Speaker
Description
Classical nova explosions contribute to the chemical enrichment of the inter-
stellar medium and are potential sources of presolar grains found in primitive
meteorites. The silicon isotopic ratios 29Si/28Si and 30Si/28Si provide im-
portant signatures for identifying the stellar origin of these grains [1, 2].
However, uncertainties in nuclear reaction rates limit our ability to establish
the nova paternity of these grains. In particular, the 29Si(p,γ)30P reaction
influences silicon isotopic abundances and the production of 30P [3, 4].
While considerable progress has been made in determining the strengths of
astrophysically important resonances [5, 6], the nonresonant contribution
to the 29Si(p,γ)30P cross section has not been experimentally investigated
before. We measured this contribution for the first time at four proton
energies between 1.0 and 1.43 MeV, using the activation technique.
The nonresonant astrophysical S-factors calculated from the measured cross
sections are a factor of 4.3 ± 0.6 higher than previous theoretical direct-
capture component predictions [5]. Although the nonresonant contribution
becomes dominant only at temperatures below approximately 30 MK, this
discrepancy may indicate a limitation in the existing theoretical descrip-
tion. Our results provide new experimental constraints for calculating the
29Si(p,γ)30P reaction rate and motivate further investigations of nonresonant
proton capture in this mass region. Ultimately, improved nuclear reaction
rates will help refine predictions of silicon isotopic abundances and their
interpretation in presolar grains.
REFERENCES
[1] J. José et al., Astrophys. J. 612, 414 (2004).
[2] L. N. Downen et al., Astrophys. J. 928, 128 (2022).
[3] C. Iliadis et al., Astrophys. J. Suppl. Ser. 142, 105 (2002).
[4] J. José et al., Astrophys. J. 560, 897 (2001).
[5] L. N. Downen et al., Phys. Rev. C 105, 055804 (2022).
[6] Zs. Mátyus et al., Eur. Phys. J. A 60, 218 (2024).