Destruction of 22Na in Novae: Surprising Results from an Absolute Measurement of 22Na(p,\gamma ) Resonance Strengths

Abstract

Hydrodynamic simulations of classical novae on ONe white dwarfs predict substantial production of 22 Na. Observation of 22 Na decay should be correlated with the corresponding nova because the half life of 22 Na is only 2.6 years. The 1275-keV gamma ray from the β decay of 22 Na is, therefore, an excellent diagnostic for the nova phenomenon and a long-sought target of gamma-ray telescopes. Nova simulations determine the maximum 22 Na-detection distance to be < 1 kpc for the INTEGRAL spectrometer SPI, consistent with its non-observation to date. However, model estimates are strongly dependent on the thermonuclear rate of the 22 Na(p, γ) 23 Mg reaction, which destroys 22 Na in novae. The 22 Na(p, γ) 23 Mg rate is expected to

\beta -delayed proton decay of 23Al and nova nucleosynthesis

“…at 0.3 GK the Gamov window is 170-360 keV) and the determined proton decay branching ratio (0.32(6) per 100 451 keV γ rays) can be used in combination with the γ-decay branching ratios [8] and the level life-time [14] to determine the resonance strength ωγ for this resonance. Our result ωγ = 1.4(5) meV agrees to the old value 1.8(7) meV from a direct measurement [3], but disagrees with the recent value of 5.7 +1.6 −0.9 meV [4]. Our value does not make significant change in the reaction rate presented in the compilation [16], but confirms and reduces the uncertainties.…”