The mass of the black hole in the Seyfert 1 galaxy NGC 4593 from reverberation mapping

We present new observations leading to an improved black hole mass estimate for the Seyfert 1 galaxy NGC 4593 as part of a reverberation-mapping campaign conducted at the MDM Observatory. Cross-correlation analysis of the Ho emission-line light curve with the optical continuum light curve reveals an emission-line time delay of tau(cent) = 3.73 +/- 0.75 days. By combining this time delay with the H beta line width, we derive a central black hole mass of M-BH = (9.8 +/- 2. 1) x 10(6) M circle dot, an improvement in precision of a factor of several over past results.