A LOW-MASS BLACK HOLE IN THE NEARBY SEYFERT GALAXY UGC 06728

We present the results of a recent reverberation mapping campaign for UGC 06728, a nearby low-luminosity Seyfert 1 in a late-type galaxy. Nightly monitoring in the spring of 2015 allowed us to determine an Hβ time delay of days. Combined with the width of the variable Hβ line profile, we determine a black hole mass of . We also constrain the bulge stellar velocity dispersion from higher-resolution long-slit spectroscopy along the galaxy minor axis and find km s−1. The measurements presented here are in good agreement with both the relationship and the relationship for active galactic nuclei. Combined with a previously published spin measurement, our mass determination for UGC 06728 makes it the lowest-mass black hole that has been fully characterized, and thus an important object to help anchor the low-mass end of black hole evolutionary models.