Astronomy Colloquium: Steve Rodney

Date: Fri. February 21st, 2020, 2:15 pm-3:30 pm
Location: Sears 552

Stellar Explosions and Cosmic Lenses

Steve Rodney (USC)

A new field of study is opening in astrophysics, at the intersection of strong gravitational lensing and stellar transient science.  Very rarely a supernova (SN) or other stellar transient happens to appear in nearly perfect alignment behind a foreground galaxy or cluster.  In this case the general relativistic effect of gravitational lensing may boost the transient’s apparent brightness by several magnitudes and cause it to appear as multiple images on the sky. Only a handful of these strongly-lensed transients have been observed to date, but the sample will soon grow to hundreds with upcoming wide-field surveys like LSST and WFIRST.  This new class of objects holds great promise for studying the physics of stellar explosions in the early universe and probing the distribution of dark matter in galaxies and clusters.  By measuring the delay in arrival time between any pair of gravitationally-lensed transient images, one can derive a distance ratio that is inversely proportional to the Hubble-Lemaître constant, H0—and completely independent of the local cosmic distance ladder.  I will review some of the prominent lensed transient discoveries of the past few years, and look ahead to how we can find and use these rare events in the next decade.