Abstract:

The Neil Gehrels Swift observatory, a multi-wavelength telescope originally dedicated for gamma-ray burst (GRB) study, has been observing the transient sky for 21 years. The Burst Alert Telescope (BAT) onboard Swift is a wide-field hard X-ray instrument designed for detecting GRBs and mapping the hard X-ray sky. To date, BAT has detected over 1700 GRBs, with about one-third of them have redshift measurements ranging from z=0.01 to z=9.38. In addition, Swift spends a majority of time observing sources beyond GRBs, such as supernovae, gravitational waves, tidal disruption events, fast radio bursts, X-ray binaries, AGNs, etc. With over two decades of observation, BAT provides unprecedented survey data for thousands of X-ray sources on time scales from minutes to years. In this talk, I will present summaries of the mission-long BAT observations for both GRBs and other hard X-ray sources. I will also discuss what we have learned and what lies ahead.