Search Publications
The Ultraviolet and Optical Continuum Emission in Active Galactic Nuclei: The Status of Accretion Disks
Koratkar, Anuradha; Blaes, Omer
A fundamental component of models of active galactic nuclei (AGNs) is an accretion disk around a supermassive black hole. However, the nature of this accretion disk is not well understood, and current models do not provide a satisfactory explanation of the optical/UV continuum observed in AGNs. In this paper we review the substantial theoretical a…
Multiwavelength Superoutburst Observations of T Leonis
Szkody, Paula; Howell, Steve B.; Ciardi, David R. +5 more
We present results of simultaneous superoutburst observations in the X-ray, EUV, optical, and IR bands of the tremendous outburst amplitude dwarf novae T Leonis. Near peak luminosity, a single blackbody represents a good fit to T Leo's observed continuum in the EUV spectral region, yielding a boundary layer temperature of 71,000-97,000 K. Inclusio…
A Time-Series IUE Archival Study of the White Dwarf in the Ultrashort-Period Dwarf Nova WZ Sagittae
Sion, E. M.; Cheng, F. H.; Slevinsky, R. J. +2 more
The IUE archive offers a series of far-UV spectra of the ultrashort-period dwarf nova WZ Sge over a long time baseline and hence the opportunity to monitor the ongoing accretion, the cooling of the white dwarf, and temporal variations in the line spectra. We have carried out a quantitative analysis of these spectra including model atmosphere simul…
A Study of the Time-dependent Background and Continuum Flux Levels in IUE High-Dispersion SWP Images
Smith, Myron A.
The extraction of net spectral fluxes from echellogram images for the creation of the final International Ultraviolet Explorer (IUE) archive was accomplished by the processing system NEWSIPS computing a background surface from unilluminated pixels over a wide area of the image for any given echellogram order. Although this technique facilitates th…
Detection of O VII lambda1522 in IUE Spectra of Planetary Nebula Nuclei and Other Hot Stars
Feibelman, Walter A.
We present the first detection of O VII lambda1522 emission or absorption from archival IUE spectra in 14 planetary nebula nuclei and three PG 1159-type stars. The n=5-->6 transition of O VII was determined by Kruk & Werner and observed by them in the spectrum of the very hot PG 1159-type star H1504+65 from data obtained with the Hopkins Ul…
Intereclipse Spectroscopic Snapshot of epsilon Aurigae with the Hubble Space Telescope
Lambert, David L.; Sheffer, Yaron
A single-epoch low-resolution Goddard High Resolution Spectrograph spectrum of the eclipsing binary epsilon Aurigae was obtained while the secondary was orbiting toward eclipse by the primary. The spectrum as recorded between 1175 and 1461 Å is rich with emission and absorption lines which include stellar and interstellar components. The emission-…
Ultraviolet Evidence for a Binary Nucleus of the Planetary Nebula SH 2-71
Feibelman, Walter A.
Archival IUE spectra of the planetary nebula Sh 2-71 show a variable Mg II lambda2800 emission line superposed on a variable stellar continuum. The Mg II feature is thought to be excited in the chromosphere of the cooler component of a binary nucleus, although other causes are also plausible.