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UV spectroscopy of Z Chamaeleontis - I. Time-dependent dips in superoutburst.
Sonneborn, G.; Charles, P. A.; Hassall, B. J. M. +2 more
Extensive IUE observations of the dwarf nova Z Cha during the 1987 April superoutburst and IUE-Exosat observations during the 1985 July superoutburst are presented. The UV light curve shows two dips when folded on the orbital period. One dip, at orbital phase 0.8 becomes shallower as the superoutburst progresses and can be associated with decreasi…
The Ionizing Radiation Field of NGC 4388 and Its Relation to the Extranuclear Emission-Line Regions
Colina, Luis
New long-slit spectroscopic observations of NGC 4388 and the extranuclear emission line regions around it are used to investigate the characteristics of the ionizing source and the structure of the extended emission-line regions. The measured luminosity of the [Fe VII) λ6087 emission line detected in the nucleus of NGC 4388 is interpreted as evide…
CPC2 - the Second Cape Photographic Catalog - Part Two - Conventional Plate Adjustment and Catalog Construction
Zacharias, N.; de Vegt, C.; Nicholson, W. +1 more
The Second Cape Photographic Catalog CPC 2, containing positions and visual magnitudes of 276 t 31 stars in the approximate magnitude range V= 6.5-10.5 is the first modern photographic catalog project on the southern hemisphere with an optimal fourfold plate overlap pattern and an astrometrically optimized spectral bandpass in the yellow - red reg…
Solar wind thermal electrons in the ecliptic plane between 1 and 4 AU: Preliminary results from the Ulysses radio receiver
MacDowall, R. J.; Bougeret, J. -L.; Stone, R. G. +8 more
The radio receiver of the Unified Radio and Plasma (URAP) experiment aboard the Ulysses spacecraft records spectra of the quasi-thermal plasma noise. The interpretation of these spectra allows the determination of the total electron density Ne and of the cold (core) electron temperature Tc in the solar wind. A single power law does not fit the var…
HEXE observations of active galactic nuclei : constraints on pairs and Compton reflection.
Pietsch, W.; Sunyaev, R.; Kendziorra, E. +10 more
We present results of X-ray observations of the three brightest Active Galaxies in hard X-rays, the quasar 3C 273 (1226+02), the Seyfert galaxy NGC 4151, and the radio galaxy Cen A (NGC 5128). The observations were made with the HEXE instrument (20-200 keV) on board the Mir space station. We discuss the spectra of the sources in the context of mod…
The HIPPARCOS Input Catalogue. III - Photometry
Grenon, M.; Mermilliod, J. C.; Mermilliod, M.
Photometric information about stars proposed for observation by the astrometric satellite Hipparcos is used for several purposes. Instrumental colors and magnitudes served as an input to the definition of the observing program (e.g. in defining the magnitude-limited survey), in optimizing the observations by allocating observing time according to …
From Fairall 9 to High-z Objects: Pattern of Change in Ionization Structure
Zheng, Wei; Binette, Luc; Fang, Li-Zhi
A study of 79 IUE spectra of the Seyfert galaxy Fairall 9 shows a considerable change in the continuum shape which can be characterized by several sections. The flux at 3075 A changes in approximate proportion to the optical and X-ray flux, suggesting that they may be a part of the power law. The apparent fourfold change in the continuum slope bet…
A search for the 2omega-omega frequency in the X-ray light curves of intermediate polars.
Hellier, Coel
Wynn and King (1992) have shown that diskless accretion gives rise to modulations at either the omega-Omega or 2omega-Omega frequencies in the X-ray light curves of intermediate polars. However, the EXOSAT archive shows no sign of a 2omega-Omega modulation in any of the systems observed. An omega-Omega modulation larger than half the spin-pulse am…
Volcanic Activity on Io at the Time of the Ulysses Encounter
Spencer, John R.; Howell, Robert R.; Klassen, David R. +2 more
The population of heavy ions in lo's torus is ultimately derived from lo volcanism. Ground-based infrared observations of lo between October 1991 and March 1992, contemporaneous with the 8 February 1992 Ulysses observations of the lo torus, show that volcanic thermal emission was at the low end of the normal range at all lo longitudes during this …
Hubble Space Telescope FOS Observations of KPD 0005+5106: A Subluminous WN-WC Descendant with Ongoing Mass Outflow?
Sion, Edward M.; Downes, Ronald A.
The results are reported of spectroscopic observations of the ultrahigh excitation, helium-rich, prewhite-dwarf KPD 0005 + 5106 obtained with the HST Faint Object Spectrograph (FOS) in 1991 May and July with the red (FOS/RD) and blue (FOS/BL) Digicon detectors. The data reveal a rich line spectrum both in absorption and in emission with ultra-high…