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.