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Ultraviolet and Radio Observations of Milky Way Halo Gas
Savage, Blair D.; Lockman, Felix J.; Danly, Laura +1 more
Interstellar-absorption-line and 21-cm emission-line data for sight lines to 56 stars are combined in order to study the kinematics and spatial distribution of the gas that is at great distances from the Galactic plane. Measurements of the interstellar velocities and H I column densities from the 21-cm emission and Ly-alpha absorption are included…
Eclipse Studies of the Dwarf Nova HT Cassiopeiae. II. White Dwarf and Accretion Disk
Horne, Keith; Wood, Janet H.; Vennes, Stephane
The white dwarf and accretion disk in the dwarf nova HT Cas are investigated by means of the simultaneous UBVR light curve presented by Horne et al. (1991). A temperature of 14,000 +/- 1000 K and a distance of 125 +/- 8 pc for E(B - V) = 0.0 are found. A blackbody fit to the UBVR fluxes yields T(W) of 13,600 +/- 1000 K and D of 140 +/- 12 pc. Thes…
Search for Partial Systemic Lyman Edges in Nearby Quasars
Koratkar, A. P.; Bohlin, R. C.; Kinney, A. L.
The Lyman edge region (912 A) of quasars is thought to be formed by thermally emitting accretion disks and would be affected by broad-line region (BLR) clouds. The Lyman edge discontinuities in disk models are predicted both in absorption (<= 80%) and in emission (<= 30%). For BLR clouds, the predictions range from complete absorption at the…
The Origin of Broad Emission Lines in the Extragalactic Giant H II Region NGC 2363
Dufour, R. J.; McCall, Marshall L.; Roy, Jean-Rene +1 more
High signal-to-noise long-slit spectra have been obtained of the giant H II region NGC 2363 located in the dwarf SBm galaxy NGC 2366. A discovery of low-intensity broad spectral components (FWHM ~40 A or 2400 km s^-1^) in the bright nebular lines Hα, Hβ, and [O III) is reported. The broad spectral components are detected over a large spatial exten…
The Hot Plasma Environment at Jupiter: Ulysses Results
Simnett, G. M.; Pick, M.; Anderson, K. A. +10 more
Measurements of the hot plasma environment during the Ulysses flyby of Jupiter have revealed several new discoveries related to this large rotating astrophysical system. The Jovian magnetosphere was found by Ulysses to be very extended, with the day-side magnetopause located at ~105 Jupiter radii. The heavy ion (sulfur, oxygen, and sodium) populat…
Detection of Fundamental and Harmonic Type III Radio Emission and the Associated Langmuir Waves at the Source Region
Stone, R. G.; Fainberg, J.; Reiner, M. J.
Type III radio emission generated in the vicinity of the Ulysses spacecraft has been detected at both the fundamental and harmonic of the local plasma frequency. The observations represent the first clear evidence of locally generated type III radio emission. This local emission shows no evidence of frequency drift, exhibits a relatively short ris…
A spectacular mass-loss event of the central star of Longmore 4.
Rauch, T.; Werner, K.; Heber, U. +3 more
We report on a dramatic change in spectral type of the central star of the planetary nebula Longmore 4. Its 'low state' spectrum is that of a PG 1159 star, i.e., of an extremely hot hydrogen-deficient (pre-) white dwarf, whereas its 'high state' spectrum has to be classified as of early Wolf-Rayet type (WC2-3). The observed spectral change reveals…
The interstellar neutral-gas experiment on ULYSSES.
Keppler, E.; Rosenbauer, H.; Witte, M. +5 more
The properties (density, bulk velocity relative to the solar system, and temperature) of the local interstellar gas, represented by neutral helium penetrating the heliosphere, will be measured in situ for the first time by the Ulysses Gas instrument. By employing the solar gravitational field as a natural velocity analyzer, the bulk velocity relat…
The Snapshot Survey: A Search for Gravitationally Lensed Quasars with the Hubble Space Telescope
Maoz, D.; Lahav, O.; Schneider, D. P. +4 more
In a systematic attempt to find new examples of multiply imaged quasars that are the result of gravitational lensing, 89 short exposures, through two filters, of high-luminosity quasars from a well-defined sample have been obtained with the Hubble Space Telecope's Planetary Camera. Useful high-resolution images of approximately 30 quasars have res…
Hubble Space Telescope Imaging of Distant Galaxies: 4C 41.17 at Z = 3.8
Chambers, K. C.; Macchetto, F.; Miley, G. K. +1 more
The Hubble Space telescope has been used to image the continuum emission from 4C 41.17 at z = 3.8, the most distant galaxy known. The galaxy was detected with good signal-to-noise ratio and was spatially resolved at the 0.1" (440 pc) HST resolution. The measured integrated flux density is in good agreement with the ground-based value (R~22). About…