the physical processes responsible for the generation of O star magnetic fields, it is important to understand whether correlations between the presence of a magnetic field and stellar evolutionary state, rotation velocity, kinematical status, and surface composition can be identified. The O4 Ief supergiant zeta Pup is a fast rotator and a runaway star, which may be a product of a past binary interaction, possibly having had an encounter with the cluster Trumper 10 some 2 Myr ago. The currently available observational material suggests that certain observed phenomena in this star may be related to the presence of a magnetic field. We acquired spectropolarimetric observations of zeta Pup with FORS 2 mounted on the 8 m Antu telescope of the Very Large Telescope to investigate if a magnetic field is indeed present in this star. We show that many spectral lines are highly variable and probably vary with the recently detected period of 1.78 day. No magnetic field is detected in zeta Pup, as no magnetic field measurement has a significance level higher than 2.4 sigma. Still, we studied the probability of a single sinusoidal explaining the variation of the longitudinal magnetic field measurements. KW - stars: atmospheres KW - stars: early-type KW - stars: individual (zetaPup) KW - stars: magnetic field KW - stars: variables: general Y1 - 2016 U6 - https://doi.org/10.3847/0004-637X/822/2/104 SN - 0004-637X SN - 1538-4357 VL - 822 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Hubrig, Swetlana A1 - Oskinova, Lida A1 - Schoeller, M. T1 - First detection of a magnetic field in the fast rotating runaway Oe star zeta Ophiuchi JF - Astronomische Nachrichten = Astronomical notes N2 - The star zeta Ophiuchi is one of the brightest massive stars in the northern hemisphere and was intensively studied in various wavelength domains. The currently available observational material suggests that certain observed phenomena are related to the presence of a magnetic field. We acquired spectropolarimetric observations of zeta Oph with FORS 1 mounted on the 8-m Kueyen telescope of the VLT to investigate if a magnetic field is indeed present in this star. Using all available absorption lines, we detect a mean longitudinal magnetic field < B(z)>(all) = 141 +/- 45 G, confirming the magnetic nature of this star. We review the X-ray properties of zeta Oph with the aim to understand whether the X-ray emission of zeta Oph is dominated by magnetic or by wind instability processes. KW - stars: mass-loss KW - stars: early-type KW - stars: magnetic field KW - stars: kinematics and dynamics KW - X-rays: stars KW - stars: individual: zeta Ophiuchi Y1 - 2011 U6 - https://doi.org/10.1002/asna.201111516 SN - 0004-6337 VL - 332 IS - 2 SP - 147 EP - 152 PB - Wiley-Blackwell CY - Malden 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 - TY - JOUR A1 - Hubrig, Swetlana A1 - Schoeller, Markus A1 - Fossati, Luca A1 - Morel, Thierry A1 - Castro, Neves A1 - Oskinova, Lida A1 - Przybilla, Norbert A1 - Eikenberry, Stephen S. A1 - Nieva, Maria Fernanda A1 - Langer, Norbert T1 - B fields in OB stars (BOB): FORS2 spectropolarimetric follow-up of the two rare rigidly rotating magnetosphere stars HD 23478 and HD 345439 JF - Astronomy and astrophysics : an international weekly journal N2 - Aims. Massive B-type stars with strong magnetic fields and fast rotation are very rare and pose a mystery for theories of star formation and magnetic field evolution. Only two such stars, called sigma Ori E analogues, were known until recently. A team involved in APOGEE, one of the Sloan Digital Sky Survey III programs, announced the discovery of two additional rigidly rotating magnetosphere stars, HD 23478 and HD 345439. The magnetic fields in these newly discovered sOri E analogues have not been investigated so far. Methods. In the framework of our ESO Large Programme and one normal ESO programme, we carried out low-resolution FORS 2 spectropolarimetric observations of HD 23478 and HD 345439. Results. In the measurements of hydrogen lines, we discover a rather strong longitudinal magnetic field of up to 1.5 kG in HD 23478 and up to 1.3 kG using the entire spectrum. The analysis of HD 345439 using four subsequent spectropolarimetric subexposures does not reveal a magnetic field at a significance level of 3 sigma. On the other hand, individual subexposures indicate that HD 345439 may host a strong magnetic field that rapidly varies over 88 min. The fast rotation of HD 345439 is also indicated by the behaviour of several metallic and He I lines in the low-resolution FORS 2 spectra that show profile variations already on this short time-scale. KW - stars: early-type KW - stars: fundamental parameters KW - stars: variables: general KW - stars: magnetic field KW - stars: individual: HD 23478 KW - stars: individual: HD 345439 Y1 - 2015 U6 - https://doi.org/10.1051/0004-6361/201526262 SN - 0004-6361 SN - 1432-0746 VL - 578 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Schoeller, M. A1 - Hubrig, Swetlana A1 - Ilyin, Ilya A1 - Kharchenko, N. V. A1 - Briquet, Maryline A1 - Gonzalez, J. F. A1 - Langer, Norbert A1 - Oskinova, Lida T1 - Magnetic field studies of massive main sequence stars JF - Astronomische Nachrichten = Astronomical notes N2 - We report on the status of our spectropolarimetric observations of massive stars. During the last years, we have discovered magnetic fields in many objects of the upper main sequence, including Be stars, beta Cephei and Slowly Pulsating B stars, and a dozen O stars. Since the effects of those magnetic fields have been found to be substantial by recent models, we are looking into their impact on stellar rotation, pulsation, stellar winds, and chemical abundances. Accurate studies of the age, environment, and kinematic characteristics of the magnetic stars are also promising to give us new insight into the origin of the magnetic fields. Furthermore, longer time series of magnetic field measurements allow us to observe the temporal variability of the magnetic field and to deduce the stellar rotation period and the magnetic field geometry. Studies of the magnetic field in massive stars are indispensable to understand the conditions controlling the presence of those fields and their implications on the stellar physical parameters and evolution. KW - stars: early-type KW - stars: magnetic fields KW - stars: kinematics KW - techniques: polarimetric Y1 - 2011 U6 - https://doi.org/10.1002/asna.201111606 SN - 0004-6337 VL - 332 IS - 9-10 SP - 994 EP - 997 PB - Wiley-Blackwell CY - Malden ER - 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 -