The Evolution of Boron : Implications for Galactic Evolution and Cosmology: Cycle 4 Carryover

Details The Evolution of Boron : Implications for Galactic Evolution and Cosmology: Cycle 4 Carryover The Evolution of Boron : Implications for Galactic Evolution and Cosmology: Cycle 4 Carryover

Jul 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994hst..prop.5693d&link_type=abstract

HST Proposal ID #5693

Physics

Hst Proposal Id #5693 Cool Stars Evolution/Cosmology

Scientific paper

We propose to observe boron in late type stars of metallicities ranging from disk to extreme halo and combine this data with our ground-based measurements of Be and Li. The evolution of Li, Be, and B has now been shown to be a powerful descriminant between different models of the chemical and dynamical evolution of the galaxy, and must be added to the evolution of [Fe/H] and [O/H] as the critical test of such models. Light element production depends on the intensity and shape of the cosmic ray spectrum, which in turn depends on the supernova rate and thus the star formation rate. It also depends on the rise of the (progenitor) CNO abundances, and the decline of the gas mass fraction, which is affected by rates of infall of fresh (unprocessed) material and outflow, e.g. by supernova heating. By concentrating on stars at the transition from old disk to halo and in the halo population we can learn the most about the importance of each of these critcal properties of the early galaxy. Already the first 3 HST observations of B in halo stars CANNOT be matched by existing models of galactic chemical evolution (4). -- In addition, the search for primordial B and Be in the most metal-poor stars is the key for discriminating between standard and inhomogeneous big bang nucleosynthesis models. Some recent evidence hints at inconsistancy in the standard model, and accurate observations of B and Be are critical to test and constrain the various inhomogeneous models.

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