Search Publications
The First Detection of Ionized Helium in the Local ISM: EUVE and IUE Spectroscopy of the Hot DA Dwarf GD 246
Bowyer, Stuart; Vennes, Stephane; Chayer, Pierre +4 more
We report observations of the extreme ultraviolet spectrum of the hot degenerate star GD 246 obtained with the EUVE. Our initial attempt at modeling the photospheric emission from the white dwarf reveals a relatively uncontaminated pure H spectrum in the range above 200 A, allowing a study of interstellar continuum absorption features in the line …
HST Imaging of Hydrogen-poor Ejecta in Abell 30 and Abell 78: Wind-blown Cometary Structures
Harrington, J. P.; Borkowski, Kazimierz J.; Tsvetanov, Zlatan +1 more
HST Faint Object Camera images of hydrogen-poor gas in the planetary nebulae A30 and A78 have revealed remarkable 'cometary' structures in the O III 5007-A forbidden line. Most of these cometary structures, consisting of compact (0.15-0.5 arcsec) knots with radial tails several arcsec in length, are located in an equatorial plane in both nebulae. …
Evaluation of Emission Mechanisms at omega P E Using ULYSSES Observations of Type III Bursts
Goldstein, M. L.; Stone, R. G.; Lengyel-Frey, D. +1 more
We present the first observational tests of existing theories for the generation of type III radio bursts emitting at the fundamental plasma frequency, ωpe. This study is based on local radio emission and in situ wave phenomena associated with four interplanetary type III radio bursts observed by the unified radio and plasma wave experi…
High-Energy Spectrum of Cygnus X-1 Revisited
Done, C.; Fabian, A. C.; Matt, G. +1 more
The X-ray spectrum of Cyg X-1 is probably produced by thermal Comptonization in an accretion disk corona. Photons reflected from the disk are also Comptonized, so the predicted reflection spectrum is dependent on the optical depth and temperature of the scattering medium. Thus, observations of reflection in the 2-20 keV energy range can constrain …
Interstellar MG II and C IV Absorption toward Markarian 205 by NGC 4319: an ``Optically Thick'' QSO Absorption System
Bowen, David V.; Blades, J. C.
We have used the Goddard High-Resolution Spectrograph aboard HST to detect interstellar Mg II and C IV absorption lines toward Mrk 205, a QSO whose sightline passes within 3 h^-1^ kpc of the foreground galaxy NGC 4319. Absorption is detected from both local Milky Way gas and from NGC 4319, making this the first observation of an isolated, low-reds…
Ultraviolet Line Diagnostics of Accretion Disk Winds in Cataclysmic Variables
Shlosman, Isaac; Vitello, Peter
The IUE data base is used to analyze the UV line shapes of the cataclysmic variables RW Sex, RW Tri, and V Sge. Observed lines are compared to synthetic line profiles computed using a model of rotating biconical winds from accretion disks. The wind model calculates the wind ionization structure self-consistently including photoionization from the …
A Cluster of Nascent Galaxies at Z = 2?
Dressler, Alan; Oemler, Augustus, Jr.; Gunn, James E. +1 more
On a 6 hr Wide Field Camera exposure with the Hubble Space Telescope of the rich cluster CL 0939+4713, we have identified an apparent cluster of ~30 faint, extended objects with magnitudes 22 < r < 25. The objects are typically 1" in size with bright central regions only a few tenths of an arcsecond in size, and are distributed over a region…
Scattered Light in the Echelle Modes of the Goddard High Resolution Spectrograph aboard the Hubble Space Telescope. II. Analysis of In-Flight Spectroscopic Observations
Ebbets, Dennis C.; Savage, Blair D.; Cardelli, Jason A.
We report on an analysis of observations made with the GHRS aboard the HST for the purpose of calibrating the effects of scattered light. The data were obtained during the first 2 years of flight operations as part of the Science Verification, Science Assessment Observations, and Guaranteed Time Observations programs. Both the general level of bac…
The Population of Massive Stars in R136 from Faint Object Camera Ultraviolet Observations
Leitherer, Claus; Nota, Antonella; de Marchi, Guido +2 more
New ultraviolet (λ ≃ 1300 Å, λ ≃ 3400 Å), HST Faint Object Camera observations have been used to derive the UV color-magnitude diagram (CMD) of R136. The main scientific goal is the study of the upper end of the stellar mass function at ultraviolet wavelengths where the color degeneracy encountered in visual CMDs is less severe.
The CMD has b…Detection of an Ultraviolet and Visible Counterpart of the NGC 6624 X-Ray Burster
Boksenberg, A.; Barbieri, C.; Weigelt, G. +18 more
We have detected, in images taken with the HST FOC, the UV and optical counterpart of the X-ray source 4U 1820-30 in the globular cluster NGC 6624. Astrometric measurements place this object 2 sigma from the X-ray position of 4U 1820-30. The source dominates a far-UV FOC image and has the same flux at 1400 A as was seen through the large IUE apert…