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Session 81 - Planetary Nebulae.
Display session, Wednesday, January 17
North Banquet Hall, Convention Center
We have carried out FOS spectroscopic observations of the C-poor halo PNe M2-29 and DDDM-1 to study their UV spectrum and determine accurate chemical abundances. M2-29 and DDDM-1 are the most deficient in Ar and S of their group. Accurate C and N abundances for these objects will permit us to: a) study the chemical evolution of the ISM in the early epochs of the formation of the Galaxy, b) determine the fraction of C in the interstellar medium at present produced by SNe of Type II and the fraction produced by stars with initial masses < 8 M_ødot (the progenitors of PNe and SNeIa), c) constrain observationally the nuclear reaction rate C(\alpha,\gamma)O by comparing the observed C/O ratio in the primitive halo with the C/O ratio predicted from SNe models, and d) study and constrain the stellar evolution models of low mass stars, those with initial masses in the 0.8 - 1 M_ødot range. During HST Cycle 3 we obtained WFC1 direct imagery in H\alpha of these two very small objects.
Program listing for Wednesday