Speaker: Pat Kelly (University of Minnesota)

Host: Charlotte Wood

Title: Lensed Transients and Quick Response Telescopes

Abstract: HST and now JWST observations of galaxy-cluster gravitational lenses have revealed several new phenomena at high redshift. The first is multiply imaged supernovae, whose staggered arrivals at Earth offer an exciting new avenue for measuring the Hubble constant and providing a new test of lens models. I will present observations of a multiply imaged lensed supernova at redshift z~3 which was imaged at only a single epoch by HST. Nonetheless, gravitational time delays among its images allow us to reconstruct the SN’s light curve beginning with hours of explosion. We use the observations to constrain the exploding red supergiant’s pre-explosion radius, and place new constraints on the cosmic star-formation history. Observations using HST and now JWST have revealed a growing sample of extremely magnified individual stars at redshifts greater than one. I will describe an ongoing large Hubble program called Flashlights that is building a sample of such stars.  Finally, I will briefly describe a project called TURBO that will catch nearby supernovae at first light and responds within several seconds to alerts.