11247(  1) - 03/30/07 11:05  - [  1]

                  HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11247

Version: 1    Check-in Time: 30-Mar-2007 15:05:17       STScI Edit Number: 0

Title
Light Element Nucleosynthesis through Measurements of Interstellar Boron
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Type             Cycle     Parallel Pointing Tolerance
AR               16        <none>
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Investigators
                                                                                     Contact?
    PI: Dr. Steven R. Federman            University of Toledo
   CoI: Dr. David L. Lambert              University of Texas at Austin                 N
   CoI: Dr. Yaron Sheffer                 University of Toledo                          N

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Abstract

With the aim of identifying the sources of light element (Li, Be, B, and F)
synthesis, we propose a survey of interstellar boron. The B II line at 1362 A will
be used to extract the B column density along more than fifty sight lines, many of
which are associated with regions of massive star formation shaped by core-collapse
supernovae (SNe II). HST spectra are the only means for determining the elemental B
abundance for sources outside the solar system. The survey will contain directions
that are both molecule poor and molecule rich, thereby enabling us to examine the
overall level of boron depletion onto grains as a function of gas density. Both the
average density of neutral material along the line of sight and the density inferred
from the fraction of neutral gas in molecular form will be incorporated into the
analysis. We will seek sight lines with B abundances enhanced over the value seen in
regions with the least depletion; such enhancements mainly arise from recent
production of B-11. The boron column density, with the fluorine column density
obtained from archival FUSE spectra of the F I line at 954 A, will give the B/F
abundance ratio. This ratio is a diagnostic of the importance of neutrino-induced
spallation in SNe II in effecting synthesis of B and F, a process for which direct
observational evidence is still lacking.
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