Recently, significant progress was made in understanding the impact of new masses of ²⁷P and ²⁷S on the X-ray bursts by an international nuclear astrophysical team. 

This work was led by XU Xinxing (China Institute of Atomic Energy & The University of Hong Kong & Institute of Modern Physics, Chinese Academy of Sciences) and HOU Suqing (Institute of Modern Physics, Chinese Academy of Sciences). The results have been published in Physics Letters B.  

Type I X-ray bursts are the most frequent types of thermonuclear stellar explosions in the Galaxy. As one of the key nucleosynthesis processes in X-ray bursts, the rapid proton capture process (rp-process) has always been the important scientific frontiers in nuclear astrophysics since 1975. Nuclear masses are key nuclear physics inputs in rp-process, and the accuracy is vital for soundly understanding the mechanism of X-ray bursts.  

Scientists from the Nuclear Reaction Group of China Institute of Atomic Energy (CIAE), the outstanding user of Heavy Ion Research Facility in Lanzhou, carried out the experiment on measuring the precise mass of ²⁷P based on the Radioactive Ion Beam Line in Lanzhou (RIBLL). The new mass excess of ²⁷P and ²⁷S were determined to be -659(9)keV and 17678(77) keV, respectively. The new ²⁷P mass determined with the highest precision to date, is 63 keV higher than the value recommended in the 2016 atomic mass evaluation. 

Scientists from the Center of Nuclear Physics of the Institute of Modern Physics investigated the impact of the new nuclear masses of ²⁷P and ²⁷S obtained from CIAE on rp-process by collaborating with international nuclear astrophysicists. It is found that the abundance of ²⁶Al in the burst ashes is increased by a factor of 2.4, and ²⁷S is no longer a significant waiting point in rp-process in comparison to the calculations based on the old masses. 

This work was jointly supported by funding agencies such as Major State Basic Research Development Programs of China, National Natural Science Foundation of China, the Youth Innovation Promotion Association of Chinese Academy of Sciences, and the China Postdoctoral Science Foundation.  

Link to the paper : https://doi.org/10.1016/j.physletb.2020.135213