AAS 207th Meeting, 8-12 January 2006
Session 69 Stellar Evolution
Poster, Tuesday, 9:20am-6:30pm, January 10, 2006, Exhibit Hall

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[69.15] Beryllium: A Cosmic Chronometer?

C. Peruta (University of Arizona & University of Hawaii), A.M. Boesgaard (University of Hawaii)

The process spallation, by which Beryllium is formed, is the key to understanding many topics in astronomy today. It is still not certain whether spallation occurs within the local vicinity of supernovae where C N O is excited into interstellar gas or conversely on a global scale by high energy protons bombarding C N O in the interstellar gas. If global, the instantaneous abundance can be characterized by a scatter around the mean value significantly smaller than for Fe or O. Beryllium would therefore be a more reliable chronometer than [Fe/H] or [O/H]. I present Be abundances from 20 metal poor stars ([Fe/H] < -1.5). The stars were observed with high resolution/high S/N spectroscopy and abundances were determined by fitting synthesized spectra. These abundances are plotted against [Fe/H] and combined with results from previous Be studies to confirm whether or not there is an intrinsic spread in Be at low metallicities. If there is a spread, we can infer the most likely mechanism for Be formation is spallation in the vicinity of supernovae and therefore A(Be) is not a good chronometer. This study shows that there is a spread around [Fe/H] = -1.5 and -2.5 with a typical error of 0.10 dex for all Be abundances. This work was conducted by a Research Experience for Undergraduates (REU) position at the University of Hawaii's Institute for Astronomy and funded by the NSF.

The author(s) of this abstract have provided an email address for comments about the abstract: cperuta@email.arizona.edu

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