IAU Symposium Abstract S186-015P
Are the Bulge carbon stars related to the Sagittarius
Padova Astronomical Observatory, Italy (email@example.com)
If the Sagittarius dwarf galaxy (SDG) is crossing the Galactic disc
once per Gyr (Ibata et al., 1997, AJ 113, 635) a star formation burst
could be the signature of each passage. Carbon stars are due to
their brightness ideal tracers for such a burst.
Ng & Schultheis (1997, A&AS in press) suggested that the bulge
carbon stars from Azzopardi et al. (1991, A&AS 88, 265) might be
located in the SDG. This possibility is analyzed
together with the (candidate) carbon stars found in
the SDG (Whitelock et al., 1996, New Astronomy 1, 57). It might
shed some light on the star formation history of the SDG in the
last 4 Gyr.
The results indicate that the carbon stars are not metal-rich
as previously thought. They have a metallicity comparable to the LMC
with an age between 0.1-1 Gyr. A significant fraction of the carbon
stars have a luminosity fainter than the lower LMC and SMC limit of
respectively Mbol ~ -3.5 and Mbol ~ -3.0.
At present, the TP-AGB models cannot explain this, even if carbon stars
form immediately after they enter the TP-AGB phase.
Mass transfer through binary evolution is suggested as a possible
scenario to explain the origin of these low luminosity carbon stars.