Search Publications
Implications of the ionizing continuum of 3C 263.
Fabian, A. C.; Naylor, T.; George, I. M. +1 more
We present ultraviolet IUE and soft X-ray EXOSAT observations of the quasar 3C 263 which reveal the low-energy part of the ionizing continuum and allow the high-energy tail to be strongly constrained. The ionizing spectrum confirms that the pressure of the extra-nuclear emission-line gas discovered earlier by us around the quasar is greater than 1…
Carbon in Orion
Walter, D. K.
The carbon abundance in the Orion nebula is redetermined from a detailed study of UV spectra in the IUE archives. Temperature and electron density gradients were derived for the inner 5 arcmin of the nebula using new and existing observational data. These temperatures and densities were used to calculate the carbon abundance for 19 positions large…
IUE Observations of Early-Type Stars at High Galactic Latitudes
Dufton, P. L.; Keenan, F. P.; Brown, P. J. F. +2 more
High- and low-resolution IUE spectra of 14 apparently normal high-Galactic latitude B-type stars, together with visual fluxes determined from Stroemgren four-color photometry, are compared with theoretical spectra deduced from LTE model atmosphere calculations. Ten of the program stars have normal flux distributions, with only four of the stars ex…
A Non--Local Thermodynamic Equilibrium, Line-blanketed Synthetic Spectrum of IOTA Herculis: C, Al, and SI Lines
Grigsby, James A.
A non-LTE line-blanketed model stellar atmosphere is used to compute a model of I Herculis (B3 IV) with a Teff of 17,500 K and a log g of 3.75, following the conclusions of Peters and Polidan (1985). Detailed profiles of a number of lines of C, Al, and Si in the 1200-2000-A region are computed, including the resonance lines of C II, Al II, and Al …
Observations of X-ray spectra of two nearby QSO's : MRK 205 and MRK 1148.
Singh, K. P.; Rao, A. R.; Vahia, M. N.
The 0.1 - 10 keY X-ray spectra of two nearby quasistellar objects (QSO's) known as Markarian 205 (Mrk 205) and Mrk 1148 (PG 0049+171), are presented based on observations with the EXOSAT Observatory. Simple power law models with the line of sight absorption consistent with the values obtained from the 21 cm surveys are sufficient to explain the ob…
First Results from the Faint Object Camera: High-Resolution Imaging of the Pluto-Charon System
Boksenberg, A.; Barbieri, C.; Weigelt, G. +16 more
The first observations of a solar system target with the Faint Object Camera of the HST are reported. Observations of the Pluto-Charon system were obtained in f/96 and f/288 mode. Pluto and Charon were clearly resolved, and the observed separation and diameters are in accordance with expectations. The f/96 data were astrometrically and photometric…
First Results from the Goddard High-Resolution Spectrograph: A Demonstration of Spectral Resolution and Experiments with Deconvolution
Ebbets, Dennis C.; Shore, Steven N.; Gilliland, Ronald L. +3 more
High-quality spectra of the sharp-lined star Chi Lupi were obtained with the Goddard High Resolution Spectrograph (GHRS). Spectra for the various resolving powers achievable with the echelle and G160M gratings are displayed. The effect of spherical aberration upon the spectral resolution is found to be negligible when using the small science apert…
Rotationalmodulation and flares on RS Canum Venaticorum and BY Draconis stars. XVI. IUE spectroscopy and VLA observations of GL 182 (=V 1005 Orionis) in October 1983.
Doyle, J. G.; Linsky, J. L.; Mathioudakis, M. +7 more
A large flare was detected simultaneously with IUE and VLA on Gl 182 on October 5, 1983, this event showing the largest C IV flare enhancement yet observed by IUE. A smaller flare was also detected on October 4, although only with the IUE satellite. Line ratio and emission measure techniques are used to derive various physical parameters of the fl…
X-Ray to Infrared Observations of the AM Herculis System E1405-451 (V834 Centauri)
Maraschi, L.; Chiappetti, L.; Motch, C. +5 more
The Exosat satellite observed E1405 - 451 in the X-ray band in March 1984 during a high state; and simultaneous UV, optical, and IR coverage was obtained with IUE and from ESO telescopes. The low-energy X-ray curve exhibits a minimum at phase zero which is similar to the optical one, with some indication of temperature modulation with orbital phas…
On Spectra of X-Ray Bursters in the Expansion Phase
Lapidus, I. I.
Two alternative approaches to the theoretical description of spectra of X-ray bursters showing radial expansion near the light curve maximum are presented. The first one, using the LTE assumption, can be used to explain the noticeable soft excess which is present in corresponding Exosat observations. The second one is based on numerical calculatio…