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HST Observation of Mg ⁺in Outburst from Comet D/Shoemaker-Levy 9

Stern, S. A.; Feldman, P. D.; Weaver, H. A. +1 more

Ultraviolet spectra of fragment G1 of Comet D/Shoemaker-Levy 9 taken 4 days before impact (on 14 July 1994) by the Faint Object Spectrograph of the Hubble Space Telescope show a brief outburst of magnesium ions. The Mg⁺emission decays back to its quiescent (undetectable) level with a time constant of ∼1 min, consistent with the ions bei…

Spectroscopic binary orbits from ultraviolet radial velocities. Paper 19: Mu1 Scorpii (HD 151890)

Sahade, J.; Stickland, D. J.; Henrichs, H.

Short-Term Chromospheric Variability in alpha Tauri (K5 III): Results from IUE Time Series Observations

Brown, Alexander; Cuntz, Manfred; Deeney, Bryan D. +1 more

We evaluate time series observations of chromospheric lines (Mg II, Mg I, and C II) for the K giant α Tau obtained using the IUE LWP camera at high dispersion. These observations cover a time span of about 2 weeks in 1994 February-March and were designed to resolve variations occurring within hours, days, and weeks. We consider the observational r…

Stars of the southern hemisphere proposed for the HIPPARCOS mission.

Rousseau, J. M.; Perie, J. P.; Gachard, M. T.

As part of the preparation for the Hipparcos mission, we determined the positions of 96800 already listed stars and 21265 previously unlisted companions, using information gathered by the ESO Quick Blue Survey. B1950 and J2000 system coordinates are given for each star. The magnitudes and spectral types are given in addition to the exact date of t…

ULYSSES at high latitudes: an overview of recent results

Smith, E. J.; Marsden, R. G.

After its fly-by of the planet Jupiter in February 1992, the Ulysses spacecraft is now in a highly inclined heliocentric orbit that will bring it above the south polar regions of the Sun in September 1994. The high-latitude phenomena observed to date have been strongly influenced by the near-minimum solar activity conditions encountered during thi…

Multiwavelength Observations of the Symbiotic Star AG Dra During 1979-1995

Greiner, J.; Altamore, A.; González-Riestra, R. +5 more

Since 1980 the high velocity symbiotic system AG Dra has undergone three phases of activity (or "outbursts") which were extensively observed in optical, ultraviolet and X-ray bands. We describe the historical light curve of the star, and summarize 17 years of UV monitoring with the IUE satellite.

Requirements for Investigating the Connection between Lyman-α Absorption Clouds and the Large-Scale Distribution of Galaxies

Green, Richard F.; Jannuzi, Buell T.; Sarajedini, Vicki L.

We model the requirements on observational data that would allow an accurate determination of the degree of association between Lyman-alpha absorbers and peaks in the redshift distribution of galaxies (large-scale structures like clusters of galaxies). We compare simulated distributions of low-redshift Lyman-alpha absorption systems, constrained t…

Magnetic field structure in the comet Grigg-Skjellerup pileup region

Coates, A. J.; Neubauer, F. M.; Israelevich, P. L. +1 more

The position of the Giotto spacecraft relative to comet Grigg-Skjellerup is found from the draping geometry based on the vector magnetic field data. It is shown that Giotto passed the cometary nucleus on the nightside. The behavior of the magnetic field vectors exhibits two different types in the pileup region. In the outer pileup region, the magn…

Spectral resolution improvement technique for a spectrograph mounting a discrete array detector

Naletto, Giampiero; Pernechele, Claudio; Poletto, Luca +1 more

A new technique has been developed for improving the spectral resolution of spectrographs mounting discrete array detectors. The basic concept is to acquire various spectroscopic images, each one being shifted on the detector by a fraction of the pixel (i.e., the detector resolution element), and to apply suitable numerical procedures in order to …

UV Observations of the Symbiotic Star EG And

Pereira, Claudio Bastos

EG And is a S-type symbiotic star. Here is present UV observations made by IUE from 1978 to 1991. From these observations the electronic density and the electronic temperature were obtained. The size of He II emitting region was estimated as 7.3R_⊙. Line and continuum variations confirm the binary nature of EG And.