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…
The Transient 42 Second X-Ray Pulsar EXO 2030+375. I. The Discovery and the Luminosity Dependence of the Pulse Period Variations
Stella, L.; Parmar, A. N.; White, N. E. +2 more
The discovery of a new transient X-ray pulsar, EXO 2030+375, that is associated with a Be star companion, is reported. The results of a series of EXOSAT observations, where the evolution of the pulsar's properties over two orders of magnitude in luminosity was monitored. The dependence of the change in pulsar period on luminosity is measured and c…
The Transient 42 Second X-Ray Pulsar EXO 2030+375. II. The Luminosity Dependence of the Pulse Profile
Stella, L.; Parmar, A. N.; White, N. E.
During an outburst from the transient, 42 s, X-ray pulsar EXO 2030+375, marked luminosity-dependent changes in pulsar profile were observed. At high luminosities the pulse profile consisted of a smooth asymmetric main pulse separated by about 180 deg in phase from a small interpulse. As the luminosity decreased by a factor of about 100, the relati…
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 …
Coronal Activity in F-, G-, and K-Type Stars. III. The Coronal Differential Emission Measure Distribution of Capella, sigma 2 Coronae Borealis, and Procyon
Mewe, R.; Schrijver, C. J.; Lemen, J. R. +1 more
EXOSAT soft X-ray spectra of three binary systems of cool stars are analyzed: Capella (G6 III + F9 III), Sigma-squared CrB (F8 V + G1 V), and Procyon (F5 IV-V + DF). The EXOSAT transmission grating spectrometer permits the study of individual spectral lines and line complexes between 10 and 200 A with approximately 3 A resolution. First it is demo…