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The Variable Ca II Absorption in β Pictoris during 1998

Published online by Cambridge University Press:  05 March 2013

S. I. Barnes ,
William Tobin  and
K. R. Pollard
S. I. Barnes
Affiliation:
Mount John University Observatory & Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand; s.barnes@phys.canterbury.ac.nz
William Tobin
Affiliation:
Mount John University Observatory & Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand; w.tobin@phys.canterbury.ac.nz
K. R. Pollard
Affiliation:
Mount John University Observatory & Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand; k.pollard@phys.canterbury.ac.nz
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Abstract

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Variable absorption features were observed in the visible and ultraviolet spectrum of β Pictoris soon after this star gained attention in the early 1980s due to its large IRAS infrared excess and the discovery, from optical imaging, of an edge-on dust disk. The absorption has been attributed to the evaporation of infalling planetesimals or comet-like bodies (the falling evaporating bodies, or FEB, hypothesis). With a view to confronting this hypothesis with fuller observations, we monitored the Ca II H and K lines in β Pictoris simultaneously during 1998, obtaining sequences of spectra on 50 nights. Variable absorption was usually present. The different oscillator strengths of the H and K lines permit the determination of covering factors, but detailed modelling is required to test whether all features can be explained by the FEB hypothesis. The blend of Ca II H with Balmer H ε means that the H and K photospheric profiles are different, and that the variable absorption features do not evolve in parallel. The behaviour of the variable absorption on November 27 is evocative of a body passing in front of the stellar disk in a prograde equatorial orbit.

Keywords

circumstellar matterline: profilesstars: individual (β Pictoris)
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Volume 17 , Issue 3 , 2000 , pp. 241 - 243
Copyright
Copyright © Astronomical Society of Australia 2000

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