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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…
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…
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…
The Optical Variability of PKS 2155-304
Miller, H. R.; Carini, Michael T.
The BL Lacertae object, PKS 2155 - 304, has been photometrically monitored for the past decade (1979-1990). Optical variations have been observed on time scales ranging from several minutes to several years. The variations detected with time scales on the order of minutes are among the fastest optical variations detected for a BL Lacertae object. …
Properties of the Massive X-Ray Binary 4U 1700-37 = HD 153919
Corcoran, M. F.; Heap, S. R.
The system parameters for the massive X-ray binary 4U 1700 - 37 are reexamined in the light of modern spectroscopic theory and new UV and X-ray data. The system is composed of HD 153919, an O6f star having a stronger wind, and an accreting neutron star. Revised parameters for the Of component are derived which are in accord with the parameters of …
CNO Abundances and Temperature Fluctuations in the Orion Nebula
Dufour, Reginald J.; Hester, J. J.; Walter, Donald K.
The largest UV-optical data base to date of the Orion Nebula has been assembled, and the CNO abundances their distribution at a statistically significant number of positions to the north and west of the Trapezium and out to a distance of 5 arcmin has been examined. The forbidden O III temperature increases with distance from Theta1 Ori C while the…
Observations of R Coronae Borealis Stars in Decline: Empirical Arguments for Dust Formation near the Stellar Surface
Stanford, S. A.; Clayton, Geoffrey C.; Drilling, John S. +1 more
We present new IUE observations which monitor the spectroscopic evolution of RY Sgr through a deep decline. These data, along with other IUE, visible, and infrared observations of declines in RY Sgr, R CrB, and V854 Cen, are considered in an attempt to understand the dust formation process and the source of the narrow- and broad-line emission seen…