Profile variability of the H-alpha and H-beta broad emission lines in NGC5548

Abstract

Between 1996 and 2002, we have carried out a spectral monitoring program for the Seyfert galaxy NGC 5548. High quality spectra (S/N>50), covering the spectral range (4000-7500)AA were obtained with the 6 m and 1 m telescopes of SAO (Russia) and with the 2.1 m telescope GHO (Mexico). We found that both the flux in the lines and the continuum gradually decreased, reaching minimum values during May-June 2002. The mean, rms, and the averaged over years, observed and difference line profiles of H-alpha and H-beta reveal the double peaked structure at the radial velocity ~+-1000km/s. The relative intensity of these peaks changes with time. During 1996, the red peak was the brightest, while in 1998 - 2002, the blue peak became the brighter one. In 2000-2002 a distinct third peak appeared in the red wing of H-alpha and H-beta line profiles. The radial velocity of this feature decreased between 2000 and 2002 from ~+2500 km/s to ~+2000 km/s. The fluxes of the various parts of the line profiles are well correlated with each other and also with the continuum flux. Shape changes of the different parts of the broad line are not correlated with continuum variations and, apparently, are not related to reverberation effects. Changes of the integral Balmer decrement are, on average, anticorrelated with the continuum flux variations. This is probably due to an increasing role of collisional excitation as the ionizing flux decreases. Our results favor the formation of the broad Balmer lines in a turbulent accretion disc with large and moving "optically thick" inhomogeneities, capable of reprocessing the central source continuum.

arXiv commentAccepted for publication in A&A; 24 pages, 14 postscript figures

References in corpus (7)

• Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei: I. Comparing the Photoionization and Reverberation Techniques
• Jet directions in Seyfert galaxies
• Steps Toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XVI. A Thirteen-Year Study of Spectral Variability in NGC 5548
• Evolution of the Nuclear Accretion Disk Emission in NGC 1097: Getting Closer to the Black Hole
• Rejection of the Binary Broad-Line Region Interpretation of Double-Peaked Emission Lines in Three Active Galactic Nuclei
• Steps Toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XV. Long-Term Optical Monitoring of NGC 5548
• A Spectroscopic and Photometric Study of Short-Timescale Variability in NGC5548

Cited by in corpus (51)

• Systematic Effects in Measurement of Black Hole Masses by Emission-Line Reverberation of Active Galactic Nuclei: Eddington Ratio and Inclination
• The origin of the Broad Line Region in Active Galactic Nuclei
• Broad-line Balmer Decrements in Blue Active Galactic Nuclei
• AGN Type-casting: Mrk 590 No Longer Fits the Role
• The Lick AGN Monitoring Project: Recalibrating Single-Epoch Virial Black Hole Mass Estimates
• Spectroscopic Indication for a Centi-parsec Supermassive Black Hole Binary in the Galactic Center of NGC 5548
• A Bayesian Approach to Estimate the Size and Structure of the Broad-line Region in Active Galactic Nuclei Using Reverberation Mapping Data
• Spectral Optical Monitoring of the Narrow Line Seyfert 1 galaxy Ark 564
• Constraining Sub-Parsec Binary Supermassive Black Holes in Quasars with Multi-Epoch Spectroscopy. II. The Population with Kinematically Offset Broad Balmer Emission Lines
• Evidence for periodicity in 43 year-long monitoring of NGC 5548
• Long-term variability of the optical spectra of NGC 4151: I. Light curves and flux correlations
• Are there reliable methods to estimate the nuclear orientation of Seyfert galaxies?
• Long-term optical spectral monitoring of a changing-look AGN NGC 3516 I: Continuum and broad-line flux variability
• Constraints on the black hole spin in the quasar SDSS J094533.99+100950.1
• Spectral optical monitoring of 3C390.3 in 1995-2007: I. Light curves and flux variation of the continuum and broad lines
• Contribution of a Disk Component to Single Peaked Broad Lines of Active Galactic Nuclei
• Searching for Binary Supermassive Black Holes via Variable Broad Emission Line Shifts: Low Binary Fraction
• Partial dust obscuration in active galactic nuclei as a cause of broad-line profile and lag variability, and apparent accretion disc inhomogeneities
• Consistency of the black hole mass determination in AGN from the reverberation and the X-ray excess variance method
• Spectral optical monitoring of 3C 390.3 in 1995-2007: II. Variability of the spectral line parameters
• Rimmed and Rippled Accretion Disc Models to Explain AGN Continuum Lags
• Emission Signatures from Sub-parsec Binary Supermassive Black Holes II: Effect of Accretion Disk Wind on Broad Emission Lines
• The analysis of the hydrogen broad Balmer line ratios: possible implications to the physical properties of the BLR of AGN
• First long-term optical spectro-photometric monitoring of a binary black hole candidate E1821+643: I. Variability of spectral lines and continuum
• The post-maximum behaviour of the changing-look Seyfert galaxy NGC 1566
• Investigating Changing-Look Active Galactic Nuclei with Long-term Optical and X-Ray Observations
• The intrinsic Baldwin effect in broad Balmer lines of six long-term monitored AGNs
• Progenitor, environment, and modelling of the interacting transient, AT 2016jbu (Gaia16cfr)
• Time Series Analysis of Active Galactic Nuclei: The case of Arp 102B, 3C 390.3, NGC 5548 and NGC 4051
• Long-term monitoring of the broad-line region properties in a selected sample of AGN
• Long term variability of the Broad Emission Line profiles in AGN
• Estimating reddening of the continuum and broad-line region of active galactic nuclei: the mean reddening of NGC 5548 and the size of the accretion disc
• Long-term optical spectral monitoring of a changing-look active galactic nucleus NGC 3516 -- II. Broad-line profile variability
• On possible proxies of AGN light curves cadence selection in future time domain surveys
• Reverberation Mapping of PG 0934+013 with the Southern African Large Telescope
• Broad-line region in active galactic nuclei: Dusty or dustless?
• X-ray Absorption and Optical Extinction in the Partially Obscured Seyfert Nucleus in Mrk 1393
• Correlation between Line Width and Line Flux of Double-Peaked Broad Halpha of 3C390.3
• Changing looks of the nucleus of the Seyfert galaxy NGC 1566 compared with other changing-look AGNs
• SALT long-slit spectroscopy of HE 0435-4312: fast displacement in the Mg II emission line
• Taming the derivative: diagnostics of the continuum and H$\beta$ emission in a prototypical Population B active galaxy
• Velocity-Resolved Ionization Mapping of Broad Line Region. I. Insights into Diverse Geometry and Kinematics
• Application of the FRADO model of BLR formation to the Seyfert galaxy NGC 5548 and the first step toward determining the Hubble constant
• Viscous torque in turbulent magnetized AGN accretion disks and its effects on EMRI's gravitational waves
• Line shape variability in a sample of AGN with broad lines
• Differential interferometry of close binary of supermassive black holes in an elliptical configuration
• Detection of an Unidentified Soft X-ray Emission Feature in NGC 5548
• The Broad Line Region of AGN: Kinematics and Physics
• Small telescopes being effective: MAGIC or not?
• The broad emission line asymmetry in low mass ratio of supermassive binary black holes on elliptical orbits
• On the time delay evolution of five Active Galactic Nuclei