Astronomy began with time-dependent observations, when humankind first started to notice the changing skies and the motion of celestial bodies. In the modern era, time-domain observations are one of the main driving forces in astronomy, with the proliferation of large all-sky surveys, fast-response instrumentation, and global multi-wavelength and multi-messenger networks dedicated to catching astrophysical transient events. In the near future, we will be probing the Universe much deeper and in finer detail than ever before, with the unprecedented light-gathering power and angular resolution promised by the next generation of extremely large telescopes. As we are entering this exciting new era, transient astrophysics must also seize new opportunities by exploring hitherto uncharted regions of parameter space – in depth, time cadence, wavelength coverage, and spectroscopic and spatial resolution – and by leveraging cutting-edge technologies and instrumentation, along with novel techniques in observations, theory, and analysis. A strong synergy between observations and theory will certainly drive the field forward.
The landscape of observational astronomy in 2026 and onwards will be a thriving habitat for transient astrophysics. By that time, the Legacy Survey of Space and Time (LSST) at the Vera Rubin Observatory will have started science operations and delivered its first discoveries. This will be concurrent with new transient-optimized instrumentation such as the Son of X-Shooter (SOXS) spectrograph on the ESO New Technology Telescope (NTT). At that time, the community will also be preparing for the LIGO/Virgo/KAGRA O5 observing run with improved capabilities for gravitational wave detections, planned to start in 2027. Within a short couple of years, around 2028, the ESO Extremely Large Telescope (ELT), the first of the giant telescopes, will be commissioned and thus open completely unprecedented opportunities for observations in terms of depth and spatial resolution. During the very active period preceding and following 2026, a number of other facilities, many with significant components for time-domain astronomy, will be commissioned or launched, resulting in an unprecedented coverage of most of the electromagnetic spectrum – and more – by the mid-2030s. These include the Cherenkov Telescope Array (CTA) at very high-energy gamma rays; the Square Kilometer Array (SKA) in the radio; new space missions including UVEX and ULTRASAT in the ultraviolet; the Roman Space Telescope in the optical and near-infrared; THESEUS and NewAthena missions in the high energy domain; and the Laser Interferometer Space Antenna (LISA) in gravitational waves. ESO will also decide on the 2040s post-ELT projects between 2027-2028, which will make the Symposium timely for this discussion as well.
As exemplified by the gravitational wave event 170817 and the accompanying kilonova, rapid-timescale response on a global scale is critical for the fastest-evolving transients. The future facilities are expected to improve on this, along with a significant increase in the depth of observations. One example of an outstanding challenge in transient astrophysics is the identification of high-redshift supernovae associated with population III stars. Synergy between wide-field surveys and extremely large telescopes will be crucial for probing these events and their host stellar populations. Coordinated multiwavelength observations will also illuminate the nature of transients such as superluminous supernovae and fast blue optical transients (FBOTs), potentially powered by magnetars or central engines. Alongside these advancements, novel theoretical approaches are essential for interpreting and guiding the observations, addressing unresolved questions such as gamma-ray burst energy extraction and jet formation, and the origins of fast radio bursts.
With this Symposium, we thus aim to address the challenges presented by this new era by gathering together a balanced ensemble of researchers worldwide, with expertise on transient phenomena including supernovae, kilonovae, tidal disruption events, gamma-ray bursts, X-ray transients, fast radio bursts and various types of rare transients with debated origins, over a wide range of wavelengths from radio to infrared, optical and UV to X-rays and gamma-rays as well as in the gravitational-wave and neutrino domains. We will seek the insights of experts on a range of observational techniques from spectroscopy and polarimetry to interferometric observations providing the highest available angular resolution, as well as experts on modelling and simulations to explain the observations and to anticipate future discoveries of new types of transient events. As the new facilities are bound to bring about a flood of data that mere humans will have a hard time sifting through to find the most interesting events, we also aim to cover novel machine-learning methods and broker services that can optimize this process. The symposium will therefore consist of presentations providing a multi-wavelength and multimessenger view of the transient field, making use of the already-existing state-of-the-art instrumentation while looking into the technologies available in the near future and the best ways of using them. They will include highlights on intriguing individual events and their interpretations, as well as theoretical predictions showing us what to expect and where to look next, in preparation for a new era of discovery.
Being at the intersection of observations, theory, and computational techniques, this symposium offers a comprehensive overview and preview of the field, which will benefit the community and drive the science and technology forward. New insights will be emerging and collaborations forged, which in the end will be crucial for ensuring the optimum use of future facilities.
Key Topics:
- Multiwavelength and multimessenger observations of extragalactic transients
- Rates and physical mechanisms of supernovae, tidal disruption events, and related transients
- Physics of the transients and their progenitor systems, remnants, and host galaxies
- Transient surveys, statistical analyses and machine-learning techniques
- Opportunities and challenges offered by new ground-based and space instrumentation with time-domain coverage
- Intermediate-sized telescopes in the era of extremely large telescopes
- Strategies in rapid and multiwavelength observations of fast transients across all wavebands from gamma-ray bursts to fast radio bursts
- Novel theoretical approaches in multi-dimensional explosion modeling
- Central engine activities, accretions, and shocks as power sources in transients
- Citizen science and community involvement in transient science