Transients and time domain astrophysics

Abstract

Time Domain Astronomy (TDA) has ushered in a new era of cosmic exploration. This has been possible with the advanced sensitive surveys that have allowed the discovery and classification of transients to reach unprecedented levels. Over the past decades, numerous classes of stellar transients, including various types of Supernovae (SNe), Novae, Gamma Ray Bursts (GRBs), Electromagnetic counterparts of Gravitational Wave (EMGW) events, Tidal Disruption Events (TDEs), Fast Radio Bursts (FRBs) and many more have been discovered. Of these, detecting the first EMGW event (GW170817/GRB 170817A) and the associated kilonova (AT2017gfo) resulting from a compact object merger stands out as a groundbreaking achievement. A coordinated multi-wavelength approach is crucial for studying these transients, as they exhibit unique behaviours across the different bands of the EM spectrum. This chapter presents an overview of the current understanding and open questions of a few select classes of transients. We highlight the focus areas of TDA in terms of their scientific merit based on existing and future facilities, as well as nationwide and international collaborations. The recommendations made in this chapter are aligned to meet the requirements of all TDA studies.