Search Publications
IUE Observations of Accretion Columns in Two Zeta Aurigae--Type Systems
Ahmad, I. A.
This paper reports the existence of an accretion column in 32 Cyg. It also confirms the presence of the accretion column in ζ Aur and reports the detection of secular variations. Mg II observations support the parameters derived by Ahmad, Chapman, and Kondo for ζ Aur but suggest that the column may be curved. A C IV and Si IV emission component is…
Ultraviolet Survey for Hot Companions among Nonvariable Yellow Supergiants
Arellano Ferro, A.; Madore, B. F.
Twenty nonvariable yellow supergiants have been observed for the first time with the International Ultraviolet Explorer satellite, with the aim of discovering hot companions. Two newly discovered systems are announced: HD 74395 (G2 I + B9.5 IV-V) and HD 193469 (later than G0 + B8 IV-V). The Cepheid HD 9250 was also observed, but no hot companion w…
Rapid X-Ray and Optical Variability in the X-Ray--selected BL Lacertae Object 1E 1402.3+0416
Giommi, Paolo; Barr, Paul; Gioia, Isabella M. +4 more
Results from X-ray and optical observations of the X-ray-discovered BL Lac object 1E 1402.3 + 0416 are presented, where the X-ray measurements were carried out with the Channel Multiplier Array (CMA) and Medium Energy experiment (ME) detectors on board Exosat. These measurements revealed an intensity decrease by a factor of two on a time scale of …
The Unusual Ultraviolet Variability of the QSO 3C 232
Kafatos, M.; Bruhweiler, F. C.; Sofia, U. J.
After examining ultraviolet IUE spectra of 18 QSOs with z greater than 0.35, it is found that one object, 3C 232 (z = 0.533), stands out as exhibiting higly unusual spectral and continuum variability. The H I-Ly-alpha shows at a factor of two decrease in a day. The magnitude of the UV continuum variability is reminiscent of that seen in the optica…
On the X-Ray and Ultraviolet Spectrum of the High-Redshift Quasar 3C 446
Tagliaferri, G.; Garilli, B.
Existing IUE and Einstein observations of the high-redshift (z = 1.414) quasar 3C 446 have been analyzed. In the UV the continuum is characterized by a steep slope. The lack of signal shortward of 2300 Å is probably due to the Lyman continuum absorption at the source. The X-ray spectrum shows the "universal" slope of active galactic nuclei coupled…
Colors of Reflection Nebulae. III. Ultraviolet Scattering by Small Particles in Reflection Nebulae Associated with 17, 20, and 23 Tauri
Bohlin, R. C.; Witt, A. N.; Stecher, T. P.
New surface brightness measurements in the reflection nebulae associated with the Pleiades stars 17, 20, and 23 Tau have been carried out with the IUE satellite. Each nebula was observed at two angular offsets south of the respective illuminating star. At the larger offsets (40, 40, and 60 arcsec respectively) each nebula exhibits a flux distribut…
EXOSAT and Einstein X-Ray Observations of the SNR 1E 1149.4-6209 in Crux: A Unified Picture?
Caraveo, P. A.; Bignami, G. F.; Mereghetti, S. +2 more
New EXOSAT and Einstein Observatory X-ray data from a region in Crux (α ≈ 11h45m, δ ≈ 62°) are reported. Morphological as well as rough spectral analysis of a large (≡1°) diffuse feature is performed. The diffuse emission is identified with a SNR, a conclusion supported by comparison with existing radio and optical data. The …
Far-Ultraviolet and Optical Spectrophotometry of X-Ray Selected Seyfert Galaxies
Grewing, M.; Bowyer, S.; Clarke, J. T.
Five X-ray selected Seyfert galaxies were examined via near-simultaneous far-ultraviolet and optical spectrophotometry in an effort to test models for excitation of emission lines by X-ray and ultraviolet continuum photoionization. The observed Ly-alpha/H-beta ratio in the present sample averages 22, with an increase found toward the high-velocity…
The Extinction Law in the Open Cluster NGC 457 and the Intrinsic Energy Distribution of phi Cassiopeiae (F0 Ia)
Morrison, N. D.; Rosenzweig, P.
Five early B-type stars near the main-sequence turnoff in NGC 457 have been observed at low dispersion with the short-wavelength prime and the long-wavelength redundant cameras of the IUE satellite. The equivalent widths of spectral features that are particularly strong and sensitive to temperature and luminosity were computed in the cluster stars…
The Orbit and Properties of the HD 149162 System
Mayor, M.; Johnson, Hugh M.
HD 149162 is classified photometrically single and SB1 except for H-alpha emission that departs widely from the radial velocity of the K0 dwarf. Ca II H and K and Mg II h and k also show emission components at low dispersion. The system is X-ray luminous although ostensibly old disk and a slow K dwarf rotator. The orbit and other observations lead…