Physics
Scientific paper
Jul 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995hst..prop.5859d&link_type=abstract
HST Proposal ID #5859
Physics
Hst Proposal Id #5859 Cool Stars
Scientific paper
A theoretical study of NLTE effects in the analysis of HST boron observations indicates that all currently-reported abundances are wrong by factors of 2.5-4X. (A systematic effect much larger than any measurement error). If true, this would force major changes in the modelling of Be and B abundances as products of cosmic ray spallation plus direct production by supernovae in the early galaxy. It would help explain why no simple model of galactic chemical evolution can yet explain the evolution of the light elements Li, Be, and B at the same time as the evolution of heavier elements such as Fe and O. We can test the NLTE prediction by observing the BII line at 1362 Angstrom in the star Procyon, whose BI abundance has been extremely well determined from two groups previous HST observations of the BI 2500Angstrom line. (The repaired GHRS opens the possibility of observing the BII line). Our calculations (see figures) demonstrate we should easily see if large amounts of B are being "hidden" (from BI observations) by being in the form of BII. We will use the star Sirius as a reference for differential analysis. BII was observed in Vega and Sirius by the Copernicus satellite 20 years ago, and our re-analysis of this data (see figure) shows we have an excellent chance of success in the present proposal.
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