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AI II as an electron density diagnostic for the upper chromosphere/lower transition region in late-type stars.
Doyle, J. G.; Keenan, F. P.; Harra, L. K. +2 more
The ratio of the Al II resonance line 3s2 1S-3sp 1P1 at 1670 A to the inter-system line 3s2 1S-3s3p 3P1 at 2669 A is a useful electron density diagnostic for N(e) greater than 10 exp 10/cu cm. However, it is also sensitive to the adopted electron temperature, and, in fact, should be a useful electron temperature diagnostic when Ne is not greater t…
Imaging Observations of Jupiter's Sodium Magneto-Nebula During the Ulysses Encounter
Mendillo, Michael; Flynn, Brian; Baumgardner, Jeffrey
Jupiter's great sodium nebula represents the largest visible structure traversed by the Ulysses spacecraft during its encounter with the planet in February 1992. Ground-based imaging conducted on Mount Haleakala, Hawaii, revealed a nebula that extended to at least ±300 Jovian radii (spanning ~50 million kilometers); it was somewhat smaller in scal…
Bartkevicius A., Sperauskas J., Rastorguev A.S., Tokovinin
Rastorguev, A. S.; Bartkevicius, A.; Sperauskas, J. +1 more
Radial velocity measurements are presented for 81 Population II stars. The sample comprises components of metal-poor binary stars, spectroscopic binary candidates, high latitude supergiants, metal-deficient stars with spectroscopic determinations of Fe/H, HIPPARCOS program stars, and some other stars of metal-poor population. The radial velocity m…
The continuum radiation of the symbiotic star AG Draconis in quiescence and during outbursts.
Leibowitz, E. M.; Formiggini, L.
Results of spectroscopic measurements of the continuum radiation of the symbiotic star AG Dra in the UV and optical regions are presented. The observations extend over a period of eight years and cover the quiescent state of the star as well as three outbursts which occurred during those years. The results suggest that outbursts of AG Dra are trig…
The Ionization Conditions in the Milky Way Halo: Infalling Gas toward the North Galactic Pole
Danly, Laura
The observations of gas in the Milky Way are reviewed with an eye toward the theoretical predictions of the Galactic Fountain model for the production of halo gas. Data are shown which indicate significant variations in the ionization conditions in infalling halo gas in the northern galactic hemisphere. Besides being interesting in its own right, …
EXOSAT Observations of the Broad-Line Radio Galaxy 3C 382
Ghosh, K. K.; Soundararajaperumal, S.
X-ray observations of the broad-line radio galaxy 3C 382 were carried out with EXOSAT on many occasions (>20) between 1983 and 1985. Low and Medium Energy (LE and ME) spectra of this source were obtained from the EXOSAT data base. The hard-X-ray luminosity light curve of 3C 382 which was constituted from Ariel V, HEAO 1, Einstein, EXOSAT, and G…
Absorption-Line Profiles in a Companion Spectrum of a Mass-losing Cool Supergiant
Boehm-Vitense, Erika; Rodrigues, Liliya L.
Cool star winds can best be observed in resonance absorption lines seen in the spectrum of a hot companion, due to the wind passing in front of the blue star. We calculated absorption line profiles that would be seen in the ultraviolet part of the blue companion spectrum. Line profiles are derived for different radial dependences of the cool star …
Geometrical stability and evolution of the HIPPARCOS telescope
Lindegren, L.; Le Poole, R. S.; Perryman, M. A. C. +1 more
A simple geometrical model of the Hipparcos telescope is described whereby the relative positions and orientations of critical optical elements can be derived from the field-to-grid transformation determined as part of the normal data processing. The instrument is very stable on time scales of hours, but secular drifts of the order of 0.1 micron/d…
Fe II Fluorescence and Anomalous C IV Doublet Intensities in Symbiotic Novae
Kafatos, M.; Michalitsianos, A. G.; Meier, S. R.
The variation of absolute intensities of Bowen-excited Fe II emission in the symbiotic stars RR Tel, RX Pup, and AG Peg is examined. The C IV doublet intensity ratios in RR Tel were not anomalous between 1979 and 1989, and the ratio had typical values within the optically thin range. The intensity of individual Fe II Bowen-excited lines is correla…
Electron distributions upstream of the comet Halley bow shock: Evidence for adiabatic heating
Anderson, K. A.; Neubauer, F. M.; Glassmeier, K. H. +4 more
We report on three-dimensional plasma electron (22 eV to 30 keV) observations upstream of the comet Halley bow shock, obtained by the RPA-1 COPERNIC (Rème Plasma Analyzer-Complete Positive Ion, Electron and Ram Negative Ion Measurements near Comet Halley) experiment on the Giotto spacecraft. Besides electron distributions typical of the undisturbe…