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  • The ever-changing Universe

    Dr David Bersier

    The Universe is an extremely dynamic place, with change occurring on time scales from less than a second to billions of years. A change in the observable properties of an object (appearance, brightness, position, velocity, etc.) contains information on the structure and physics of this object. Change is thus a powerful way to understand the physical laws governing the behaviour of astronomical sources. This is largely why there are nowadays many observational programmes devoted to observing the sky on a regular basis to detect variable and transients phenomena. Examples include the ESA mission Gaia, the gamma-ray observatory Swift, and ground-based optical surveys such as Pan-STARRS, iPTF, and ASAS-SN.

    This project is centred on the All-Sky Automated Survey for Supernovae ASAS-SN. It uses small telescopes in Hawaii and Chile to observe the whole sky every other night. While finding less transients than other, deeper surveys, all ASAS-SN transients are bright and can be easily followed with other facilities, leading to a rich collection of follow-up data. In particular, we are using the Liverpool Telescope to obtain light curves and spectra of particularly interesting transients such as supernovae (SNe) and tidal disruption events (TDEs, stars ripped appart by a supermassive black hole).

    This project will focus on extreme and rare types of transients. In particular, ASAS-SN has already found several nearby (hence bright) TDEs that have been observed extensively. One goal of this project is to obtain observations of TDEs discovered by ASAS-SN, analyse the multi-wavelength data (UV, optical, X-ray) and paint a comprehensive picture of each event. Other interesting transients will be either very bright or very faint core-collapse supernovae where, again, a large multi-wavelength data set will be collected and analysed.