Welcome to the International Molecule-type Workshop "Nucleosynthesis and electromagnetic counterparts of neutron-star mergers: Preparation for the new discovery", May 11-30 2019, at Yukawa Institute for Theoretical Physics, Kyoto, Japan

In August 2017, the binary neutron star merger was for the first time observed by gravitational-wave detectors and a number of electromagnetic telescopes (GW170817). In particular, from the observations by the X-ray, ultraviolet, optical, infrared, and radio telescopes, a wide variety of information for the processes of the merger and post-merger was obtained. The observational results in the ultraviolet, optical, and infrared bands are in good agreement with the so-called kilonova (macronova) scenario: They indicate that after the merger of binary neutron stars, a neutron-rich matter with mass ~0.03-0.05 solar mass is ejected and r-process nucleosynthesis proceeds in the ejecta, which subsequently shines as an electromagnetic counterpart of the binary neutron star merger. The observational results in the X-ray, optical, and radio bands also suggest that after the merger, a ultra-relativistic jet would be launched, and if we observed this event along the axis of the binary orbital angular momentum, a gamma-ray burst might be observed

Although rich information of the neutron-star merger was obtained in GW170817, we have observed yet only one event. There are still many questions for the neutron-star merger as follows: Is the eject mass always of order 0.01 solar mass ? What type of r-process elements are synthesized in the neutron-star mergers ? Is the gamma-ray burst always launched in the neutron-star merger ? Are electromagnetic counterparts in the ultraviolet, optical and infrared bands always similar to the previous event ? Does the effect of neutrino oscillation play a role ? What is the characteristic feature for the merger of black hole-neutron star binaries ?

From April of 2019, advanced LIGO and advanced VIRGO will start 3rd observational (O3) run for one year. The sensitivity of these detectors will be appreciably better than in the previous runs, and hence, we can expect that more neutron-star merger events will be observed. In addition, KAGRA plans to join O3 perhaps from early 2020. We will have a great opportunity to deeply understand the nature of the neutron-star merger (including black hole-neutron star merger) and the origin of r-process elements as well as the nature of neutron stars. For the forthcoming events, we need more sophisticated theoretical prediction for the neutron-star merger, mass ejection, r-process nucleosynthesis, and electromagnetic emission.

In this workshop, we invite several leading scientists working in neutron-star mergers, nucleosynthesis, and electromagnetic emission, aiming at enhancing the collaboration in the east Asia area. We focus in particular on predicting the observational feature for the next events.


Masaru Shibata (YITP/AEI)
Meng-Ru Wu (Institute of Physics, Academia Sinica)
Kenta Hotokezaka (Princeton University)