The hypothesis that Barium stars are the product of mass transfer across a binary system is reviewed with special attention given to the chemical composition of AGB stars (the mass-losing star in the binary) and the Ba stars (the mass-gaining star).

High S/N spectroscopic studies of the abundance patterns characterizing extremely metal-deficient halo field stars and globular cluster stars have served to provide significant clues to and increasingly stringent boundary conditions upon the chemical evolution of the halo population of our galaxy. Guided by our current knowledge of nucleosynthesis as a function of stellar mass occurring in stars and supernovae, we identify some interesting constraints that these combined observational and theoretical considerations impose upon theories of the early history of our galaxy.

We have obtained spectra near 3130 Å of 23 F and G main-sequence stars at 0.05 Å px−1. We have made preliminary estimates of the equivalent widths for the Be II doublet at 3130.4 and 3131.1 Å by means of a comparison procedure that matches each star against a standard star of similar spectral type with known Be abundance. It appears that stars that are deficient in Be are very uncommon. The halo dwarf, HD 76932, clearly has Be.

We show that the carbon isotope ratio 12C/13C in the atmosphere of dwarf stars can be determined with reasonable accuracy from high resolution, high signal-to-noise ratio observations of the CH G-band in their spectra. Lines suitable for this purpose are selected from consideration of the solar case, for which 12C/13C = 89 is derived. A preliminary analysis of these features in the spectra of μ Her, δ Eri and τ Cet yields 12C/13C values of 84, 80 and 150 respectively.

It is suggested that the position of BaII stars with respect to normal red giants in the (log L, 12C/13C) and ([C/Fe],12C/13C) diagrams supports the hypothesis that 13C(α,n)16O was the neutron source responsible for the synthesis of the heavy elements now present in the BaII star envelopes.

We review briefly the observational status of abundance determinations for those elements produced in the first seconds of a “standard” Big Bang Universe, showing that although [4He] and [D] appear not to be mutually compatible there is still room for reconciliation via astration of D, for values consistent with estimated [7Li]. New limits to production cross-sections for 7Li appear to limit Nv (the number of light neutrino types) to no more than 3. Non-standard models with fluctuations are briefly considered; they are attractive because they use Ω = 1 and may also yield early C, N, O in significant quantities. The true value of 7Li [10-9 or 10−10 w.r.t. H] is the critical test here. We show where spectra of improved S:N are needed to progress in constraining cosmological models.

This contribution starts with a very brief updated report on our present knowledge concerning the primordial abundances of the lightest elements (D, 3He, 4He and 7Li). From this information it is claimed here that specific models of chemical evolution able to account for a thorough destruction of D during the galactic history should be involved to reconcile the ratios : η = ηB/ηγ (baryonic density relative to background photon density) predicted respectively from the primordial 4He (Y) abundance and from the primordial D (and 3He) abundance. Among different possibilities; it is shown that galactic evolution models implying variations of the role of star formation (SFR) are more successful for that goal than models implying bimodal star formation. From this analysis it is also argued that contrary to a common belief, a large D destruction rate over the galactic history implies very specific conditions concerning the chemical evolution of our galaxy.

A summary of the main subjects discussed at this symposium is given, and some suggestions for future high signal-to-noise spectroscopic work, which could have a major impact on our understanding of the physics of stars and on astrophysics in general are presented.

FURENLID Without breaking the orderly progression of events during these last moments of IAU Symposium No. 132, I would like to insert a few words. We have just finished an excellent Symposium, and at this point there is no more any discussion or arguments when we all join in gratitude to the supporting staff at the meeting as well as to the scientific and local organizing committees. The Symposium has for me been like a school, where I have found myself -except for 11 too short minutes- on the appropriate side of the teacher's desk, the student side. The teachers were outstanding! Our special thanks go to the Principal of this school, Dr. Giusa Cayrel, and as a small token of gratitude I would like to present her with a copy of the solar flux atlas. Dr. Cayrel, you are dear to us and we thank you very much!