High Resolution Study of ^{40}Ca to Constrain Potassium Nucleosynthesis in NGC 2419

Area of Science:

• Nuclear Astrophysics
• Stellar Evolution
• Globular Clusters

Background:

• The Mg-K anticorrelation in globular cluster NGC 2419 is linked to hydrogen burning at 80-260 MK.
• The rate of the potassium-destroying reaction, ^{39}K(p,γ)^{40}Ca, is highly uncertain in this temperature range and critical for models.

Purpose of the Study:

• To significantly constrain the rate of the ^{39}K(p,γ)^{40}Ca reaction.
• To improve the accuracy of nucleosynthesis models for globular clusters.

Main Methods:

• Performed a high-resolution ^{39}K(^{3}He,d)^{40}Ca experiment.
• Resolved the E_{r}^{c.m.}=154 keV resonance in ^{39}K+p for the first time.

Main Results:

• The measured resonance increases the ^{39}K(p,γ)^{40}Ca reaction rate by up to a factor of 13.
• The uncertainty (1σ width) of the reaction rate is reduced by up to a factor of 42.

Conclusions:

• The constrained reaction rate provides a more accurate input for stellar nucleosynthesis calculations.
• This improved rate may lower the required temperatures to reproduce the observed Mg-K anticorrelation in NGC 2419.