Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. I. A Reverberation-based Measurement of the Black Hole Mass
Creators:Peterson, Bradley M.
Bentz, Misty C.
Filippenko, Alexei V.
Ho, Luis C.
Moran, Edward C.
Pogge, Richard W.
Quillen, Alice C.
quasars: emission lines
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Publisher:American Astronomical Society
Citation:Bradley M. Peterson et al, "Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. I. A Reverberation-based Measurement of the Black Hole Mass," The Astrophysical Journal 632, no. 2 (2005), doi:10.1086/444494
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 M_BH = (3.6 ± 1.1) × 105 Msun. The observations consist of two visits of five 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 λ1549 showed corresponding variations large enough to reliably determine the emission-line lag, which was measured to be of order 1 hr for both visits. The size of the C IV-emitting region is about a factor of 3 smaller than expected if the slope of the broad-line region radius-luminosity relationship is identical to that for the Hβ emission line. NGC 4395 is underluminous even for its small black hole mass; the Eddington ratio of ~1.2 × 10^-3 is lower than that of any other active galactic nucleus for which a black hole mass measurement has been made by emission-line reverberation
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