Astronomy and Astrophysics – Astronomy
Scientific paper
May 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994mnras.268..213p&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Vol. 268, NO. 1/MAY1, P. 213, 1994
Astronomy and Astrophysics
Astronomy
34
Atomic Processes - Line: Formation - Binaries: Symbiotic - Stars: Evolution
Scientific paper
We present an analysis of the He I λλ5876, 6678, 7065 emission lines for a large sample of symbiotic binary stars. As in earlier studies, we find significant deviations from case B predictions for every system considered. In most cases, the λλ5876, 6678 lines distinguish between S- and D-type symbiotics in that 1( 6678)/1( 5876) >0.50 for S-types and I( λ6678)/I(λ5876) ˜0.25 for D-types. We follow Almog & Netzer and derive predicted intensity ratios for comparison with the observations. Our models indicate densities of ne ˜ 1010 cm-3 for most S-type systems and ne ≲1010 cm-3 for all D-type systems. The He I intensity ratios require large optical depths in the He I λ3889 line, τ3889 ˜100-1000, for most sources; the nebular sizes are then roughly 1 au for S-types and 10 au for D-types. These results agree with previous density and size estimates for symbiotics; thus our He I model provides a useful diagnostic for the physical conditions within dense photoionized nebulae.
Kenyon Scott. J.
Mikolajewska Joanna
Proga Daniel
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