Space Telescope and Optical Reverberation Mapping Project. II. Swift and HST Reverberation mapping of the accretion disk of NGC 5548
- Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States)
- Spectral Sciences Inc., 4 Fourth Avenue, Burlington, MA 01803 (United States)
- SUPA Physics and Astronomy, University of St. Andrews, Fife, KY16 9SS Scotland (United Kingdom)
- University of Southampton, Highfield, Southampton, SO17 1BJ (United Kingdom)
- Department of Astronomy, The Ohio State University, 140 W 18th Ave, Columbus, OH 43210 (United States)
- Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Gran Bretana N 1111, Playa Ancha, Valparaíso (Chile)
- Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom)
- University of Leicester, Department of Physics and Astronomy, Leicester, LE1 7RH (United Kingdom)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- Department of Astronomy and Astrophysics, Eberly College of Science, Penn State University, 525 Davey Laboratory, University Park, PA 16802 (United States)
- Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
- Space Science Center, Morehead State University, 235 Martindale Drive, Morehead, KY 40351 (United States)
- Department of Physics and Institute of Theoretical and Computational Physics, University of Crete, GR-71003 Heraklion (Greece)
Recent intensive Swift monitoring of the Seyfert 1 galaxy NGC 5548 yielded 282 usable epochs over 125 days across six UV/optical bands and the X-rays. This is the densest extended active galactic nucleus (AGN) UV/optical continuum sampling ever obtained, with a mean sampling rate <0.5 day. Approximately daily Hubble Space Telescope UV sampling was also obtained. The UV/optical light curves show strong correlations (r{sub max}=0.57−0.90) and the clearest measurement to date of interband lags. These lags are well-fit by a τ∝λ{sup 4/3} wavelength dependence, with a normalization that indicates an unexpectedly large disk radius of ∼0.35±0.05 lt-day at 1367 Å, assuming a simple face-on model. The U band shows a marginally larger lag than expected from the fit and surrounding bands, which could be due to Balmer continuum emission from the broad-line region as suggested by Korista and Goad. The UV/X-ray correlation is weaker (r{sub max}<0.45) and less consistent over time. This indicates that while Swift is beginning to measure UV/optical lags in general agreement with accretion disk theory (although the derived size is larger than predicted), the relationship with X-ray variability is less well understood. Combining this accretion disk size estimate with those from quasar microlensing studies suggests that AGN disk sizes scale approximately linearly with central black hole mass over a wide range of masses.
- OSTI ID:
- 22883058
- Journal Information:
- Astrophysical Journal, Vol. 806, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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