CHRISTOPHER KOCHANEK, OHIO STATE UNIVERSITY

PRINCETON ASTRONOMY COLLOQUIUM - APRIL 13, 2004

ABSTRACT

Time Variability In Gravitational Lenses

The image fluxes in gravitational lenses vary due to both brightness variations in the source and microlensing of the images by the stars in the lens galaxy. Time delay measurements from the intrinsic variability and the statistics of the microlensing variability constrain the total surface density and the fraction of that density in stars near the lensed images. Current results are puzzling, particularly if the Hubble constant is 72 km/s Mpc -- early-type galaxy halos must be less massive and more inhomogeneous than expected. I describe a new lens monitoring program designed to address these issues.