Search Publications
Stellar-Wind Variability in IUE Spectra of 68 Cygni
Howarth, Ian D.; Smith, Keith C.
We construct an empirical noise model for fully processed high-resolution, short-wavelength IUE spectra which takes crude account of the spatial variations of the camera response as well as the ripple-correction factors. We use this model to examine the velocity range over which statistically significant variability can be detected in the UV P Cyg…
Broad NE VIII lambda 774 Emission from Quasars in the HST-FOS Snapshot Survey (ABSNAP)
Hamann, Fred; Tytler, David; Zuo, Lin
We discuss the strength and frequency of broad Ne VIII λ774 emission from quasars measured in the HST-FOS snapshot survey (Absnap). Five sources in the survey have suitable redshifts (0.86 <= z_em_ <= 1.31), signal-to-noise ratios and no Lyman limit absorptions. Three of the five sources have a strong broad emission line near 774 A (rest), a…
HD 93521, zeta Ophiuchi, and the Effects of Rapid Rotation on the Atmospheres and Winds of O9.5 V Stars
Massa, Derck
Both low- and high-resolution IUE spectra of the rapidly rotating 09.5 V stars HD 93521 and zeta Oph are used to develop a coherent picture of the effects of rapid rotation on the atmospheres and winds of late, main-sequence O stars. The observational consequences are by far the strongest on HD 93521, most likely because it is being viewed nearly …
N IV Emission Lines in the Ultraviolet Spectra of Gaseous Nebulae
Feibelman, W. A.; Keenan, F. P.; Berrington, K. A. +4 more
Theoretical electron density sensitive emission-line ratios, determined using electron impact excitation rates calculated with the R-matrix code, are presented for R = I(2s2 (1)S-2s2p 3P2)/I(2s2 (1)S-2s2p 3P1 = 1(1483 A)/I(1486 A) in N IV. These are found to be up to an order of magnitude different from …
Recent Changes in the IUE Spectrum of the Very Young Planetary Nebula He 3-1357 (=SAO 244567)
Feibelman, Walter A.
We obtained the first high-dispersion IUE spectrum, and an additional low-dispersion spectrum of the very young planetary nebula He 3-1357 and its central star SDAO 244567. In 1988, it showed a very strong C IV lambda-1549 P Cygni profile which diminished and has disappeared by 1994, but C IV absorptions are seen in a high-resolution spectrum. The…
Neutral Sulfur Emission from the Io Torus Measured with the Hopkins Ultraviolet Telescope
Blair, William P.; Feldman, Paul D.; Kriss, Gerard A. +5 more
During the Astro 1 mission in 1990 December, ultraviolet spectra of the Io plasma torus were obtained using the Hopkins Ultraviolet Telescope. These spectra cover a wavelength range of 830-1860 Å in first order and 415-930 Å in second order. Two separate observations were made. Observation 1, which nominally contained Io within the aperture, cente…
Outer Layers of a Carbon Star: The View from the Hubble Space Telescope
Brown, Alexander; Robinson, Richard D.; Linsky, Jeffrey L. +13 more
To advance our understanding of the relationship between stellar chromospheres and mass loss, which is a common property of carbon stars and other asymptotic giant branch stars, we have obtained ultraviolet spectra of the nearby N-type carbon star UU Aur using the Hubble Space Telescope (HST). In this paper we describe the HST observations, identi…
GHRS Observations of Mass-loaded Flows in Abell 78
Borkowski, Kazimierz J.; Tsvetanov, Zlatan; Harrington, J. Patrick
Spectroscopic observations of the central star of the planetary nebula Abell 78 were obtained with the Goddard High Resolution Spectrograph (GHRS) onboard the Hubble Space Telescope (HST) in the vicinity of the C IV lambda 1548.2, 1550.8 doublet. We find a series of narrow absorption features superposed on the broad, P Cygni stellar wind profile. …
Detection of Hot Gas in the Interstellar Medium
Jenkins, Edward B.; Cowie, Lennox L.; Huang, Jia-Sheng +1 more
We present data on the C IV, Si IV, and N V absorption lines in eight disk stars observed by HST (Hubble Space Telescope) with the GHRS (Goddard High Resolution Spectrograph) at intermediate resolution. C IV and Si IV absorption lines are detected in seven target stars, while N V lines are detected in four distant stars and one nearby star. By fit…
Satellites on Lyman Alpha Due to H-H and H-H + Collisions
Kielkopf, John F.; Allard, Nicole F.
We have experimentally observed satellites on Lyman- alpha arising from radiative collisions of excited atomic hydrogen with unexcited neutral hydrogen atoms or protons. The wavelength, relative intensity, and shape of features in the Lyman- alpha wing emitted by a laser-produced plasma in pure hydrogen agree with new theoretical calculations base…