Astrophysics & Particle Physics-APPC 2026

Kilonovae are rare, highly energetic astrophysical phenomena caused by the collision of two neutron stars or a neutron star with a black hole. The collisions create a temporary, but strong, release of light and other electromagnetic radiation, along with the emission of gravitational waves, making them prime targets in multi-messenger astronomy.Kilonovae are central to heavy element nucleosynthesis. The neutron-rich material expelled in the merger is then subject to rapid neutron capture (r-process), forming some of the universe's heaviest elements, including gold, platinum, and uranium.

These processes add greatly to the chemical enrichment of galaxies.Observationally, kilonovae are seen by optical, infrared, and X-ray telescopes as transient light sources. They are usually linked to short gamma-ray bursts (GRBs), brief instants of intense high-energy radiation that result from relativistic jets released upon the merger. The multiplexing of electromagnetic and gravitational-wave signals makes it possible to localize precisely and study in detail these exotic events.Gravitational-wave detectors, like LIGO and Virgo, have made kilonova discovery possible through direct observation of neutron star mergers.

The first firmly detected kilonova, GW170817, showed the concomitant detection of gravitational waves and electromagnetic radiation, ushering in an era of multi-messenger astrophysics.Kilonovae also shed light on the physics of extreme densities, strong magnetic fields, and relativistic dynamics. The study of these events assists scientists with the behavior of matter at nuclear density, the creation of compact objects, and the physics of high-energy transients in the universe. By exploring kilonovae, astronomers acquire pivotal information regarding stellar endpoints of evolution, nucleosynthesis, gravitational physics, and interactions between compact objects and their surroundings, and thus kilonovae become a cornerstone of contemporary high-energy astrophysics and multi-messenger astronomy.