The ultraviolet spectrum of the peculiar emission-line star GG Carinae

This paper presents the first study of the properties of the peculiar emission-line star GG Carinae in the ultraviolet wavelength domain. From IUE high resolution spectra, the authors investigate the behaviour of different velocities. From IUE low resolution data, they propose a value of the B-V excess of E[SUB]B-V[/SUB] = 0.52±0.04 (2σ). The continuum of GG Car from the UV to the visible is rather well represented by the theoretical flux of a T[SUB]eff[/SUB] = 18,000K Kurucz standard model atmosphere. The authors investigate also the ultraviolet light curve, which is essentially similar to the one observed in the visible (Gosset et al., 1984, 1985)

On the multiplicity of the O-star Cyg OB2 #8A and its contribution to the gamma-ray source 3EG J2033+4118

We present the results of an intensive spectroscopic campaign in the optical waveband revealing that Cyg OB2 #8A is an O6 + O5.5 binary system with a period of about 21.9 d. Cyg OB2 #8A is a bright X-ray source, as well as a non-thermal radio emitter. We discuss the binarity of this star in the framework of a campaign devoted to the study of non-thermal emitters, from the radio waveband to gamma-rays. In this context, we attribute the non-thermal radio emission from this star to a population of relativistic electrons, accelerated by the shock of the wind-wind collision. These relativistic electrons could also be responsible for a putative gamma-ray emission through inverse Compton scattering of photospheric UV photons, thus contributing to the yet unidentified EGRET source 3EG J2033+4118.Comment: 8 pages, 4 figures, conference on "The Multiwavelength Approach to Gamma-Ray Sources", to appear in Ap&S

Observations of high redshift QSO’s

Time-consuming observations with existing large telescopes have shown that the spectra of quasistellar objects are exceedingly complex. A VLT is needed to obtain the highest spectral resolution and to study in detail the numerous absorption lines. Drs. Jean-Pierre Swings (Institut d'Astrophysique in Liege, Belgium) and Jean Surdej (ESO) would like to use their nights to investigate the nature ofsome of the most distant objects in the universe

Consideration of the forbidden lines of iron in the states from Fe0 to Fe6+

The iron atom which has a fairly high cosmic abundance presents the great interest of appearing in a wide variety of stars and nebulae, at many stages of ionization, and of revealing forbidden transitions in emission in many of these ionization stages. The present paper discusses the following topics : (a) the case of the as yet undiscovered forbidden lines of neutral iron (Fe0) ; (b) some recently acquired astronomical information on the forbidden lines of the stages Fe+ to Fe6+ ; (c) general considerations on the important information revealed by these forbidden lines of iron on the physical structure and excitation mechanisms which are present in the emission line stars of early and late types. For lack of time we give only a very summarized version of our paper ; a complete text will appear later

The emission lines in the ultraviolet region 3140-3500Å of CH Cygni, and related problems

peer reviewedThe M6 semi-regular variable CH Cygni had an outburst in June 1967. The emission lines of the ultraviolet region λ< 3500 Å are described. General considerations on the importance of this region are outlined

Possibility of Fluorescence Phenomena in the Ultraviolet Spectrum of Symbiotic Stars and Long Period Variables

We discuss essentially the cases where molecular fluorescences may be excited by Lyman α and other strong discrete ultraviolet emissions, including lines beyond the Lyman limit. The stars involved are the symbiotic objects and the long period variables. The molecules are H2, N2, O2, NO and CO which have their resonance systems in the ultraviolet.</jats:p

Is HD 45677 a variable star?

La magnitude photographique de HD 45677 a varié faiblement entre 1899 et 1969. L'amplitude n'a jamais dépassé 0.3 mag. Par contre, entre 1969 et 1971, HD 45677 a faibli d'approximativement une magnitude.Whereas HD 45677 has faded by approximately one magnitude since 1969, the amplitude of variation in photographic magnitude between 1899 and 1969 has always been smaller than 0.3 mag