Uncertainties in the $^{18}$F(p,$alpha$)$^{15}$O reaction rate in classical novae. (arXiv:2106.02606v2 [nucl-th] UPDATED)
<a href="http://arxiv.org/find/nucl-th/1/au:+Kahl_D/0/1/0/all/0/1">D. Kahl</a>, <a href="http://arxiv.org/find/nucl-th/1/au:+Jose_J/0/1/0/all/0/1">J. José</a>, <a href="http://arxiv.org/find/nucl-th/1/au:+Woods_P/0/1/0/all/0/1">P.J. Woods</a>
Context. Direct observation of gamma-ray emission from the decay of $^{18}$F
ejected in classical nova outbursts remains a major focus of the nuclear
astrophysics community. However, modeling the abundance of ejected $^{18}$F,
and thus the predicted detectability distance of a gamma-ray signal near 511
keV emitted from these transient thermonuclear episodes, is hampered by
significant uncertainties in our knowledge of the key $^{18}$F(p,$alpha$)
reaction rate. Aims. We analyze uncertainties in the most recent nuclear
physics experimental results employed to calculate the $^{18}$F(p,$alpha$)
reaction rate. Our goal is to determine which uncertainties have the most
profound influence on the predicted abundance of $^{18}$F ejected from novae,
in order to guide future experimental works. Methods. We calculated a wide
range of $^{18}$F(p,$alpha$) reaction rates using R-Matrix formalism, allowing
us to take into account all interference effects. Using a selection of 16
evenly-spaced rates over the full range, we performed 16 new hydrodynamic nova
simulations. Results. We performed one of the most thorough theoretical studies
of the impact of the $^{18}$F(p,$alpha$) reaction in classical novae to date.
The $^{18}$F(p,$alpha$) rate remains highly uncertain at nova temperatures,
resulting in a factor ~10 uncertainty in the predicted abundance of $^{18}$F
ejected from nova explosions. We also found that the abundance of $^{18}$F may
be strongly correlated with that of $^{19}$F. Conclusions. Despite numerous
nuclear physics uncertainties affecting the $^{18}$F(p,$alpha$) reaction rate,
which are dominated by unknown interference signs between 1/2$^+$ and 3/2$^+$
resonances, future experimental work should focus on firmly and precisely
determining the directly measurable quantum properties of the subthreshold
states in the compound nucleus $^{19}$Ne near 6.13 and 6.29 MeV.
Context. Direct observation of gamma-ray emission from the decay of $^{18}$F
ejected in classical nova outbursts remains a major focus of the nuclear
astrophysics community. However, modeling the abundance of ejected $^{18}$F,
and thus the predicted detectability distance of a gamma-ray signal near 511
keV emitted from these transient thermonuclear episodes, is hampered by
significant uncertainties in our knowledge of the key $^{18}$F(p,$alpha$)
reaction rate. Aims. We analyze uncertainties in the most recent nuclear
physics experimental results employed to calculate the $^{18}$F(p,$alpha$)
reaction rate. Our goal is to determine which uncertainties have the most
profound influence on the predicted abundance of $^{18}$F ejected from novae,
in order to guide future experimental works. Methods. We calculated a wide
range of $^{18}$F(p,$alpha$) reaction rates using R-Matrix formalism, allowing
us to take into account all interference effects. Using a selection of 16
evenly-spaced rates over the full range, we performed 16 new hydrodynamic nova
simulations. Results. We performed one of the most thorough theoretical studies
of the impact of the $^{18}$F(p,$alpha$) reaction in classical novae to date.
The $^{18}$F(p,$alpha$) rate remains highly uncertain at nova temperatures,
resulting in a factor ~10 uncertainty in the predicted abundance of $^{18}$F
ejected from nova explosions. We also found that the abundance of $^{18}$F may
be strongly correlated with that of $^{19}$F. Conclusions. Despite numerous
nuclear physics uncertainties affecting the $^{18}$F(p,$alpha$) reaction rate,
which are dominated by unknown interference signs between 1/2$^+$ and 3/2$^+$
resonances, future experimental work should focus on firmly and precisely
determining the directly measurable quantum properties of the subthreshold
states in the compound nucleus $^{19}$Ne near 6.13 and 6.29 MeV.
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