The Mass of the Central Black Hole in the Nearby Seyfert Galaxy NGC5273
  We present the results of a reverberation-mapping program targeting NGC5273,
a nearby early-type galaxy with a broad-lined active galactic nucleus. Over the
course of the monitoring program, NGC5273 showed strong variability that
allowed us to measure time delays in the responses of the broad optical
recombination lines to changes in the continuum flux. A weighted average of
these measurements results in a black hole mass determination of $M_{\rm BH} =
(4.7 \pm 1.6) \times 10^6$ M$_{\odot}$. An estimate of the size of the black
hole sphere of influence in NGC5273 puts it just at the limit of the resolution
achievable with current ground-based large aperture telescopes. NGC5273 is
therefore an important future target for a black hole mass determination from
stellar dynamical modeling, especially because it is the only nearby early-type
galaxy hosting an AGN with a reverberation-based mass, allowing the best
comparison for the masses determined from these two techniques.
