Search Publications
Signal-to-Noise Ratios in IUE Low-Dispersion Spectra. II. Photometrically-Corrected Images
Ayres, Thomas R.
The character of detector noise is explored in photometrically-corrected images from the shortwavelength and longwavelength prime intensified vidicon cameras of the International Ultraviolet Explorer. A protocol is proposed for deriving realistic "noise models"--crucial to the application of Optimal extraction algorithms like that of Kinney, Bohli…
Rapid Mass-Loss Transients in VV Cephei
Stencel, Robert E.; Potter, Daniel E.; Bauer, Wendy H.
Biweekly ultraviolet observations of the red supergiant-hot dwarf binary, VV Cephei during 1991, obtained near third quadrature, have revealed the existence of short-term continuum variations. We infer these are superposed on an underlying emission-line spectrum. The viewing geometry of this long period system suggests we are seeing a process asso…
The Companion of the Classical Cepheid Z Lacertae
Evans, Nancy R.; Welch, Douglas L.
A deep IUE exposure of the Cepheid Z Lac from 1200 to 2000 A has been taken in order to search for light from the radial velocity companion. A faint signal of approximately 1.0 X 10^-14 ergs A^-1 sec^-1 cm^-2 has been detected in the dereddened spectrum. Because this is approximately the flux expected due to "camera artifacts," we consider that at…
Recent Results from the Hubble Space Telescope
Maran, Stephen P.; Kinney, Anne L.
A selection of recent findings from the Hubble Space Telescope (HST) are presented as a supplement to the earlier review by Kinney & Maran (1991). In stellar astrophysics, noteowrthy results include the first ultraviolet science from the High Speed Photometer, as well as spectroscopic studies of black hole and neutron star binaries and a flare…
The Ultraviolet Spectrum of the Planetary Nebula VY 2-2
Feibelman, Walter A.
New ultraviolet short-wavelength (SWP) IUE observations for the protoplanetary nebula Vy 2-2 were obtained in the low dispersion mode. An exposure of 400 minute duration reveals a weak stellar continuum and several definite emission lines as well as a number of absorption features. Emission features of C III], Si III], and [Ne III] are clearly obs…
The Companion of the 18d Classical Cepheid YZ CAR
Evans, Nancy R.; Butler, John
We have obtained a deep IUE spectrum of the 18d Cepheid YZ Car. Flux has been detected at the level of 1-2 X 10^-15 ergs cm^-2 A^-1 sec^-1 from 1200 to 200 A, which we identify as the companion in the binary system. Since this is at least partly a result of "camera artifacts" built up during a long exposure, this is an upper limit to the flux of t…
Focus History of the Hubble Space Telescope - Launch to May 1993
Burrows, C. J.; Hasan, H.; Schroeder, D. J.
Since the launch of the Hubble Space Telescope (HST) the secondary mirror of the telescope has been moved several times in order to collimate the telescope and also to define a position of best focus. In addition to these moves the focus position changes over time because of water desorption by the graphite epoxy in the metering truss. We report h…
Resolved Structure in M33 Supernova Remnants
Blair, William P.; Davidsen, Arthur F.
We present WF/PC narrow band [S II] lambda-6725 images of two M33 supernova remnants obtained with the Wide Field/Planetary Camera on the Hubble Space Telescope. Comparison of these images with ground-based CCD data indicates that HST has resolved the nebular structures into shells or partial shells, permitting improved measurements of the diamete…
Hubble Space Telescope Observations of the Center of Globular Cluster M15
Yanny, Brian
Images of the dense center of globular cluster M15 (NGC 7078) have been obtained with the Hubble Space Telescope in the V and I filters. Accurate photometry is possible in the very densest part of the cluster center with rms errors of <0.3 magnitudes for stars down to the main sequence turnoff. Evidence for radial segregation between horizontal…
IUE Observations of Highly Ionized Gas toward Distant Stars in the Milky Way
Sembach, Kenneth R.
Combined high-dispersion IUE spectra of interstellar Si IV, C, IV, and N V absorption along distnat lines toward early type stars in the Galactic disk and low halo are discussed. The highly ionized species have complex profiles and exhibit stronger absorption toward distant low latitude stars than toward high latitude stars. Absorption along low l…