Constraining the $^{30}$P($p,γ)^{31}$S reaction rate in ONe novae via the weak, low-energy, $β$-delayed proton decay of $^{31}$Cl

T. Budner; M. Friedman; C. Wrede; B. A. Brown; J. José; D. Pérez-Loureiro; L. J. Sun; J. Surbrook; Y. Ayyad; D. W. Bardayan; K. Chae; A. A. Chen; K. A. Chipps; M. Cortesi; B. Glassman; M. R. Hall; M. Janasik; J. Liang; P. O'Malley; E. Pollacco; A. Psaltis; J. Stomps; T. Wheeler

Constraining the $^{30}$P($p,γ)^{31}$S reaction rate in ONe novae via the weak, low-energy, $β$-delayed proton decay of $^{31}$Cl

T. Budner, M. Friedman, C. Wrede, B. A. Brown, J. José, D. Pérez-Loureiro, L. J. Sun, J. Surbrook, Y. Ayyad, D. W. Bardayan, K. Chae, A. A. Chen, K. A. Chipps, M. Cortesi, B. Glassman, M. R. Hall, M. Janasik, J. Liang, P. O'Malley, E. Pollacco, A. Psaltis, J. Stomps, T. Wheeler

Abstract

The $^{30}$P$(p,γ)^{31}$S reaction plays an important role in understanding nucleosynthesis of $A\geq 30$ nuclides in oxygen-neon novae. The Gaseous Detector with Germanium Tagging was used to measure $^{31}$Cl $β$-delayed proton decay through the key $J^π=3/2^{+}$, 260-keV resonance. The intensity $I^{260}_{βp} = 8.3^{+1.2}_{-0.9} \times 10^{-6}$ represents the weakest $β$-delayed, charged-particle emission ever measured below 400 keV, resulting in a proton branching ratio of $Γ_p / Γ= 2.5^{+0.4}_{-0.3} \times 10^{-4}$. By combining this measurement with shell-model calculations for $Γ_γ$ and past work on other resonances, the total $^{30}$P$(p,γ)^{31}$S rate has been determined with reduced uncertainty. The new rate has been used in hydrodynamic simulations to model the composition of nova ejecta, leading to a concrete prediction of $^{30}$Si/$^{28}$Si excesses in presolar nova grains and the calibration of nuclear thermometers.

Constraining the $^{30}$P($p,γ)^{31}$S reaction rate in ONe novae via the weak, low-energy, $β$-delayed proton decay of $^{31}$Cl

Abstract

The

S reaction plays an important role in understanding nucleosynthesis of

nuclides in oxygen-neon novae. The Gaseous Detector with Germanium Tagging was used to measure

-delayed proton decay through the key

, 260-keV resonance. The intensity

represents the weakest

-delayed, charged-particle emission ever measured below 400 keV, resulting in a proton branching ratio of

. By combining this measurement with shell-model calculations for

and past work on other resonances, the total

S rate has been determined with reduced uncertainty. The new rate has been used in hydrodynamic simulations to model the composition of nova ejecta, leading to a concrete prediction of

Si/

Si excesses in presolar nova grains and the calibration of nuclear thermometers.

Paper Structure (2 figures)

This paper contains 2 figures.

Figures (2)

Figure 1: [Color online] $^{31}$Cl $\beta$-delayed proton spectrum measured by only the central detector pad [black] and for event-level summing of the five inner detector pads [grey (pink online)] up to 1.5 MeV. The energy spectrum sums the ionization deposited in the P10 gas from both the decay protons and recoiling $^{30}$P nuclei. $\beta^+$ particles are responsible for the large background at low energies and can also sum with ionization produced by proton tracks, leading to a detector response that is skewed to the right; this effect is larger in the combined-pad spectrum due to the effective increase in detection pad area.
Figure 2: [Color online] (a) Contributions of individual resonances to the $^{30}$P$(p,\gamma)^{31}$S reaction rate and the total summed thermonuclear rate [solid black] plotted over peak nova temperatures. (b) The ratio between the experimental resonant reaction rate and the Hauser-Feshbach statistical rate Rauscher2000. The solid curve represents the recommended central rate, while the dashed curves indicate the upper and lower limits on the resonant rate calculation.