Pictoris during 1998
S.I. Barnes, William Tobin, K.R. Pollard
, PASA, 17 (3), 241.
Next Section: Introduction
The Variable CaII Absorption in
Pictoris during 1998
S.I. Barnes - William Tobin - K.R. Pollard
Mount John University Observatory & Department of Physics and Astronomy,University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand
s.barnes, w.tobin, k.pollard@phys.canterbury.ac.nz
Abstract:
Variable absorption features were observed in the visible and ultraviolet spectrum of 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 disc. 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 CaII H & K lines in Pictoris simultaneously during 1998, obtaining sequences of spectra on 50 nights. Variable absorption was usually present. The different oscillator strengths of the H & 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 CaIIб H with Balmer H means that the H & 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 disc in a prograde equatorial orbit.
Keywords: circumstellar matter -- line: profiles -- stars: individual ( Pictoris)
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