Research output: Contribution to journal › Comment/debate
Accepted author manuscript, 243 KB, PDFdocument
Original language  English 

Article number  L40 
Journal  Astrophysical Journal Letters 
Journal publication date  12 Sep 2018 
Volume  864 
Issue  2 
DOIs 

Publication status  Published  12 Sep 2018 
Externally published  Yes 
The final rate uncertainty factors presented in the original Letter have been calculated using an inappropriate value for the groundstate contribution in some cases. Revised rate uncertainty factors are presented here. Furthermore, the full version of Equation (6), incomplete in the original Letter, is given. Revised lowenergy neutron capture rates were given in Rauscher (2012a), based on the identification of the groundstate contribution to stellar reaction rates. While the revised rates remain as given in Rauscher (2012a), the assigned uncertainties were incorrectly calculated in some cases. In the calculation of the uncertainty factors U_{new}∗ using Equation (11) in Rauscher (2012a) the laboratory contributions X_{ilab}before the rate revision was used. Instead, the X'_{ilab}of the new rate after revision have to be used. As an alternative to using Equation (11) in Rauscher (2012a) with the new X'_{ilab}it is also possible to still use the previous X_{ilab}but changing Equation (11) in Rauscher (2012a) to formula presented. (1) where r∗ is the (theoretical) stellar rate with uncertainty factor U_{th}, r_{exp} ^{ilab} is the (measured) laboratory rate with uncertainty U_{exp}, and X_{ilab}is the (calculated) laboratory contribution to the stellar rate r∗ as obtained before inclusion of any new information. Above Equation (1) reduces to Equation (11) of Rauscher (2012a) when the actual rate value did not change after inclusion of a new laboratory rate, e.g., when r_{exp} ^{ilab}= r_{th} ^{ilab}. Therefore, the old Equation (11) of Rauscher (2012a) can still be used when only the uncertainties but not the absolute values of the rate changed. Table 1 gives the corrected values for the uncertainties U_{new}∗. They supersede the values given in Table 1 of Rauscher (2012a). Figure 1 provides an updated version of Figure 1 in Rauscher (2012a). It becomes apparent that the overall picture has not changed, with most uncertainty factors being larger than the experimental uncertainties due to the contribution of thermally excited states. As before, the largest uncertainties with U_{new}∗ 1≳ .8 stem from the semiempirical values given in KADoNiS (2009), which are based on theory. In comparison to the previously given uncertainties, most uncertainty reductions are found in the region around mass numbers 150 ≲ A ≲ 190 but they still remain larger than the experimental errors. Finally, it has to be noted that Equation (6) in Rauscher (2012a) is incomplete. The full expression for the effective cross section reads (Holmes et al. 1976; Rauscher 2011, 2012b) Formula Presented. (2) with J_{0}, J_{i} being the spins of the target ground state and target excited state i, and σ^{i  j} (E E_{i}) being the partial cross section at energy E  E_{i} from target level i with excitation energy E_{i} to final level j (following Fowler 1974, partial cross sections at zero or negative energies are set to zero). Thanks go to Claudia LedererWoods for pointing out the need for amendment of the rate uncertainties as given in Table 1 of Rauscher (2012a).
ID: 15645418