Emission-line variability and the broad-line region of quasi-stellar objects. I. Time scales and photon densities

Journal Article · Sun Nov 01 04:00:00 EST 1987 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/165712· OSTI ID:5425519

Zheng, W; Burbridge, E M; Smith, H E; Cohen, R D; Bradley, S E

Spectroscopic data for five low-redshift QSOs taken over several years are presented as evidence for emission-line variability in QSOs. The broad hydrogen emission lines in the QSOs 0026 + 129, 1202 + 281, 1612 + 261, and 2141 + 175 are found to vary in step with their underlying continua. Another QSO, 2135 - 147, shows an increase in the intensities of its hydrogen lines five years after the increase in its continuum level. The inferred upper limit to the size of the broad emission line region is smaller than 3 lt-yr, probably as small as 0.4 lt-yr for 0026 + 129, if the line-emitting region is spherically distributed. Such a small size implies a very high density of ionizing photons, of the order of 10 to the 10th/cu cm. A very high nucleon density must then be assumed in order to obtain a value of the ionization parameter consistent with current photoionization models. 40 references.

• Research Organization: California Univ., La Jolla (USA)
• OSTI ID: 5425519
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 322; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC RADIO SOURCES
ELEMENTARY PARTICLES
EMISSION SPECTRA
IONIZATION
LINE WIDTHS
MASSLESS PARTICLES
MATHEMATICAL MODELS
PHOTOIONIZATION
PHOTONS
QUASARS
RED SHIFT
SPECTRA
VARIATIONS
WAVELENGTHS