Experimentally well-constrained masses of $^{27}$P and $^{27}$S: Implications for studies of explosive binary systems
nucl-ex
/ Authors
L. J. Sun, X. X. Xu, S. Q. Hou, C. J. Lin, J. José, J. Lee, J. J. He, Z. H. Li, J. S. Wang, C. X. Yuan
and 51 more authors
F. Herwig, J. Keegans, T. Budner, D. X. Wang, H. Y. Wu, P. F. Liang, Y. Y. Yang, Y. H. Lam, P. Ma, F. F. Duan, Z. H. Gao, Q. Hu, Z. Bai, J. B. Ma, J. G. Wang, F. P. Zhong, C. G. Wu, D. W. Luo, Y. Jiang, Y. Liu, D. S. Hou, R. Li, N. R. Ma, W. H. Ma, G. Z. Shi
/ Abstract
The mass of $^{27}$P was predicted to impact the X-ray burst (XRB) model predictions of burst light curves and the composition of the burst ashes. To address the uncertainties and inconsistencies in the reported $^{27}$P masses in literature, a wealth of information has been extracted from the $β$-decay spectroscopy of the drip-line nucleus $^{27}$S. We determine the most precise mass excess of $^{27}$P to date to be $-659(9)$~keV, which is 63~keV (2.3$σ$) higher than the AME2016 recommended value of $-722(26)$~keV. The experimentally unknown mass excess of $^{27}$S was estimated to be 17030(400)~keV in AME2016, and we constrain this mass to be 17678(77)~keV based on the measured $β$-delayed two-proton energy. In the temperature region of $(0.06-0.3)$~GK, the $^{26}$Si$(p,γ)^{27}$P reaction rate determined in this work is significantly lower than the rate recommended in the reaction rate libraries, up to two orders of magnitude around 0.1~GK. The impact of these newly determined masses and well-constrained rate on the modeling of the explosive astrophysical scenarios has been explored by hydrodynamic nova and post-processing XRB models. No substantial change was found in the nova contribution to the synthesis of galactic $^{26}$Al or in the XRB energy generation rate, but we found that the calculated abundances of $^{26}$Al and $^{26}$Si at the last stage of XRB are increased by a factor of 2.4. We also conclude that $^{27}$S is not a significant waiting point in the rapid proton capture process.