X-Ray and Optical Variability in NGC 4051 and the Nature of Narrow-Line Seyfert 1 Galaxies

By B. Peterson, I. McHardy, B. Wilkes, P. Berlind, R. Bertram, M. Calkins, S. Collier, J. Huchra, S. Mathur, I. Papadakis and 7 more. 2000

174 citations recorded by the source corpus.

We report on the results of a three-year program of coordinated X-ray and optical monitoring of the narrow-line Seyfert 1 galaxy NGC 4051. The rapid continuum variations observed in the X-ray spectra are not detected in the optical, although the time-averaged X-ray and optical continuum fluxes are well correlated. Variations in the flux of the broad Hβ line are found to lag behind the optical continuum variations by 6 days (with an uncertainty of 2-3 days), and combining this with the line width yields a virial mass estimate of ~1.1 × 106 M☉, at the very low end of the distribution of active galactic nucleus masses measured by line reverberation. Strong variability of He II λ4686 is also detected, and the response time measured is similar to that of Hβ but with a much larger uncertainty. The He II λ4686 line is almost 5 times broader than Hβ, and it is strongly blueward asymmetric, as are the high-ionization UV lines recorded in archival spectra of NGC 4051. The data are consistent with the Balmer lines arising in a low-to-moderate-inclination disklike configuration and the high-ionization lines arising in an outflowing wind, of which we observe preferentially the near side. Previous observations of the narrow-line region morphology of this source suggest that the system is inclined by ~50°, and if this is applicable to the broad Hβ-emitting region, a central mass of ~1.4 × 106 M☉ can be inferred. During the third year of monitoring, both the X-ray continuum and the He II λ4686 line went into extremely low states, although the optical continuum and the Hβ broad line were both still present and variable. We suggest that the inner part of the accretion disk may have gone into an advection-dominated state, yielding little radiation from the hotter inner disk.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/3f30005e169d0f5b7afb4cd49e5e5793db0c10fa

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In Astronomy and Astrophysics

1. Jenny E. Greene
2. B. Peterson
3. Luis C. Ho
4. H. Netzer
5. T. Treu
6. J. Woo
7. A. C. Fabian
8. D. M. Alexander

Citations in the corpus

• THE LICK AGN MONITORING PROJECT: BROAD-LINE REGION RADII AND BLACK HOLE MASSES FROM REVERBERATION MAPPING OF Hβ (2009, background): “The existence of a “virial” relationship between time lag and line width,v ∝ τ−0.5, has been clearly shown in NGC 5548 (Peterson & Wandel 1999), and has been in seen in numerous other objects (Peterson et al. 2000; Onken & Peterson 2002; Kollatschny 2003), upholding this basic assumption.”
• Supermassive Black Holes in Galactic Nuclei: Past, Present and Future Research (2004, background): “For instance, Peterson et al. (2000) note that narrow line Seyfert 1 galaxies (NLS1s) seem to have smaller SBH masses (by a factor 10) than regular Seyfert 1 galaxies with comparable continuum luminosity, indicating that they are accreting at higher rates and/or efficiencies.”
• What the Optical Recombination Lines Can Tell Us about the Broad-Line Regions of Active Galactic Nuclei (2004, result): “…effect may have played a role in the observation of a large increase in the He ii k4686 equivalent width in comparison to H during a large increase in the continuum luminosity in NGC 5548 (Peterson & Ferland 1986) and likewise in a similar event reported by Peterson et al. (2000) in NGC 4051.”
• A light bending model for the X-ray temporal and spectral properties of accreting black holes (2003, background): “Peterson et al (2000) have argued that the optical lines in NGC 4051 can be explained by the broadline region (BLR) being flattened and viewed at low/moderateinclination.”
• REVERBERATION MAPPING MEASUREMENTS OF BLACK HOLE MASSES IN SIX LOCAL SEYFERT GALAXIES (2010, background): “However, the main conclusion of that comparison is that the light curves from which previous measurements of the lag were made (e.g., Peterson et al. 2000) were undersampled, leading to an overestimate of the lag.”
• What controls the C iv line profile in active galactic nuclei (2004, background): “…either be a pure viewing aspect effect in objects which are otherwise intrinsically similar (e.g. Richards et al. 2002), or it could be related to intrinsic differences in the dynamics of the high ionization component (Baldwin et al. 1996; Laor et al. 1997a; Peterson et al. 2000; Leighly 2004a).”
• 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.”
• Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation-Mapping Database (2004, result): “This object was also studied recently by Shemmer et al. (2003), who obtain a black hole mass consistent with the results of Peterson et al. (2000), who present the data we have used here.”
• The Compact, Conical, Accretion-Disk Warm Absorber of the Seyfert 1 Galaxy NGC 4051 and Its Implications for IGM-Galaxy Feedback Processes (2007, background): “The size of the Hβ BELR in NGC 4051, from reverberation mapping is 5.9 l-d (Peterson et al. 2000).”
• QUANTIFYING QUASAR VARIABILITY AS PART OF A GENERAL APPROACH TO CLASSIFYING CONTINUOUSLY VARYING SOURCES (2009, background): “If we take the continuum light curves 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…”
• Combined long and short timescale X-ray variability of NGC 4051 with RXTE and XMM-Newton (2003, background): “…the S/N on our resulting PSDs, and to improve our understanding of other phenomena such as ‘low’ states (eg Guainazzi et al. 1998; Uttley et al. 1999), and of the relationship between the X-ray and optical flux variations (Peterson et al. 2000; Shemmer et al. 2003), we then increased our coverage.”
• A Reverberation-based Mass for the Central Black Hole in NGC 4151 (2006, background): “In fact, this relationship has been found in NGC 5548 (Peterson & Wandel 1999) as well as a handful of other objects (Peterson et al. 2000; Onken & Peterson 2002; Kollatschny 2003).”
• Determining Central Black Hole Masses in Distant Active Galaxies and Quasars. II. Improved Optical and UV Scaling Relationships (2002, methodology): “This is probably seen for He ii in NGC 4051 (Peterson et al. 2000).”
• Radio-loud Narrow-Line Type 1 Quasars (2006, background): “While the relation is now well established for nearby Seyfert galaxies, few NLS1s have been reverberation mapped so far (Peterson et al. 2000).”