The Optical Gravitational Lensing Experiment (OGLE) started at Las Campanas Observatory in 1992 with a pilot monitoring programme of two million stars in the Galactic Bulge. It is still operating today, collecting time-domain photometric data of a billion stars from the densest regions in the southern sky. Among its main achievements are discoveries of thousands of microlensing events, a few dozen extrasolar planets and candidates for black holes, a million variable stars, and thousands of quasars and supernovæ. It has made a major contribution to the studies of the dark-matter content of the Milky Way halo, the structure of the Galactic Bulge, the Magellanic Clouds, and new classes of variable stars. In this its 25th anniversary year, we presented a selection of the major scientific highlights of OGLE.

AGNs are an inherently variable population but the physical mechanisms behind optical variability remain poorly constrained or not well understood. The advent of large archival collections of astronomical time series together with new analysis techniques is now driving systematic explorations of these phenomena. They reveal both population behaviours and individual extreme sources. This talk reviewed how the Catalina Real-time Transient Survey is transforming our knowledge of AGN behaviour, mentioning in particular the new CRTS Southern Sky Quasar Catalogue (which covers −70 < Dec < 0 down to V ∼ 19), and the potential of the Zwicky Transient Facility for further discoveries.

The revolution in time-domain astronomy has arrived. Large-scale surveys are detecting events at an unparallelled rate, and discoveries of new and exotic objects abound. In just a few short years, the Large Synoptic Survey Telescope will begin operations in Chile. At that point, the rate of production of time-domain events will jump by a factor of at least a hundred. The traditional techniques of handling each detection individually will not scale to those current and future productions. The ANTARES project is a joint venture between NOAO and the University of Arizona Computer Science Department to develop a software infrastructure system to process time-domain events automatically at the scale and rate that LSST will generate them.

Explosive stellar transients arise from diverse situations, including deaths of massive stars, a variety of thermonuclear outbursts, and compact-object mergers. Stellar interactions are heavily implicated in explaining the observed populations of events, and not only those where binarity is obviously involved. Relationships between these classes probably help to elucidate our understanding; for example; the production of double neutron-star mergers from field binaries is thought to be heavily biased towards routes involving stripped core-collapse supernovæ. As we gain an ever more synoptic view of the changing sky, theorists should be mindful of developing an ability to take robust quantitative advantage of the available population information to help constrain the physics. This is complementary to aiming for deep understanding of individual events.

Radio astronomy is currently exploring an intriguing new phase-space that probes the dynamic Universe on time-scales of milliseconds. Recent developments of sensitive, high-time-resolution instruments has made possible the discovery of millisecond-duration fast radio bursts (FRBs). The FRB class encompasses a number of single pulses, each unique in its own way, hindering a consensus for their origin. The key to de-mystifying FRBs lies in discovering many of them in real time in order to identify commonalities. The recently upgraded UTMOST, in Australia, has undergone a digital back-end transformation to rise as a fast-transient detection machine. The talk presented the first interferometric detections of FRBs made by this telescope at less that a quarter of its target sensitivity, placing their origin beyond the near-field region of the telescope and thus ruling out local sources of interference as a possible origin. Despite rigorous follow-ups, none of the FRBs observed with the upgraded UTMOST has been seen to repeat, suggesting the possibility of there being two independent classes of FRBs with two classes of possible progenitors. The talk then discussed the recent developments in the field, some of the open questions in FRB astronomy, and how the next-generation telescopes are vital in the quest to understand this enigmatic population.

The blue continuum of the eclipsing polar UZ For is dominated by single- or double-peaked emission from He ii, He i and the Balmer lines. The red spectrum shows weak emission from the Na i doublet at λ 8183 and 8194 Å and strong emission from the Ca ii lines at λ 8498 and 8542 Å. Doppler tomography of the strongest emission features reveals the presence of emission from the irradiated face of the secondary star, the threading region, and the ballistic and magnetically confined accretion stream. We have obtained 28 new eclipse times of UZ For during 2011–2016 as part of our eclipse timing follow-up programme to test the two-planet model proposed to explain variations in the eclipse times of UZ For.

This talk introduced and described the Next Generation Transit Survey (NGTS), which is a new ground-based transit survey operating at the ESO Paranal Observatory. NGTS has been designed to achieve better photometric precision than previous ground-based surveys; it aims to detect Neptune-sized planets around Sun-like stars, and sub-Neptunes around M dwarfs that are sufficiently bright for radial-velocity confirmation and mass determination. NGTS is also optimised for ground-based follow up of exoplanet candidates from TESS and PLATO. I presented early results from the survey, and described the status of our HARPS radial-velocity and SAAO photometric follow-ups of exoplanet candidates.

Stars are the main ingredients of galaxies, and the sites of the creation of most chemical elements in our universe. The knowledge that we gain from studying nearby resolved stellar populations assists directly our ability to measure the properties of distant galaxies. The overall objective of this project is to study galaxy formation and evolution in a complete environment of the dwarf galaxies in the Local Group, by using the same methods for all of them. For that purpose, we used the INT to conduct a monitoring survey of the majority of Local-Group dwarf galaxies in order to identify the most evolved AGB stars that are long-period variables (LPV). LPV stars reach their maximum brightness amplitudes at optical wavelengths, owing to changes in temperature. They trace stellar populations as young as ∼30 Myr up to as old as ∼10 Gyr, and identifying them is one of the best ways of reconstructing star-formation history using a method that we have developed and applied successfully to other Local-Group galaxies. Since the luminosity variations span 100–1000 days, we planned observations over 10 epochs, spaced ∼3 months apart; 9 epochs of data have so far been obtained.