S stars: infrared colors, technetium, and binarity

Details S stars: infrared colors, technetium, and binarity S stars: infrared colors, technetium, and binarity

Apr 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26a...271..463j&link_type=abstract

Astronomy and Astrophysics, Vol. 271, p. 463 (1993)

Astronomy and Astrophysics

Astrophysics

50

Stars: Late-Type, Giants, Asymptotic Giant Branch, Evolution, Circumstellar Matter, Binaries: Spectroscopic

Scientific paper

S stars without Tc are now widely believed to be "accidental" (or "extrinsic") S stars, cool analogs of barium stars, whose heavy element enrichment is due to earlier mass transfer from a more massive companion, now a white dwarf (WD). A further test of this scenario can be based on infrared colors, which provide a measure of circumstellar dust. Such dust is expected to be present around intrinsic S stars, populating the asymptotic giant branch (AGB) and suffering from a severe mass loss, but not necessarily around extrinsic S stars, which are characterized by photospheric IR colors (no dust emission). Infrared fluxes of S stars were obtained from the IRAS Point Source Catalogue and the Two Micron Sky Survey, and the flux ratios F(12μm)/F(2.2μm) were calculated. Stars showing Tc generally had values ≥ 0.10, whereas Tc-deficient S stars were found to have R < 0.10. The (K - [12], K - [251) color - color diagram can be used in much the same way to distinguish intrinsic from extrinsic S stars. Using these IR criteria, the frequency of intrinsic S stars in Stephenson's General Catalogue is found to be at least 50%. Population characteristics and magnitude distributions also differ, and indicate that intrinsic S stars may belong to a younger and/or brighter population.
The paradigm stating that binary S stars systematically lack Tc is furthermore confirmed from a CORAVEL radial velocity monitoring of an extended sample of S stars. The results presented in this paper further strengthen the hypothesis that Tc-deficient and Tc-rich S stars represent different evolutionary stages. As a corollary, the respective locations of intrinsic and extrinsic S stars in the (K - [12], K - [25]) diagram constrain the dredge-up history along the AGB, since no Tc-deficient S stars are found among dusty (i.e. evolved) AGB stars, meaning that the third dredge-up process is always efficient in S stars with a strong mass loss.

Affiliated with

Also associated with

No associations

Rating

S stars: infrared colors, technetium, and binarity does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with S stars: infrared colors, technetium, and binarity, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and S stars: infrared colors, technetium, and binarity will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1368223