Ultraviolet and optical variations in active galactic nuclei - The Seyfert 1 galaxy NGC 5548

Journal Article · Tue May 01 04:00:00 EDT 1990 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/168707· OSTI ID:6710081

Wamsteker, W; Rodriguez-Pascual, P; Wills, B J; Wills, D; Netzer, H ^[1]

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1. IUE Observatory, Madrid (Spain) Madrid Universidad Complutense (Spain) Texas Univ., Austin (USA) Wise Observatory (Israel)

The results of an extensive coordinated UV and optical spectroscopic study of the Seyfert 1 galaxy NGC 5548 are presented. The very broad component has a blueshift of 2000 km/s, possibly indicating obscuration in the innermost parts of an accretion disk. Unlike Ly-alpha, the very broad C IV 1549 A does not continue to increase with the UV continuum at large flux levels. For the broad component, the ratio semiforbidden C III 1909 A/C IV 1549 A is independent of the continuum luminosity, suggesting a large ionization parameter. The Balmer decrement in the broad component is smaller when the continuum is brighter. Ly-alpha and H-gamma increase more than H-alpha and H-beta with increasing UV flux. The He II lines are very broad and change by a factor of up to four. They seem to react quickly to UV continuum changes, and there is no need to invoke accretion events to explain their variability. 67 refs.

• OSTI ID: 6710081
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 354; 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
BALMER LINES
DOPPLER EFFECT
ELEMENTS
EMISSION SPECTRA
GALAXIES
GALAXY NUCLEI
HYDROGEN
IONIZATION
LYMAN LINES
NONMETALS
PHOTOMETRY
SEYFERT GALAXIES
SPECTRA
ULTRAVIOLET SPECTRA
VARIATIONS
VISIBLE SPECTRA