Search Publications
Non-LTE abundance analysis of the early-type high galactic latitude star HD 100340.
Dufton, P. L.; Lennon, D. J.; Keenan, F. P. +2 more
Stellar equivalent widths and line profiles, measured from high resolution AAT and IUE spectra, are used in conjunction with non-LTE and LTE model atmosphere calculations to estimate the atmospheric parameters and chemical composition of the early-type high galactic latitude star HD 100340. The effective temperature (Teff= 25000K), surf…
EXOSAT observations of the 1983 outburst of the rapid burster : a newmode of behaviour.
Haberl, F.; Stella, L.; Parmar, A. N. +4 more
The results of three observations of the rapid burster (MXB 1730-335) made in August 1983 are reported. A new mode of behavior consisting of strong persistent emission at a level of about 5 microJY along with type I bursts recurring approximately every 80 minutes, is reported. No type II bursts were seen during this interval. The spectrum of the p…
The interpretation of the UV light of elliptical galaxies.
Kjaergaard, P.
The UV spectra of the dwarf elliptical M 32 and the two Virgo giant ellipticals NGC 4472 and NGC 4649 are discussed using the spectrum synthesis technique in the whole wavelength region from 1500 A to 2.3 microns. For M 32, the UV spectrum may be explained in terms of evolved blue stars from a minor metal-poor component together with a small contr…
The diffusion of gallium in main-sequence peculiar stars.
Artru, M. -C.; Alecian, G.
New observations of the gallium abundance in main-sequence peculiar stars are now available in the literature. The present paper analyses these new data in the framework of the diffusion processes. The radiative accelerations of gallium are computed, with up-to-date gallium line data, in various physical conditions of stable main-sequence star atm…
Fine dust structures in the emission of comet P/Halley observed by the Halley Multicolour Camera on board Giotto
Keller, H. U.; Thomas, N.
Halley Multicolor Camera (HMC) observations on board the ESA Giotto spacecraft provided images of comet P/Halley with resolution 4-orders of magnitude better than from the ground in March 1986. The fine structure seen in the emission from the cometary surface has led to some confusion over the nomenclature of jets and jet-like features streaming f…
Giotto / IMS Observations of Ion Flow Velocities and Temperatures Outside the Magnetic Cavity of Comet p/ Halley
Schwenn, R.; Balsiger, H.; Goldstein, B. E. +8 more
Fluid parameters for He2+ ions obtained from the Giotto Ion Mass Spectrometer HERS sensor are presented; also investigated are proton densities and velocities and thermal speeds of protons, alpha particles, and heavy ions in the hour before closest approach. A bow shock transition lasting ten minutes is observed. A region of enhanced He…
The UV high resolution spectrum of A-type supergiants.
Talavera, A.; Gomez de Castro, A. I.
A study of all the A-supergiants observed with IUE at high resolution shows that they can be divided into two groups: stars which show evidence of wind and mass-loss, and stars which do not show these characteristics. In the first group the resonance lines of Mg II, Fe II, Si II, C II are asymmetric, showing variable shortward shifted components. …
A spectral study of the persistent X-ray flux from 4U/MXB 1636-53.
van Paradijs, J.; Lewin, W. H. G.; Vacca, W. D. +3 more
The authors present a spectral analysis of the persistent X-ray flux from the X-ray burst source 4U/MXB 1636-53, which was continuously observed with EXOSAT for about 25 h in May 1984. They find that no standard one-component spectral model provides an acceptable representation of all the data. However, almost all "complex one-component" and "two-…
X-ray/optical brightness trends in 3C 66A.
Maccagni, D.; Tarenghi, M.; Garilli, B. +1 more
New X-ray and optical observations of the BL Lac object 3C 66A show small amplitude (≡30%) variability occurring probably contemporaneously in both ranges. The time scale is of the order of a week. This indicates that small intensity variations engage the whole electromagnetic spectrum of the source between visible and X-ray wavelengths, while lar…
Temporal variability of the massive X-ray binary 4U 1700-37.
Brinkmann, W.; Doll, H.
Results of a study of the time variability of the X-ray flux from the massive X-ray binary 4U 1700-37/HD 153919 from observations with the EXOSAT satellite are presented. Three types of intensity variations can be distinguished: flaring on time scales of 25 min to 2 h, flickering on time scales equal or less than 10 min with an amplitude equal or …