2006/06/20 by Louis‐Benoit Desroches, Louis-Benoit Desroches, Alexei V. Filippenko +18 · 1 citation
Physics and Astronomy · #Active galactic nucleus #Adaptive optics and wavefront sensing #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Balmer series #Doubly ionized oxygen #Emission spectrum #Galaxies: Formation, Evolution, Phenomena #Galaxy #Light curve #Optics #Photometry (optics) #Physics #Reverberation mapping #Spectral line #Stars #Wavelength #astro-ph
paper · pdf · doi:10.1086/507263
published as Astrophys.J.650:88-101,2006 · 29 pages, 16 figures, emulateapj, accepted for publication in ApJ
arxiv created 2006/06/20 · openalex publication_date 2006/10/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present optical observations of the low-luminosity Seyfert 1 nucleus of NGC 4395, as part of a multiwavelength reverberation-mapping program. Observations were carried out over two nights in 2004 April at Lick, Wise, and Kitt Peak Observatories. We obtained V - and B -band photometry, and spectra over the range 3500-6800 Å. Simultaneous Hubble Space Telescope UV and Chandra X-ray observations are presented in companion papers. Even though NGC 4395 was in an extremely low state of activity, we detect significant continuum variability of 2%-10%, increasing toward shorter wavelengths. The continuum light curves, both spectroscopic and photometric, are qualitatively similar to the simultaneous UV and X-ray light curves. Interband cross-correlations suggest that the optical continuum emission lags behind the UV continuum emission by 24 minutes, and that the optical continuum emission lags behind the X-ray continuum emission by 44 ± 13 minutes, consistent with a reprocessing model for active galactic nucleus emission. There are also hints of Balmer emission lines lagging behind the optical continuum by an amount slightly larger than the emission-line lag detected in the UV. These results are all similar to those of other Seyfert 1 nuclei. The emission-line lag yields a mass measurement of the central black hole, which although not very significant, is consistent with the value derived from the simultaneous UV data.