Electromagnetic Signatures of r-process Nucleosynthesis in Neutron Star Binary Mergers (INT-17-2b)

Overview

The impending detection of coalescing neutron star (NS) binaries by Advanced LIGO / Virgo offers a tremendous opportunity for nuclear physics and astrophysics. Gravitational waves (GW) from these mergers encode information on NS masses, radii, tidal deformability, and the maximum NS mass, all of which constrain the nuclear equation of state. Follow up observations across the electromagnetic (EM) spectrum may lead to the discovery of an optical/infrared counterpart powered by the radioactive decay of r-process isotopes. The light curves and spectra of these so-called kilonovae carry information on the amount and composition r-process nuclei, offering detailed insight into galactic chemical enrichment and the extreme nuclear and neutrino physics involved in NS mergers.

The intrinsically multi-physics and multi-messenger aspects of neutron star binary inspirals emphasize the need for fruitful inter-disciplinary interaction, and provides the backbone of the program. Predictions of EM counterparts are currently limited by the uncertain binary progenitor population and the treatment of nuclear and atomic physics. The kilonova emission is particularly sensitively to the composition of the ejecta, especially the presence of lanthanide and actinide ions which have unusually high opacities due to a complex electronic structure. More accurate predictions of nucleosynthetic yields can be aided by incorporating into simulations the new data on very neutron rich isotopes from experiments like the upcoming Facility for Rare Isotope Beams (FRIB). Improving kilonova opacities will require quantum many-body atomic structure calculations that are calibrated to experimentally measured atomic transitions in laser plasmas.

The program will bring together nuclear physicists, astrophysicists, atomic physicists, observational astronomers and gravitational-wave physicists to address key issues and identify new directions in the study of the EM signatures of NS mergers. Currently, the physics of NS mergers are being studied by several groups using remarkably high-fidelity numerical simulations of the merger and remnant dynamics, and the subsequent nucleosynthesis and radiative transport. At the same time, observers are employing a world-wide network of telescopes to survey large swaths of the LIGO localization regions in search of an EM counterpart. The successful detection and interpretation of an EM counterpart will greatly benefit from coordinating observational strategies with improved theoretical predictions.

Organization

The schedule for the 4-week backbone program is designed to foster interactions among theorists, experimentalists and observers, thus facilitating inter-disciplinary collaborations and discussions that might otherwise not take place. Due to space constraints, we are limited to host ~20 long-term participants at any given time. To allow for greater participation, a more intensive workshop for a larger number of participants during the second week will bring together experts working on all aspects of the EM signals of NS mergers.

A summary of the focus topics for each week is given below, although we hope to maintain a broad range of expertise throughout all weeks of the program:

Week 1 (7/24 - 7/28): Binary formation channels, progenitors, galactic chemical evolution and metal-poor stars, EM follow-up observations

Week 2 (7/31 -8/4): Workshop Observational Signatures of r-process Nucleosynthesis in Neutron Star Mergers.

There will be a $40 registration fee to attend the workshop. The registration fee includes participation in the workshop, lectures, and coffee breaks.

During weeks 1,3, and 4, an emphasis will be placed on pedagogical talks, followed by ample time for open discussion and free collaboration. The workshop on week 2 will feature more talks as well as panel discussions.