Search Publications
Faint Object Spectrograph Observations of the Low-Luminosity Seyfert Galaxy NGC 1566
Kriss, G. A.; Blair, William P.; Armus, L. +3 more
FOS observations of the Seyfert galaxy NGC 1566 show it to possess the broad lines characteristic of a typical Seyfert 1 galaxy, even in states of very low luminosity. The continuum, however, is steep (f_v_~v^- 1.5^) with no suggestion of the ultraviolet excess seen in higher luminosity AGNs. The broad emission lines have symmetric profiles, but a…
First Results from the Goddard High-Resolution Spectrograph: Element Abundances as a Function of Velocity in the Neutral Gas toward XI Persei
Ebbets, Dennis C.; Sembach, Kenneth R.; Savage, Blair D. +3 more
Observations of ultraviolet interstellar absorption lines toward Xi Persei obtained with the echelle mode of the Goddard High-Resolution Spectrograph (GHRS) aboard the HST at a resolution of 3.5 km/s are presented. The data for O I, C II, Mg II, S II, Fe II, Si II, Mn II, and Zn II are converted into representations of apparent column density per …
Evidence for a Thermally Unstable Shock Wave in the VELA Supernova Remnant
Raymond, John C.; Balick, Bruce; Wallerstein, George
The emission and absorption line signatures of supernova remnant shock waves provide complementary diagnostic capabilities. This paper presents IUE spectra of the nebulosity and new spectra of HD 72088. Models of the emission and absorption lines from shocked gas are used to derive a shock velocity and elemental depletions. There is evidence from …
Short-Term X-Ray Variability of the BL Lacertae Object PKS 2155-304: Power Spectrum and Cross-Correlation Analysis
Maraschi, L.; Tagliaferri, G.; Stella, L. +2 more
We present a detailed power spectrum and cross-correlation analysis of the X-ray light curves of the BL Lac object PKS 2155 - 304, obtained with EXOSAT. The power spectra show a marked red noise-type variability, with the power increasing steeply toward low frequency. The variability is more pronounced in the 1-6 keV band than in the 0.1-2 keV ban…
First Results from the Faint Object Camera: Imaging the Core of R Aquarii
Boksenberg, A.; Barbieri, C.; Weigelt, G. +16 more
The Faint Object Camera on the HST was pointed toward the symbiotic long-period M7e Mira variable R Aquarii, and very high resolution images of the inner core, mainly in the ionized oxygen emission lines in the optical, are reported. Both images show bright arcs, knots, and filaments superposed on a fainter, diffuse nebulosity extending in a gener…
Inefficient Accretion by the DA2 White Dwarf in V471 Tauri
Mullan, D. J.; Sion, E. M.; Shipman, H. L. +1 more
The results are reported of an analysis of eight-high-resolution International Ultraviolet Explorer (IUE) short-wavelength primary spectra of V471 Tauri, an eclipsing-spectroscopic, precataclysmic binary in the Hyades. The coaddition in velocity space of regions surrounding principle high- and low-excitation ion species on a common velocity scale …
High-Resolution IUE Spectra of the Nova-like Variable IX Velorum
Mauche, Christopher W.
The paper addresses two separate but related studies utilizing high-resolution ultraviolet spectra of the nova-like variable IX Velorum, obtained by the IUE satellite. The observations used in the studies are described, and the velocity offsets of the broad Si IV absorption features and the variability of the shapes of the P Cygni profiles of Si I…
Binary Star Observations with the Hubble Space Telescope Fine Guidance Sensors. I. ADS 11300
Benedict, G. F.; Franz, O. G.; Kreidl, T. J. N. +13 more
According to an orbit based on measures mostly near apastron, the binary ADS 11300 = Hu 581 = WDS 18229 + 1458 passed through periastron in 1984 at an angular separation below 0.1 arcsec. On the assumption that one accurate measurement near periastron may serve to define its orbit, ADS 11300 was selected for Early Release Observation (ERO) with th…
Densities and Abundances of Hot Cometary Ions in the Coma of P/Halley
Balsiger, H.; Ip, W. -H.; Goldstein, B. E. +3 more
The densities of the hot component in the ion population observed in the P/Halley coma by the ion mass spectrometer aboard the Giotto spacecraft has been recomputed, and the results are reported. Except for protons and H2(+), all densities are found to be at least an order of magnitude higher than predicted by the physicochemical model of Schmidt …
The Binary Feige 24: The Mass, Radius, and Gravitational Redshift of the DA White Dwarf
Thorstensen, John R.; Vennes, Stephane; Shipman, Harry L. +1 more
Observations are reported which refine the binary ephemeris of the Feige 24 system, which contains a peculiar hot DA white dwarf and an M dwarf with an atmosphere illuminated by extreme ultraviolet radiation from the white dwarf. With the new ephemeris and a set of IUE high-dispersion spectra, showing phase-dependent redshifted C IV, N V, and Si I…