Search Publications
Fitting Improved Accretion Disk Models to the Multiwavelength Continua of Quasars and Active Galactic Nuclei
Malkan, Matthew A.; Sun, Wei-Hsin
We present fits to the ultraviolet-optical-infrared spectra of 60 quasars and active galactic nuclei (AGNs) using improved black hole accretion disk models. The disk is assumed geometrically thin and optically thick. We included the relativistic effects of disk inclination, including Doppler boosting, gravitational focusing, and gravitational reds…
Kinematic Evidence for a Relativistic Keplerian Disk: ARP 102B
Filippenko, Alexei V.; Halpern, Jules P.; Chen, Kaiyou
The broad emission lines of the elliptical galaxy Arp 102B have peaks which are significantly displaced in velocity with respect to the host galaxy of the active galactic nucleus (AGN). We calculated line profiles for a Keplerian disk, including relativistic effects which were not treated rigorously in previous papers. We found an excellent fit of…
Hot Dust on the Outskirts of the Broad-Line Region in Fairall 9
Glass, I. S.; Clavel, J.; Wamsteker, W.
Since 1978, the Seyfert 1 galaxy F9 has been observed 54 times in the far-ultraviolet and optical (FES) range with the IUE, and at 27 different epochs at J, H, K, and L. The UV continuum underwent dramatic variations, its intensity decreasing by a factor 33, from a maximum in 1978 to a deep minimum in mid-1984. The near-IR and optical fluxes chang…
Narrow Ultraviolet Emission Lines from SN 1987A: Evidence for CNO Processing in the Progenitor
Panagia, N.; Fransson, C.; Kirshner, R. P. +4 more
UV observations of SN 1987A with the IUE satellite are reported. Spectra after 1987 May 24 show emission lines of He II, C III, N III, N IV, N V, and O III, increasing in strength with time. High-resolution observations show that the widths of the lines are less than ~30 km s^-1^ (FWHM). The line strengths and widths indicate an origin in a photoi…
The Evolution of Chromospheric Activity of Cool Giant and Subgiant Stars
Drake, Stephen A.; Simon, Theodore
IUE spectra for a large sample of cool subgiant stars are examined, and evidence is found that subgiants in the mass range 1.2-1.6 solar masses undergo a sudden decline in UV transition region emission near B - V = 0.6, which corresponds to spectral type G0 IV. The decline in UV emission coincides with a sharp decrease in stellar rotation rates, a…
The Infrared Emission Bands. III. Southern IRAS Sources
Tielens, A. G. G. M.; Allamandola, L. J.; Cohen, Martin +5 more
Airborne 5-8-micron spectra of southern IRAS sources are presented which display the strong PAH emission features. The sources studied include those in a previous paper (Cohen et al, 1986) and NGC 6302, HR 4049, and CPD -56 deg 8032. A good correlation is found between the intensity ratio of the 7.7-micron feature relative to the FIR dust continuu…
Pre--Main-Sequence Disk Accretion in Z Canis Majoris
Kenyon, S. J.; Stauffer, J. R.; Edwards, S. +4 more
It is suggested that the pre-main-sequence object Z CMa is a luminous accretion disk, similar in many respects to the FU Orionis variables. Z CMa shows the broad, doubled optical absorption lines expected from a rapidly rotating accretion disk. The first overtone CO absorption detected in Z CMa is blue-shifted, suggesting line formation in a disk …
The Kinematics of Milky Way Halo Gas. I. Observations of Low-Ionization Species
Danly, Laura
Ultraviolet interstellar line day observed with the IUE toward 70 halo stars and four extragalactic sight lines are analyzed in a study of the large-scale kinematic properties of the Milky Way halo gas. The motions of the low-ionization gas is focused on. Large systematic velocities are found, and a pronounced asymmetry in the absorption character…
Emission-Line Variability of Fairall 9: Determination of the Size of the Broad-Line Region and the Direction of Gas Motion
Koratkar, Anuradha P.; Gaskell, C. Martin
A cross-correlation analysis has been performed on 118 IUE spectra of Fairall 9 available from 1978 to January 1987 to determine the size of the broad-line region and the average direction of gas motion. Analysis of the line flux shows that the C IV λ1549 emitting region is 124 +/- 39 light days from the central source and the Mg II λ2800 emitting…
UV Fluorescence of Molecular Hydrogen and Red Dust Emission in the Gamma Cassiopeiae Nebulae IC 63
Bohlin, Ralph C.; Witt, Adolf N.; Stecher, Theodore P. +1 more
Resonant fluorescence of molecular hydrogen has been observed in the reflection nebula IC 63 with the IUE satellite. Both the noncoherent resonant scattering and the dissociative continuum are shown to agree well with molecular theory. Extended red emission is also found in this nebula and may be physically related to the dissociation of H2.