Description
Einstein Probe has opened a new window into X-ray transients, particularly the diverse sample of fast X-ray transients (FXTs) that it is uncovering. These FXTs show a wide range of properties and some have been linked to known transient classes including gamma-ray bursts (GRBs). In this talk, I will discuss one recently detected FXT with unique and fascinating behaviour, EP250108a/SN 2025kg or the ‘kangaroo’. EP250108a is an unusually long FXT and its optical characteristics are similarly atypical with an early fast cooling thermal phase followed by a type Ic broad lined supernova. I will explore how the X-ray, optical and radio data combine to show that this early emission could be one of the first observed examples of a shocked cocoon resulting from a trapped jet. I will also present our analysis of the supernova itself, which closely resembles supernovae linked to GRBs, and discuss the implications for the progenitor system. Finally, I will compare to other fast transients and discuss the broader implications for the wider FXT and GRB populations uncovered by this unique event.
