1999A&A...345..127V -
Astronomy and Astrophysics, volume 345, 127-136 (1999/5-1)
The Henize sample of S stars. I. The technetium dichotomy.
VAN ECK S. and JORISSEN A.
Abstract (from CDS):
This paper is the first one in a series investigating the properties of the S stars belonging to the Henize sample (205 S stars with δ←25° and R<10.5) in order to derive the respective properties (like galactic distribution and relative frequencies) of intrinsic (i.e. genuine asymptotic giant branch) S stars and extrinsic (i.e. post mass-transfer binary) S stars. High-resolution (R=30000 to 60000) spectra covering the range λλ4230-4270Å have been obtained for 76 S stars, 8 M stars and 2 symbiotic stars. The λ4262Å and λ4238Å blends involving a TcI line were analysed separately and yield consistent conclusions regarding the presence or absence of technetium. Only one `transition' case (Hen 140 = HD 120179, a star where only weak lines of technetium are detectable) is found in our sample. A resolution greater than R=30000 is clearly required in order to derive unambiguous conclusions concerning the presence or absence of technetium. The Tc/no Tc dichotomy will be correlated with radial velocity and photometric data in a forthcoming paper.
Abstract Copyright:
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Journal keyword(s):
stars: abundances - stars: binaries: symbiotic - stars: evolution - stars: AGB and post-AGB
Simbad objects:
16
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