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Hard X-ray observations of the quasar 3C 273.
Damle, S. V.; Kunte, P. K.; Naranan, S. +2 more
The quasar 3C 273 was observed with a balloon-borne phoswich scintillator detector system launched on December 12, 1983 from Hyderabad, India. 3C 273 was tracked for 130 minutes and the background was measured in the same ranges of elevation and azimuth when the source was not in the field of view, for approximately the same duration. The fluxes i…
A study of UV spectra of zeta Aur/VV CEP stars. X. Mass-loss of alphaSco A from high-resolution IUE spectra of alpha SCO B.
Reimers, D.; Hagen, H. -J.; Hempe, K.
We redetermine the rate of mass-loss of the M super- giant α Sco by means of circumstellar lines observed with IUE in the ultraviolet spectrum of its B star companion. We first show 1) that nearly all UV lines, on which previous mass-loss determinations (v.d. Hucht et al., 1978; Bernat, 1982) were based, are blends with interstellar lines and 2) t…
Detailed Analysis of a Surface Feature on Comet p/ Halley
Wilhelm, K.; Keller, H. U.; Schwarz, G. +9 more
The surface of the nucleus of comet P/Halley is visible on many images taken by the Halley Multicolour Camera on board the Giotto spacecraft. A number of structural features like "mountains" or "surface dips" are clearly discernible. This paper outlines the methods that can be applied to analyze a surface feature with the aim of obtaining its char…
The rapidly oscillating AP stars as a test of stellar chromospheric heating mechanisms.
Sonneborn, G.; Shore, S. N.; Brown, D. N. +1 more
The discovery of a new class of magnetic stars, the rapidly pulsating Ap stars, provides an unprecedented tool for the study of Alfvénic heating in the outer atmospheres of main sequence stars. In this note, the authors point out that detection of rotationally modulated chromospheric emission line fluxes, especially the Ca II, Mg II, and C IV line…
X-ray and UV observations of omega Centauri with EXOSAT.
Koch-Miramond, L.; Auriere, M.
The globular cluster ω Cen has been observed on two occasions, 6 months apart, with the Channel Multiplier Array on board EXOSAT, in the energy band 0.02 keV - 2.5 keV. The aim of the present investigation is to study the diffuse emission as well as the point sources discovered in the X-ray range with the EINSTEIN satellite (Hartwick et al., 1982)…
Line blanketed model atmospheres of Ap-stars. VI. HD 221568.
Muthsam, H.; Stepien, K.
Visual and UV spectroscopic observations of HD 221568 together with line blanketed model atmospheres show that the star has an effective temperature of 10300K if log g = 3.7 is assumed. The temperature may be lower by about 100K in the phase of reddest B-V. Models with variable chemical composition are not able to reproduce observed light variatio…
The Upstream Region Foreshock and Bow Shock Wave at Comet p/ Halley from Plasma Electron Measurements
Anderson, K. A.; Reme, H.; Korth, A. +7 more
We survey the plasma electron parameters from a distance 2.7 × 106 km from the comet nucleus to the bow shock wave at about 1.1 × 106 km and somewhat beyond. We describe the features of the electron foreshock lying outside the shock to a distance of about 230,000 km. It is a region of intense solar wind-comet plasma interacti…
Cosmic ray gradients in the outer Galaxy
Wolfendale, A. W.; Mayer, C. J.; Richardson, K. M. +2 more
The release of basic cosmic gamma ray data from the COS B satellite experiment has enabled a more detailed analysis than hitherto of the problem of variations of cosmic ray intensity locally and in the Outer Galaxy. It is found that there is still evidence for a modest cosmic ray gradient, particularly at the highest gamma ray energies where the p…
Different regions of line formation in the envelope of the early emission line star HD 190073.
Ringuelet, A. E.; Rovira, M.; Cidale, L. +1 more
A description is presented of the spectral features that characterize the spectrum of HD 190073 both in the photographic region from about 3600 Å to about 6600 Å, and in the IUE ultraviolet, from about 1150 to about 3200 Å. A number of different types of profiles can be distinguished and this seems to imply that many different "broad" regions of l…
Analysis of the MG II resonance lines in the spectrum of Sirius.
Talavera, A.; Freire Ferrero, R.; Gouttebroze, P.
The atmospheric layers above the photosphere of Sirius A (Alpha CMa, AlV) are analyzed using high-resolution spectra of the Mg II resonance lines obtained with the Copernicus and IUE satellites. The line cores are formed at optical depths so small that an extension of the existing photospheric models for Sirius is necessary. Two tentative sets of …