Ultraviolet variability of NGC 5548 - Dynamics of the continuum production region and geometry of the broad-line region

Journal Article · Mon Apr 01 04:00:00 EST 1991 · Astrophysical Journal; (United States)

DOI:https://doi.org/10.1086/169918· OSTI ID:5540762

Krolik, J H; Horne, K; Kallman, T R; Malkan, M A; Edelson, R A ^[1]

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1. Johns Hopkins University, Baltimore, MD (USA) Space Telescope Science Institute, Baltimore, MD (USA) NASA, Goddard Space Flight Center, Greenbelt, MD (USA) California, University, Los Angeles (USA) Colorado, University, Boulder (USA)

Data from the 1989-1990 IUE monitoring of the Seyfert galaxy NGC 5548 are used here to analyze the continuum variability properties of the galaxy and to derive the structure or its emission-line region. The mean shape of the UV continuum is well fit by an accretion disk model with a given black hole mass and an additional component required to reproduce the observed soft X-ray flux. The continuum fluctuation power spectrum is very steep, with most of the variance coming from about 1 yr time scales. The entire optical/UV continuum rises and falls almost simultaneously, so that the logarithmic slope of the power spectrum is nearly the same for all bands, but the flux at higher photon frequencies varies with larger amplitude. The emission-line material around the nucleus may best be described by a highly ionized inner zone of high and nearly constant pressure that stretches about 4-14 light-days from the center and an outer, more weakly ionized zone of considerably lower ionization at least 20-30 light-days out. 44 refs.

• OSTI ID: 5540762
• Journal Information: Astrophysical Journal; (United States), Journal Name: Astrophysical Journal; (United States) Vol. 371; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCRETION DISKS
BLACK HOLES
ELECTROMAGNETIC RADIATION
EMISSION SPECTRA
FLUIDS
GALAXIES
GALAXY NUCLEI
GASES
IONIZED GASES
IONIZING RADIATIONS
MATHEMATICAL MODELS
MORPHOLOGY
RADIATIONS
SEYFERT GALAXIES
SOFT X RADIATION
SPECTRA
ULTRAVIOLET SPECTRA
VARIATIONS
X RADIATION