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Iron and nickel abundances of subluminous O-stars. I. NLTE-model atmospheres with line blanketing by iron group elements.
Werner, K.; Dreizler, S.; Heber, U. +2 more
NLTE model atmospheres for hot evolved stars including line blanketing of all iron group elements were first constructed by Dreizler & Werner (1993). In this paper we improve computational details and check the adopted simplifications. We also present a systematic investigation of the consequences of iron group line blanketing on the atmospher…
The Environments of Supernovae in Archival Hubble Space Telescope Images
Filippenko, Alexei V.; Leibundgut, Bruno; Barth, Aaron J. +2 more
We have examined the immediate environments of several supernovae using archival prerefurbishment Hubble Space Telescope images to search for clues to the nature of the progenitor stars. For the Type II supernova 1968L in M83 the colors of nearby star clusters indicate ages of <~ 6-7 x 10^6^ yr, implying an initial mass of ~> 25-30 M_sun_ fo…
The mid-infrared color of NGC 6946.
Helou, G.; Lord, S. D.; Malhotra, S. +10 more
We analyze the new mid-infrared maps of NGC 6946 for variations in the color ratio of the 7-to-15µm emission. Our preliminary findings are that this mid-infrared color is remarkably constant between arms and inter-arm regions, and as a function of radius in the disk, excluding the nuclear region. As surface brightness ranges by more than an …
A Candidate Gravitational Lens in the Hubble Deep Field
Hogg, David W.; Fassnacht, C. D.; Blandford, Roger +2 more
The discovery of HDF J123652+621227, a candidate gravitational lens in the Hubble Deep Field, is reported. This lens may be multiply imaging several optical sources at different redshifts. If follow-up spectroscopy of the lens and the brightest image confirms this hypothesis, observations of this system alone can be used to obtain an estimate of t…
Spectroscopy of Bright Quasars with the Hubble Space Telescope and Lyman-Alpha Absorption Lines in the Redshift Range 0.5 < Z < 1.7
Malkan, M. A.; Impey, C. D.; Petry, C. E. +1 more
We report ultraviolet spectroscopy of three bright quasars obtained with the Faint Object Spectrograph of the Hubble Space Telescope. The good quality spectra covering the range 1800-3300 A result from spectropolarimetry acquired for these targets, the interpretation of which has been published elsewhere. Objective algorithms were used to select a…
Theoretical amplitudes of solar g-modes.
Andersen, B. N.
This work presents predictions on the amplitudes of solar g-modes. It is based on the assumption that convective overshoot into the convectively stable interior generates gravity waves. Based on this assumption it is possible to estimate values for the amplitude of the g-modes below the solar convection zone. Numerical simulations, giving the tran…
Hubble Space Telescope Observations of the Seyfert Galaxy NGC 3783: Discovery of Variable C IV Absorption
Hutchings, John B.; Reichert, Gail A.; Mushotzky, Richard F. +5 more
We have discovered variable absorption lines in HST spectra of the Seyfert 1 galaxy NGC 3783. C IV λλ1548.2, 1550.8 absorption is present in an FOS spectrum on 1992 July 27 and a GHRS spectrum on 1994 January 16 at a radial velocity of -450 km s^-1^ relative to the emission-line peak, but there is no evidence for absorption in a GHRS spectrum on 1…
The regular structure of shock-accelerated ~40-100keV electrons in the high latitude heliosphere.
Simnett, G. M.; Tappin, S. J.; Roelof, E. C.
The passage of Ulysses through the high latitude heliosphere has given us a new insight into the interplanetary dynamical processes which are occurring, at any rate near solar minimum, in the heliosphere above the streamer belt. We report here observations of ~40-100keV electrons and ~0.5MeV protons detected by HI-SCALE from 1992-96. Apart from a …
Hubble Space Telescope/FOS Spectroscopy of VW Hydri in Superoutburst
Szkody, P.; Sion, E. M.; Huang, M. +2 more
We present an analysis of two HST/FOS UV spectra of the SU UMa type dwarf nova, VW Hyi, obtained on 1993 October 24, ∼5 days after the optical rise of a superoutburst The absorption features in the first spectrum appear to consist of two components: a broad-winged component (with velocity width of 3000 km s-1) and a sharp core narrow co…
The Masses and Radii of the Eclipsing Binary zeta Aurigae
Harper, Graham M.; Bennett, Philip D.; Brown, Alexander +1 more
We present a full determination of the fundamental stellar and orbital parameters of the eclipsing binary ζ Aurigae (K4 Ib + BS V) using recent observations with the Hubble Space Telescope Goddard High Resolution Spectrograph (GHRS) and the Mark III long-baseline optical interferometer. The information obtained from spectroscopic and interferometr…