Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. III. Optical Variability and X-ray/UV/Optical Correlations
| Autor: | Alexei V. Filippenko, Mohan Ganeshalingam, Brandon J. Swift, Ari Laor, E. C. Moran, Louis-Benoit Desroches, Kirpal Nandra, Weidong Li, Misty C. Bentz, P. M. O'Neill, Dan Maoz, Shai Kaspi, Bradley M. Peterson, Luis C. Ho |
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| Jazyk: | angličtina |
| Rok vydání: | 2006 |
| Předmět: |
Physics
Active galactic nucleus Astrophysics::High Energy Astrophysical Phenomena Astrophysics (astro-ph) Balmer series FOS: Physical sciences Astronomy and Astrophysics Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics Light curve Galaxy Spectral line Photometry (optics) Wavelength symbols.namesake Space and Planetary Science symbols Astrophysics::Solar and Stellar Astrophysics Emission spectrum Astrophysics::Galaxy Astrophysics |
| Popis: | 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-band and B-band photometry, and spectra over the range 3500-6800 Angstroms. 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. Inter-band cross-correlations suggest that the optical continuum emission lags behind the UV continuum emission by 24 +7/-9 min, and that the optical continuum emission lags behind the X-ray continuum emission by 44 +/- 13 min, 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. 29 pages, 16 figures, emulateapj, accepted for publication in ApJ |
| Databáze: | OpenAIRE |
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