Evidence for weak magnetic fields in early-type emission stars

Abstract

We report the results of our study of magnetic fields in a sample of 15 Be stars using spectropolarimetric data 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 stars, HD56014, HD148184, HD155806, and HD181615. We note that for HD181615 the evolutionary status is not obvious due to the fact that it is a binary system currently observed in the initial rapid phase of mass exchange between the two components. Further, we notify the possible presence of distinct circular polarisation features in the circumstellar components of Ca II H&K in three stars, HD58011, HD117357, and HD181615, hinting at a probable presence of magnetic fields in the circumstellar mass loss disks of these stars. We emphasize the need for future spectropolarimetric observations of Be stars with detected magnetic fields to study the temporal evolution of their magnetic fields and the correlation of magnetic field properties with dynamical phenomena taking place in the gaseous circumstellar disks of these stars.

4 pages, 3 figures, 1 table, accepted for publication in AN

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• A compact pulsar wind nebula model of the gamma-ray loud binary LS I +61 303
• B stars seen at high resolution by XMM-Newton
• Be Stars: Rapidly Rotating Pulsators
• Hot and cool: two emission-line stars with constrasting behaviours in the same XMM-Newton field
• Magnetic fields in massive stars
• The magnetic field of the stripped primary in the upsilon Sgr system, a member of the rare class of hydrogen-deficient binaries