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Spherically Symmetric, Expanding, Non--LTE Model Atmospheres for Novae during Their Early Stages
Hauschildt, P. H.; Starrfield, S.; Wehrse, R. +1 more
In the continuum and line-blanketed models presented here, nova atmospheres are characterized by a very slow decrease of density with increasing radius. This feature leads to very large geometrical extensions so that there are large temperature differences between the inner and outer parts of the line-forming regions. The theoretical spectra show …
The SN 1986G in Centaurus A.
Schmutz, W.; Danziger, J.; Heydari-Malayeri, M. +10 more
We present photometric and spectroscopic observations of SN 1986 G, spanning up to one year after the explosion. The overall photometric behavior of this SN Ia results rather normal. The maximum at B = 1245+/-0.05 was reached on May 11,1986, then the decline to the inflection point was relatively fast (β_B_ = 12.0 mag/100 d), but similar to other …
The solar X-ray/cosmic gamma-ray burst experiment aboard ULYSSES
Cline, T.; Hurley, K.; Sommer, M. +7 more
The scientific objectives of the Ulysses solar X-ray/cosmic gamma-ray burst experiment, and the unique features of the Ulysses mission which will help to achieve them are described. After a discussion of the special design constraints imposed by the mission, the sensor systems, consisting of two CsI scintillators and two Si surface barrier detecto…
A Multiwavelength Study of Nova QU Vulpeculae 1984
Williams, Robert E.; Truran, James W.; Ferland, Gary J. +6 more
We have combined ground-based optical and satellite ultraviolet spectrophotometric data to study the ejected shell of Nova Vulpecula 1984 No. 2 (QU Vul). Substantial uncertainties concerning the nature of the ionizing continuum, and the role played by density inhomogeneities, now exist. Because of these uncertainties, the chemical composition is d…
Energetic Charged-Particle Phenomena in the Jovian Magnetosphere: First Results from the Ulysses COSPIN Collaboration
Balogh, A.; Kunow, H.; Muller-Mellin, R. +16 more
The Ulysses spacecraft made the first exploration of the region of Jupiter's magnetosphere at high Jovigraphic latitudes (~37^circ south) on the dusk side and reached higher magnetic latitudes (~49^circ north) on the day side than any previous mission to Jupiter. The cosmic and solar particle investigations (COSPIN) instrumentation achieved a rema…
Fractionation of CO in the Diffuse Clouds toward zeta Ophiuchi
Federman, S. R.; Lambert, David L.; Cardelli, Jason A. +1 more
An analysis of CO A-X bands in diffuse clouds toward Zeta Ophiuchi is presented. The results provide isotopic ratios that constitute the strongest observational evidence for highly localized isotopic fractionation of CO in diffuse portions of an interstellar cloud. The value of the fractionation implies that selective photodissociation is the cont…
Ultraviolet, Optical, and Infrared Observations of the High-Latitude Molecular Cloud toward HD 210121
Welty, Daniel E.; Fowler, James R.
Low-resolution UV spectra of the B3 V star HD 210121, located behind the high-latitude molecular cloud DBB 80, yield an extinction curve exhibiting a far-UV rise that is among the steepest known. The apparently simple line of sight affords an excellent opportunity for investigating the absorption and emission characteristics of a single, isolated …
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…