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The spectrum of the VV Cephei star KQ Puppis (Boss 1985). III. A possible model.
Altamore, A.; Rossi, C.; Baratta, G. B. +2 more
Following a previous study by Altamore et al. of the ultraviolet spectrum of KQ Pup, and the spectral Atlas of this star by Altamore et al., the authors analyze coudé and CAT CES optical spectra of the object observed during 1969-1984, and compare with IUE data obtained in 1979. The ultraviolet to infrared energy distribution appears bimodal with …
Geometrical calibration and assessment of the stability of the HIPPARCOS payload
Schrijver, Hans; van der Marel, Hans
The various geometrical calibrations of the Hipparcos telescope and detection system are described. It is shown that these calibrations can be executed with the required precision of better than a milli-arcsecond. Moreover, it is shown that variations in the parameters describing the calibration results are very slow, yielding the picture of a ver…
X-Ray Continuum and Line Emission of the Seyfert Galaxy MCG-5-23-16
Singh, K. P.; Rao, A. R.; Vahia, M. N.
We report observations of X-ray continuum and line emission from the highly absorbed and variable Seyfert galaxy MCG -5-23-16, using the low- energy and the medium-energy detectors of the EXOSAT Observatory. The galaxy was observed in 1983 December and in 1984 May. The X-ray intensity of the source is observed to vary by ~25% in the hard (2-10 keV…
Attitude determination in the HIPPARCOS revised mission
Donati, F.; Falin, J. L.; Kovalevsky, J. +2 more
An accurate knowledge of the attitude as determined by the observation of star transits through the star mapper is an essential factor in the final accuracy of the Hipparcos reductions. In comparison with the nominal mission, several features tend to degrade the precision of the attitude determination: an irregular increase of the background noise…
Resolution of the southern radio lobe of 3C 33 at 660 NM
Stiavelli, Massimo; Crane, Phillipe
An HST planetary camera image of the southern radio lobe of 3C 33 has revealed a strand of emission coincident with the peak in the radio emission at 2 and 6 cm. The detailed morphological similarity between the optical and radio data confirms beyond doubt the common origin of the radio and optical emission, and raises the question of the physical…
Properties of fast winds in hot stars in the Magellanic Clouds.
Patriarchi, P.; Perinotto, M.
The early-type stars in the Magellanic Clouds for which good quality high-resolution spectra with the IUE satellite exist have been studied for their stellar wind. Their P Cygni profiles in the N V, C IV, Si IV, O V, and N IV lines have been investigated with the SEI (Sobolev plus exact integration) method. Particularly good fits of the theoretica…
Ion-cyclotron waves at Jupiter: Possibility of detection by Ulysses
Horne, Richard B.; Thorne, Richard M.; Mei, Yi
We evaluate the convective growth of ion-cyclotron waves in the Io plasma torus using realistic plasma parameters. Significant wave amplification is restricted to two dominant frequency bands. As originally proposed by Thorne and Moses [1983,1985], waves between the O+ and H+ gyro-frequencies may be excited at higher latitude…
Multiwavelength observations of the quasar Q 1821+643 during the ROSAT All Sky Survey.
Malkan, M. A.; Ulrich, M. -H.; Heidt, J. +4 more
Temporal variations of the flux in the optical, UV, soft X-ray and medium X-ray ranges occur in most AGN studied, but no general correlation has emerged between the variations in these different energy ranges. Because of its high ecliptic latitude the radio-quiet quasar Q 1821 + 643 was surveyed for 37 days by ROSAT during the ROSAT All Sky Survey…
Solar particle composition: Measurements in the March 1991 event at 2.5AU
Forsyth, R.; Tappin, S. J.; Lanzerotti, L. J. +3 more
The time evolution of the very large solar particle event occurring on days 82-90 (March 23-31), 1991, as measured at 2.5 AU by the instrumentation on the Ulysses spacecraft was quite complex. Measurements by the HI-SCALE instrument of the nuclear composition (emphasizing Z≥6) of the interplanetary particles at a time resolution of two hours provi…
Detection of a White Dwarf in a Visual Binary System
Boehm-Vitense, Erika
The F6 giant HD 160365 was detected to have a white dwarf companion about 8 arcsec south of the star. The UV energy distribution observed with IUE shows that the white dwarf has an effective temperature of 23,000 +/- 2000 K. If log g = 8 the Lya profile indicates an effective temperature around 24,500 K. Using the theoretical models by Wesemael et…