Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XVI. A 13 Year Study of Spectral Variability in NGC 5548

By B. Peterson, P. Berlind, R. Bertram, K. Bischoff, N. Bochkarev, N. Borisov, A. Burenkov, M. Calkins, Luis Carrasco, V. Chavushyan and 31 more. 2002

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We present the final installment of an intensive 13 year study of variations of the optical continuum and broad Hβ emission line in the Seyfert 1 galaxy NGC 5548. The database consists of 1530 optical continuum measurements and 1248 Hβ measurements. The Hβ variations follow the continuum variations closely, with a typical time delay of about 20 days. However, a year-by-year analysis shows that the magnitude of emission-line time delay is correlated with the mean continuum flux. We argue that the data are consistent with the simple model prediction between the size of the broad-line region and the ionizing luminosity, r ∝ L. Moreover, the apparently linear nature of the correlation between the Hβ response time and the nonstellar optical continuum Fopt arises as a consequence of the changing shape of the continuum as it varies, specifically Fopt ∝ F.

Subfields: Astronomy and Astrophysics

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Citations in the corpus

Systematic effects in measurement of black hole masses by emission-line reverberation of active galactic nuclei: Eddington ratio and inclination (2006, background): “In addition, AGNs show a relationship between BH mass and the host-galaxy bulge velocity dispersionσ∗ (Gebhardt et al. 2000b; Ferrarese et al. 2001; Onken et al. 2004; Nelson et al. 2004) that is consistent with this same correlation, the MBH–σ∗ relationship, that is observed in quiescent galaxies (”
A LARGE SYSTEMATIC SEARCH FOR CLOSE SUPERMASSIVE BINARY AND RAPIDLY RECOILING BLACK HOLES (2011, unknown): “…data available today indicate that the variability properties of this object do not support such an interpretation (e.g., Wanders & Peterson 1996; Peterson et al. 2002; Sergeev et al. 2007). very recent study, Tsalamantza et al. (2011) have used an automatic method to search systematically…”
Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation-Mapping Database (2004, methodology): “The justification for this assumption is simply that a virial relationship between time delay and line width has already been established for several objects (Peterson & Wandel 1999, 2000; Onken & Peterson 2002; Kollatschny 2003).”
QUANTIFYING QUASAR VARIABILITY AS PART OF A GENERAL APPROACH TO CLASSIFYING CONTINUOUSLY VARYING SOURCES (2009, background): “…for MRK 279 (Santos-Lleó et al. 2001), MRK 509 (Carone et al. 1996), NGC 3783 (Stirpe et al. 1994), NGC 4051 (Peterson et al. 2000), and NGC 5548 (Peterson et al. 2002, and references therein), and then either subtract the remaining host flux in the spectroscopic apertures or add in the host…”
REVERBERATION MAPPING MEASUREMENTS OF BLACK HOLE MASSES IN SIX LOCAL SEYFERT GALAXIES (2010, background): “…long-term secular trends, since the relationship between the measured continuum and the ionizing continuum responsible for producing the emission lines may not be a linear one (Peterson et al. 2002), and the exact response of the line depends on the detailed structure and dynamics of the BLR. 4.”
A Reverberation-based Mass for the Central Black Hole in NGC 4151 (2006, background): “…analysis, measuring the line widths in the variable part of the emission line, and accounting for the fact that changes in the mean luminosity of the source could cause emission-line time lags to vary over longer time scales than the reverberation time scale (Peterson et al. 2002).”
THE LICK AGN MONITORING PROJECT: BROAD-LINE REGION RADII AND BLACK HOLE MASSES FROM REVERBERATION MAPPING OF Hβ (2009, background): “The point denoted as “Year 12” is the monitoring dataset from the year 2000 and is known to be very poorly sampled and to yield ambiguous results when the Hβ light curve is cross-correlated with the continuum light curve (Peterson et al. 2002).”
Supermassive Black Holes in Galactic Nuclei: Past, Present and Future Research (2004, background): “In NGC 5548, the only AGN for which there is sufficient information on the long term behavior of a single line (Hβ) to measure both the line widths and lags as a function of time, the lag is observed to become longer as the continuum brightens (Peterson et al. 2002).”
ARE THE VARIATIONS IN QUASAR OPTICAL FLUX DRIVEN BY THERMAL FLUCTUATIONS? (2009, unknown): “— (1) Giveon et al. 1999 (2) Geha et al. 2003 (3) Stirpe et al. 1994 (4) Peterson et al. 2000 (5) Kaspi et al. 1996 (6) Santos-Lleo et al. 2001 (7) Peterson et al. 2002 (8) Carone et al. 1997 (9) Shemmer et al. 2001 (10) Collier et al. 1998 Note.”
The Relationship between Luminosity and Broad-Line Region Size in Active Galactic Nuclei (2005, methodology): “For example, the covering factor and mean gas 8 The 0.53 slope was found by scaling the relation for the optical luminosity (0.95) by the slope of the relation between the UV and the optical luminosities, which Peterson et al. (2002) find to be 0.56.”
What the Optical Recombination Lines Can Tell Us about the Broad-Line Regions of Active Galactic Nuclei (2004, background): “In fact, for this particular model, a continuum state that is a factor of 12 times brighter than the low state6 produces a 6 Such a high state in NGC 5548 was recorded in 1984 (Wamsteker et al. 1990) and again in 1998 (Peterson et al. 2002).”