Search Publications
The Ultraviolet Absorption Spectrum of the Quasar H1821+643 (z = 0.297)
Schneider, Donald P.; Green, Richard F.; Jannuzi, Buell T. +2 more
We report measurements of the absorption lines in the ultraviolet spectrum of the nearby luminous quasar H1821+643 (z = 0.297). The results were obtained using high-resolution observations with the faint object spectrograph of the Hubble Space Telescope. A total of 51 absorption lines and a number of emission features were detected between 1190 an…
The Constitution of the Atmospheric Layers and the Extreme Ultraviolet Spectrum of Hot Hydrogen-rich White Dwarfs
Vennes, Stephane
An analysis is presented of the atmospheric properties of hot, H-rich, DA white dwarfs that is based on optical, UV, and X-ray observations aimed at predicting detailed spectral properties of these stars in the range 80-800 A. The divergences between observations from a sample of 15 hot DA white dwarfs emitting in the EUV/soft X-ray range and pure…
The Hubble Space Telescope Observations of X-Ray Nova MUSCAE 1991 and Its Spectral Evolution
Panagia, N.; Horne, Keith; Shrader, C. R. +4 more
Hubble Space Telescope Faint Object Spectrograph (FOS) Faint Object Camera (FOC) and observations of Nova Muscae 1991 obtained on May 14-15, 1991 are presented and discussed. A nearly featureless continuum with broad 2200 A absorption feature and no Balmer jump is found. The FOS spectrum is modeled, including previous multiepoch IUE, optical, and …
Time Series Observations of O Stars. I. IUE Observations of Variability in the Stellar Wind of zeta Puppis
Howarth, I. D.; Bolton, C. T.; Prinja, R. K. +7 more
Stellar wind variability in Zeta Pup (O4 I(n)f) is described based on 31 high-resolution IUE observations secured over 5 1/2 days in 1989 April. Extensive changes are evident in the absorption regions of Si IV 1393.76, 1402.77A and N IV 1718.55A P Cygni profiles. Both lines exhibit similar patterns of variability, which are characterized by the de…
A Survey of Ultraviolet Variability in Blazars
Edelson, Rick
This is the first comprehensive consistent survey of the ultraviolet variability properties of a large sample of blazars. All of the 14 blazars with five or more observations in a single IUE, camera showed significant variability. The strength of the ultraviolet variability is positively correlated with both the apparent ultraviolet luminosity and…
An Interpretation of the Spectral Properties of Hot Hydrogen-rich White Dwarfs with Stratified H/He Model Atmospheres
Vennes, Stephane; Fontaine, Gilles
A grid of stratified H/He model atmospheres applicable to the interpretation of the spectral properties of hot H-rich white dwarfs (WDs) is computed. Samples of hot DA WDs observed with Exosat and Einstein are analyzed using the models. Six out of six objects with T(eff) = 35,000 K or less do not show a EUV/soft X-ray flux deficiency and therefore…
Rapid Oscillations in Cataclysmic Variables. VIII. YY Draconis (=3A 1148+719
Caillault, J. -P.; Schwartz, D. A.; Williams, G. A. +3 more
A 16th magnitude cataclysmic variable presumably a dwarf nova, was detected near one of the positions permitted for the hard (2-10 keV) X-ray source 3A 1148 + 719. The optical and UV spectra of YY Dra are fairly typical of cataclysmic variables, except that the TiO absorption bands of an M dwarf can be seen for greater than 5000 A. This shows that…
Lyman-Alpha Emission in Star-forming Galaxies: Low-Redshift Counterparts of Primeval Galaxies?
Calzetti, D.; Kinney, A. L.
We present UV plus optical spectra of three galaxies, Mrk 496, Mrk 357, Tol 1924-416, obtained by matching the size of the optical aperture with that of IUE. From the Hα/Hβ ratios, we estimate values of E(B - V)-extinction due to dust-for the two Markarian galaxies which are higher than those derived in previous works. We have used the new values …
The 0623+71 Bow Shock Nebula
Feibelman, W. A.; Hollis, J. M.; Wagner, R. M. +1 more
Deep radio continuum and deep narrow-band optical emission-line images showing the cataclysmic variable 0623 + 71 engulfed in a bow shock morphology are presented. The limb-brightened H-alpha, forbidden N II and 6 cm radio continuum emission regions define the global nebular morphology, extending to much greater spatial distances than the apex-con…
Detection of a Proton Beam during the Impulsive Phase of a Stellar Flare
Robinson, Richard D.; Shore, Steven N.; Woodgate, Bruce E. +2 more
A transient event consistent with the predicted temporal and spectral signatures of an energetic proton beam was detected in the impulsive phase of a small flare on the red dwarf star AU Microscopii. It consisted of a prominent increase in the flux in the red wing of Lyman-alpha near 1223 A, simultaneously with the peak of a flare observed in the …