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Electron Density Diagnostics for Gaseous Nebulae Involving the O IV Intercombination Lines near 1400 Angstrom
Feibelman, W. A.; Keenan, F. P.; Conlon, E. S. +2 more
The Bloom and Pradhan (1992) results on the excitation rates for transitions in O IV matrix are used to derive emission-line ratios near 1400 A, applicable to gaseous nebulae. The results are compared with the values measured from high-resolution spectra obtained by the IUE satellite.
Variability and emission mechanism in Seyfert 1 galaxies : a near-infrared outburst in NGC 4051.
Hunt, L. K.; Del Zanna, G.; Wamsteker, W. +6 more
In the course of a 2.2 micron monitoring programme of nearby Seyfert 1 galaxies, we have detected an outburst in NGC 4051 in which the source flared and dimmed by more than a factor of 2 in 6 months. The UV flux, although sparsely sampled, is less variable than the near infrared. The available data suggest that dust reprocessing of the UV radiatio…
A New Look at the Dust Toward Omicron Persei and Sigma Scorpii With the International Ultraviolet Explorer
Clayton, Geoffrey C.; Hanson, Margaret M.
The first IUE low dispersion spectra for Omicron Persei and Sigma Scorpii have been obtained and extinction curves from 1150 to 3250 A are presented. It is of interest to consider Omicron Persei and Sigma Scorpii dust in the context of the average extinction law of Cardelli et al (1989), here referred to as 'CCM', which depends on the R(v) paramet…
Giotto's second encounter: The mission to comet P/Grigg-Skjellerup
Schwehm, G.; Grensemann, M. G.
The second highlight in the life of the Giotto spacecraft, which was originally designed for a short 8-month lifetime, occurred on 10 July 1992. The main mission was to explore and photograph Halley's Comet; however, not only did Giotto survive the harsh environment around the comet Halley but is was also able, after more than 7 years in orbit aro…
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…
Ordinary and Z-mode emissions from the Jovian polar region
MacDowall, R. J.; Kaiser, M. L.; Desch, M. D. +2 more
The Ulysses Unified Radio and Plasma (URAP) experiment has detected a new component of Jupiter's radio spectrum in the frequency range from about 10 to 30 kHz. This component is emitted in the magnetoionic ordinary mode from a localized corotating source in the northern polar region. The source is centered at system III longitude 208°, near the me…
Ultraviolet Properties of Individual Hot Stars in Globular Cluster Cores. I. NGC 1904 (M79)
Altner, B.; Matilsky, T. A.
As part of an observing program using the IUE satellite to investigate the properties of stars within the cores of Galactic globular clusters, we have obtained three spectra of the cluster NGC 1904 (M79). All three were long-integration-time, short-wavelength (SWP) spectra obtained at the so-called 'center-of-light', and all three showed evidence …
ROSAT-pointed observations of two gamma-ray burst error boxes.
Hurley, K.; Motch, C.; Kouveliotou, C. +3 more
We present ROSAT observations of two gamma-ray burst error boxes and of one possible optical transient source. No point sources were detected and a comparison is made with previous observations of the same objects (Boer et al. 1988, 1991). We interpret the data in the context of gamma-ray burst models that invoke galactic neutron stars. Although r…
Luminosities for Two Yellow Supergiants: Non-variables and the Instability Strip
Evans, Nancy R.
The luminosities for two yellow supergiants HD 183864 and Psi And = HD 223047 are determined from the IUE spectra of their hot companions. The absolute magnitudes of HD 183864 and HD 223047 are -2.3 and -2.1 mag, respectively, and their companions have spectral types of A0.0 V and B8.8 V. The companion of Psi And is compatible with the orbital mot…
Sulfur abundances in the solar wind measured by SWICS on Ulysses
Geiss, J.; Galvin, A. B.; Ipavich, F. M. +4 more
One of the nine experiments on Ulysses (launched October, 1990), the Solar Wind Ion Composition Spectrometer, utilizes an energy per charge deflection system along with time of flight technology to uniquely determine the mass and mass per charge of solar wind particles. Thus the composition of various solar wind types can be analyzed. Using the SW…