How Do Nuclear Isomers Influence the Gamma-Ray Bursts in Binary Neutron Star Mergers?

• Main Authors: Hamilton, Maria C. Babiuc, Powell, Joseph I
• Format: Journal Article
• Language: English
• Published: 03-08-2024
• Subjects: Physics - High Energy Astrophysical Phenomena
• DOI: 10.48550/arxiv.2402.06498

Front. Astron. Space Sci., Sec. Cosmology, Volume 11 (2024) Neutron star mergers are astrophysical `gold mines,' synthesizing over half
of the elements heavier than iron through rapid neutron capture
nucleosynthesis. The observation of the binary neutron star merger GW170817,
detected both in gravitational waves and electromagnetic radiation, marked a
breakthrough. One electromagnetic component of this event, the gamma ray burst
GRB 170817A, has an unresolved aspect: the characteristics of its prompt
gamma-ray emission spectrum. In this work, we investigate how gamma-ray spectra
in such GRBs may be influenced by de-excitations from isomeric transitions. Our
study begins with a review of current knowledge on GRB structure and of
r-process nucleosynthesis in neutron star collisions, focusing on the role of
nuclear isomers in these settings. We then test our hypothesis by developing
criteria to select representative isomers, based on known solar element
abundances, for modeling GRB spectral characteristics. We integrate these
criteria into an interactive web page, facilitating the construction and
analysis of relevant gamma-ray spectra from isomeric transitions. Our analysis
reveals that three isomers (zirconium, lead and yttrium) stand out for their
potential to impact the prompt GRB spectrum due to their specific properties.
This information allows us to incorporate nuclear isomer data into
astrophysical simulations and calculate isomeric abundances generated by
astrophysical r-processes in neutron star mergers and their imprint on the
detected signal.