Magnetic survey of emission line B-type stars with FORS1 at the VLT

Abstract

We report the results of our search for magnetic fields in a sample of 16 field Be stars, the binary emission-line B-type star upsilon Sgr, and in a sample of fourteen members of the open young cluster NGC3766 in the Carina spiral arm. The sample of cluster members includes Be stars, normal B-type stars and He-strong/He-weak stars. Nine Be stars have been studied with magnetic field time series obtained over ~1 hour to get an insight into the temporal behaviour and the correlation of magnetic field properties with dynamical phenomena taking place in Be star atmospheres. The spectropolarimetric data were obtained at the European Southern Observatory with the multi-mode instrument FORS1 installed at the 8m Kueyen telescope. We detect weak photospheric magnetic fields in four field Be stars, HD62367, mu Cen, o Aqr, and epsilon Tuc. The strongest longitudinal magnetic field, <B_z>=117+-38G, was detected in the Be star HD62367. Among the Be stars studied with time series, one Be star, lambda Eri, displays cyclic variability of the magnetic field with a period of 21.12min. The binary star upsilon Sgr, in the initial rapid phase of mass exchange between the two components with strong emission lines in the visible spectrum, is a magnetic variable star, probably on a timescale of a few months. The maximum longitudinal magnetic field <B_z>=-102+-10G at MJD54333.018 was measured using hydrogen lines. The cluster NGC3766 seems to be extremely interesting, where we find evidence for the presence of a magnetic field in seven early B-type stars out of the observed fourteen cluster members.

arXiv comment9 pages, 8 figures, 3 tables, accepted for publication in Astronomische Nachrichten

References in corpus (10)

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• Detection of Magnetic Massive Stars in the Open Cluster NGC 3766
• Protodiscs around Hot Magnetic Rotator Stars

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• B fields in OB stars (BOB): Concluding the FORS2 observing campaign
• On the consistency of magnetic field measurements of Ap stars: lessons learned from the FORS1 archive
• Are there tangled magnetic fields on HgMn stars?
• Identification of new classical Be stars from the LAMOST MRS survey
• The Circumstellar Disk of the Be Star $o$~Aquarii
• Be Stars: Rapidly Rotating Pulsators
• Detection of anomalous element distribution in the extremely slowly rotating magnetic O9.7 V star HD 54879
• The magnetic field of the stripped primary in the upsilon Sgr system, a member of the rare class of hydrogen-deficient binaries
• Detection of a weak magnetic field in the Balmer emission line white dwarf WDJ1653-1001