Colloquium on Jun. 10, 2025

Multi-messenger Signatures of Explosive Nucleosynthesis from Neutron Stars Binaries

Speaker: Nobuya Nishimura (University of Tokyo)

Venue: SWIFAR Building 2111

Time: 16:00 PM, Tuesday, Jun. 10, 2025

Abstract:

Binary neutron stars, which are systems containing at least one neutron star, exhibit intense phenomena that differ from those seen in the evolution of isolated neutron stars due to interactions with their companions. These systems may undergo catastrophic merger events after long-term evolution, while neutron stars with low-mass companions can experience surface explosions triggered by mass accretion. Such explosive astronomical phenomena produce multi-messenger signals, including electromagnetic radiation across multiple wavelengths and gravitational waves. In particular, explosive nuclear burning and nucleosynthesis processes play a key role in powering optical transients and are closely related to the cosmic origin of the elements. In this talk, I will provide an overview of explosive nucleosynthesis via the r-process in neutron star mergers and the rp-process in X-ray bursts. Regarding neutron star mergers, I will report recent progress in our understanding of the r-process in the aftermath of the gravitational wave event GW170817, particularly focusing on its implications for the chemical evolution of galaxies. For X-ray bursts, I will discuss recent observations of the peculiar clocked burster SRGA J144459.2–604207, and show how these observations can constrain not only the equation of state of the neutron star but also the nature of its companion star. While the main focus will be on astronomical aspects, I will also highlight the nuclear physics implications and address relevant legacy issues where appropriate.