2005/06/30 by Bradley M. Peterson, Misty C. Bentz, Louis-Benoit Desroches +8 · 2 citations
Physics and Astronomy · #astro-ph
paper · pdf · doi:10.1086/444494
published as Astrophys.J.632:799-808,2005; Erratum-ibid.641:638,2006 · This replacement is an erratum to be published in The Astrophysical Journal. 3 pages, with one replacement figure and one replacement table
arxiv created 2005/12/15 · arxiv updated 2009/12/01
A reverberation-mapping program on NGC 4395, the least-luminous known Seyfert 1 galaxy, undertaken with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, yields a measurement of the mass of the central black hole of 360,000 solar masses. The observations consist of two visits of 5 orbits each, in 2004 April and July. During each of these visits, the UV continuum varied by at least 10% (rms) and only C IV 1549 showed corresponding variations large enough to reliably determine the emission-line lag, which was measured to be of order one hour for both visits. The size of the C IV-emitting region is about a factor of three smaller than expected if the slope of the broad-line region radius-luminosity relationship is identical to that for the H-beta emission line. NGC 4395 is underluminous even for its small black hole mass; the Eddington ratio of 0.0012 is lower than that of any other active galactic nucleus for which a black hole mass measurement has been made by emission-line reverberation.