Evidence for wind and accretion in the Herbig Be star HD 100546 from FUSE observations

¹ Laboratoire d'Astrophysique de Marseille, BP 8, 13376 Marseille Cedex 12, France
² Université de Provence – CMI, 39 rue J. Curie, 13453 Marseille Cedex 13, France
³ Institut d'Astrophysique de Paris, 98bis bd Arago, 75014 Paris, France
⁴ Dept. of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Rd., Washington, DC 20015-1305, USA
⁵ Dept. of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218, USA

Corresponding author: M. Deleuil, magali.deleuil@oamp.fr

Received: 30 October 2003
Accepted: 27 December 2003

Abstract

We present the first far-UV spectra of the Herbig Be star HD 100546, observed by the Far Ultraviolet Spectroscopic Explorer (FUSE) as part of the Circumstellar Disks team program. We identified and analyzed numerous narrow absorption lines of circumstellar origin. Intense, broad and fairly asymmetric emission lines of , , and were also detected, spanning temperatures up to K. Comparison of the spectra recorded two years apart reveals strong spectral variations, not only in the emission lines but also in the circumstellar lines of , , , and . The varying absorption lines of and exhibit the largest velocity width, from -200 to +320 km s^-1, relative to the star's rest-frame. Variations on a timescale of an hour occurred only in the resonance triplet and (¹D) lines. The spectroscopic variability highlighted by these two observations and the line profile analysis reveal signatures of both outflow and infall processes, which appear to be related in this system. We suggest that these spectral signatures originate in a stellar magnetosphere, which likely interacts with the innermost part of the star's circumstellar disk. This interpretation can account for the main features observed in the spectrum of HD 100546: variable emission and absorption lines as well as suspected continuum variation.