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Bulk properties and velocity distributions of water group ions at comet Halley: Giotto measurements.
Coates, A. J.; Glassmeier, K. -H.; Wilken, B. +3 more
In the region upstream of comet Halley, pickup heavy ions of cometary origin were directly observed by the Implanted Ion Spectrometer on Giotto. Here the authors discuss diffusion of this population in pitch angle and in energy, during the approach to the comet and on the outbound leg. The two data sets are compared and qualitative ideas on scatte…
The IRAS Low-Resolution Spectra of Planetary Nebulae
Volk, Kevin; Cohen, Martin
This paper presents the low-resolution spectra of 170 planetary nebulae observed by IRAS, most of which were not included in the Atlas of Low-Resolution Spectra. These have been classified into eight groups based upon the spectral morphology, with emphasis on the dust continuum rather than the spectral lines. The Low-Resolution Spectrometer (LRS) …
HM Sagittae : the evolution of a symbiotic nova.
Vogel, M.; Nussbaumer, H.
HM Sge was discovered in 1975, when it became a symbiotic nova. HM Sge is still evolving. Since its discovery, significant spectral changes have taken place in the ultraviolet, the radio, as well as in the visual wavelength ranges. Here, IUE observations from 1982 to 1989 are reported. The implications of the available spectral information since t…
Observations of the new luminous blue variable R 110 of the Large Magellanic Cloud during an F star-phase.
Stahl, O.; Wolf, B.; Cassatella, A. +2 more
The LMC star R 110 has increased its visual brightness by about 0.5 mag in the last ten years. During its brightest observed phase in January and February 1989, we obtained UBVRI and JHK photometry, low dispersion spectroscopy with IUE, and high dispersion spectroscopy in the optical with CASPEC and in the satellite UV with IUE. During the brighte…
MG II Observed in the Local Interstellar Medium: The Local Cloud
Molaro, P.; Beckman, J. E.; Vladilo, G. +1 more
Observations of interstellar absorptions superposed on the chromospheric Mg II emissions of nearby cool stars have been used to explore the structure of the local interstellar medium along many lines of sight. The interstellar cloud in which the sun is immersed (the 'local cloud', hereafter LC) has not previously been detected using this technique…
Localization of one of the galactic centre X-ray burst sources.
Skinner, G. K.; Eyles, C. J.; Foster, A. J. +1 more
Observations of an X-ray burst which occurred during the Spacelab-2 observations of the Galactic Center region are reported, and it is shown that it originated in the more southerly component of a previously reported persistent X-ray object, now resolved into two sources separated by 3 arcmin. Present knowledge of the number and location of the Ga…
Ultraviolet variability of NGC 4151 : a study using principal component analysis.
Penston, M. V.; Snijders, M. A. J.; Mittaz, J. P. D.
In an attempt at a decomposition of the different sources of variation in the spectra of NGC 4151, we have carried out a principal component analysis of spectra, seeking the number and form of the significant linearly independent spectra that are needed to reconstruct the data within the errors. Methods are outlined with particular emphasis on the…
Ultraviolet Interstellar Absorption toward HD 163522, a Halo Star at 9 Kiloparsecs in the Direction L = 350 and B = -9
Savage, Blair D.; Sembach, Kenneth; Massa, Derck
UV interstellar absorption line measurements obtained by the IUE satellite toward HD 163522 in the direction l = 349.6 deg and b = -9 deg are analyzed. The UV stellar spectrum of HD 163522 places the star beyond the Galactic center at a distance away from the Galactic plane of z = -1.5 kpc. An absorption-line spectrum with S/N approximately equal …
The mass ratio of nu SGR from ultraviolet radial velocities.
Jeffery, C. S.; Dudley, R. E.
The first positive determination of the secondary orbit of the hydrogen-deficient binary υ Sgr has been achieved by the application of cross-correlation methods to high-resolution ultraviolet (UV) spectra obtained with IUE. The mass ratio thus obtained (q = 0.63±0.01) and the consequent minimum mass for the primary (Mp sin3i/…
Ultraviolet spectra of a large sample of quasars - II. Variability ofLy-alpha and C IV emission lines.
Gondhalekar, P. M.
The analysis of spectra of 34 quasars observed more than once with IUE is presented. The Lyα + N V and C IV emission lines in the spectra of some quasars in this sample change in intensity over a short time-scale. This time-scale is comparable to the time-scale for change observed in the intensity of emission lines in the spectra of low-luminosity…