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Colloquium
Nuclear
Fireworks in Stars via the Breakout
from the CNO Cycle
Dr. Wanpeng Tan
University of Notre Dame
Wednesday,
April 19, 2006 4:00 p.m. NSH 118
(Refreshments at
3:30 p.m. NSH 284)
Close binary stars are the superior astrophysical laboratories
for studying the laws of physics under extreme conditions. Explosive
fireworks in mass-accreting white dwarfs and neutron stars of
binary systems have been observed as novae, supernovae Ia, and
X-ray bursts, respectively. Studies have shown that the hot CNO
cycles and the ensuing thermonuclear processes after the breakout
play a principal role in energy production and nucleosynthesis
in these explosive environments. In particular, the 15O(a,g)
breakout reaction is critical for the explanation of the burst
amplitude and periodicity of X-ray bursters. However, its reaction
rate remains largely uncertain although there has been considerable
effort in the past twenty years to investigate this reaction rate
indirectly due to the lack of high intensity radioactive 15O beams
for direct measurement. New experimental work conducted at the
University of Notre Dame will be presented. Our experimental results
on this reaction rate and the corresponding astrophysical implications
will be discussed in the talk.
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