Speaker
Wanpeng Tan
(University of Notre Dame)
Description
15O(alpha,gamma) is one of the main breakout reactions from the hot CNO cycles, which
triggers the thermonuclear runaways or X-ray bursts occurring in accreting neutron
stars. A recent study has shown that this reaction is critical for the burst
amplitude and periodicity of X-ray bursters. However, a direct measurement of this
reaction rate at astrophysically relevant temperatures is not feasible yet due to the
lack of very high intensity radioactive 15O beams. There has been considerable effort
in the past to investigate this reaction rate indirectly by obtaining gamma and alpha
decay widths of the alpha-unbound states in 19Ne. While this approach has been
successful for investigating higher energy resonances, the critical level at 4.03 MeV
remains unknown. This leaves the reaction rate largely uncertain since previous
attempts have only provided limits on its gamma width and its alpha decay branching
ratio. In this talk we present new experimental work conducted at the University of
Notre Dame. Lifetimes of the 4.03 MeV state and other relevant states in 19Ne have
been measured successfully using the 17O(3He,n-gamma) reaction. We will also present
the results of our recent measurement of the alpha-decay branching ratios.
Alpha-unbound states in 19Ne were populated via the reaction 19F(3He,3H-alpha) and
triton-alpha coincidences were observed using a low energy particle detection Silicon
array and the TWINSOL facility. The experimental results and the astrophysical
implications will be discussed in the presentation.
Author
Wanpeng Tan
(University of Notre Dame)
Co-authors
Aaron Couture
(University of Notre Dame)
Annalia Palumbo
(University of Notre Dame)
Claudio Ugalde
(University of Notre Dame)
Edward Stech
(University of Notre Dame)
Elizabeth Strandberg
(University of Notre Dame)
HyeYoung Lee
(University of Notre Dame)
Jason Daly
(University of Notre Dame)
Joachim Görres
(University of Notre Dame)
Manoel Couder
(University of Notre Dame)
Mary Beard
(University of Notre Dame)
Michael Wiescher
(University of Notre Dame)
Paul LeBlanc
(University of Notre Dame)
Sacha Falahat
(University of Notre Dame)
Shawn O’Brien
(University of Notre Dame)
