Using astrophysical observables to probe r-process nucleosynthesis

Dr. Xilu Wang
University of Notre Dame

After the multi-messenger observations of the gravitational event GW170817, neutron star mergers (NSMs) are the first verified sites for the rapid neutron capture process (r process), which is responsible for synthesizing about half of the elements heavier than iron observed in our solar system. The optical and infrared observations of that event indicated lanthanide production. However, there is still no direct evidence for the synthesis of the heaviest elements such as gold, platinum, and actinides from NSMs. Additionally, the abundance patterns from NSM r-process nucleosynthesis calculations are not always a good match to the solar data.

Here we will discuss work on probing the r-process nucleosynthesis from NSMs using the astrophysical observables of prompt electromagnetic emissions and abundance yields. First, we will describe a possible NSM electromagnetic signal due to the MeV gamma rays produced from the decays of the r-process species. Such a signal holds the promise to be a distinct signature of the production of heavy fissioning species. We will also summarize works on r-process abundance yields, where the spallation effects on the NSM r-process abundance shapes have been investigated. Lastly, we will show work on the calculation of the abundances of the live r-process radioisotopes produced from near-earth supernovae and neutron star mergers and the use of AMS measurements of interesting isotopes, like Fe60, Pu244, etc., to constrain the possible near-earth r-process event.

In the next several years, more NSMs are expected to be detected from the gravitational-wave observatories like LIGO. The potential follow-up multi-messenger observations of new NSM events, together with more stellar observations of metal-poor stars, and the improved nuclear data for r-process isotopes with upcoming nuclear experiments like FRIB, as well as new AMS measurements of the r-process radioisotopes on the earth and moon, would provide a wealth of information for r-process studies. In this exciting era, we are looking forward to using astrophysical observables to seek the answers to the origin of the heaviest elements in our universe.

Hosted by Prof. Surman

All interested persons are invited to attend remotely—email nsladmin@nd.edu for information.