This session aims to bring together a diverse range of experts to disseminate knowledge and promote discussion on the interpretation of kilonovae, in an effort to establish what we already (think we) know, summarise what key questions remain unanswered, and determine what can be gleaned from future observations and theoretical models.

The discovery of the first (spectroscopically) confirmed kilonova event by the coincident detection of gravitational waves (GW170817), gamma rays (GRB170817A) and UV?optical?IR radiation (AT2017gfo) ushered in the field of multi-messenger kilonova science. Since this historic event, many studies have substantially contributed to advancing our understanding of the explosive, fast-evolving kilonova transients that are produced by neutron star mergers. Kilonovae provide us with an unrivalled opportunity to study the dynamics of matter under extreme conditions. The neutron-rich conditions in the rapidly expanding ejecta enable the rapid neutron-capture process (r-process) to take place. Extensive observations of AT2017gfo provide insights into r-process nucleosynthesis, as well as the still-mysterious high-density equation of state.

Further gravitational wave events have been scarce, and of the ones that have been detected, no optical counterpart has been identified. Kilonovae are rare, difficult to discover, and necessitate rapid response and high-cadence observations. With LIGO?Virgo?KAGRA?s fourth observing run having ended, the community needs to seize alternative discovery pathways. In addition to gamma-ray satellites, we now have access to the X-ray satellites SVOM and Einstein Probe, which together can detect high-energy signals from neutron star mergers. Additionally, Rubin Observatory?s LSST survey is currently due to commence in early 2026, and promises to unearth an avalanche of new transient phenomena, including kilonovae. How exactly the community handles such high volumes of data (and disentangles kilonova signals) from multiple different instruments spanning vast ranges of the electromagnetic spectrum, is an ongoing, but exciting, problem. And, once observed and processed, how well is the community placed to interpret such observations? Atomic data remains a limiting factor in interpreting data, although recent works are leading to substantial improvement in this field. Additional advancements in hydrodynamic simulations and radiative transfer also hold promise.

Key goals of this special session encompass multiple facets of kilonova science. Namely, we seek to establish what is needed to advance our understanding of kilonovae, ascertain how well elemental abundances can be constrained in individual kilonova events, and determine whether we can place constraints on high-density physics. We anticipate accepting contributions from a broad range of topics, including, but not limited to: multi-wavelength and multi-messenger observations and their interpretation; radiative transfer simulations; neutron star merger simulations; atomic data advancements; r-process nucleosynthesis.

Programme

• multi-wavelength and multi-messenger observations and their interpretation
• neutron star merger simulations and radiative transfer simulations
• atomic data advancements and r-process nucleosynthesis

Invited speakers

Scientific organisers

• James Gillanders (University of Oxford)
• Christine Collins (Trinity College Dublin)
• Mattia Bulla (University of Ferrara)
• Oliver Just (GSI Helmholtz Centre for Heavy Ion Research)
• Cathy Ramsbottom (Queen?s University Belfast)

Contact

For all queries, email james.gillanders @ physics.ox.ac.uk