Search Publications
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 …
Rotational modulation of the wind of the PMS star AB AUR : new observations in C IV and MG II.
Catala, C.; Felenbok, P.; Praderie, F.
In continuation of a time monitoring program devoted to short-term spectral variability in Herbig pre-main-sequence stars, new results are presented for the star AB Aur. On a one day time scale, the variability of the blue edge velocity of the Mg II 2795-A line is confirmed, and that of the C IV 1548-A line established. Since the observations cove…
The relation between optical and X-ray flux variations of the black-hole candidate LMC X-3.
Maraschi, L.; Motch, C.; van Paradijs, J. +9 more
The authors present the results of V-band photometry of the optical counterpart of the black-hole candidate LMC X-3. The observations were made during a three-week period in December 1984, using CCD cameras at the Danish 1.5 m, and MPI 2.2 m telescopes at ESO, and the 1.0 m telescope at SAAO. In addition to an orbital brightness modulation of 0.15…
The peculiar emission-line supergiant HD 37836.
Stahl, O.; Wolf, B.
The luminous emission-line star HD 37836 of the LMC has been studied using high-dispersion spectra in the UV and in the optical. In addition, IUE low-dispersion spectra and UBVRIJHKL photometry have been used to study the energy distribution. The emission-line spectrum of the star is very peculiar. Its UV absorption-line spectrum is more normal an…
Study of multiple nucleus galaxies. II. MKN 739.
Kollatschny, W.; Fricke, K. J.; Netzer, Hagai
An investigation of the Markarian galaxy MKn 739 is reported. The investigation used spectroscopic data from ground and space, radio observations, IRAS data and CCD imaging. Component A is a Seyfert type 1 nucleus with strong Fe II lines, very steep continuum and no trace of Lyman alpha and CIV 1549. Component B is a starburst nucleus, quite simil…
The central X-ray source in M 33.
Pietsch, W.; Hasinger, G.; Gottwald, M.
The Local Group galaxy M33 was observed with the European X-ray observatory Exosat. Two of the previously reported 11 X-ray sources in M33 were detected; analysis confirmed the dominance of the source M33 X-8, which coincides with the nucleus of M33. With an 0.1-6 keV X-ray luminosity of about 1.5 x 10 to the 39th erg/s, it is the brightest steady…
Secondary Electron Emission Induced by Gas and Dust Impacts on Giotto VEGA-1 and VEGA-2 in the Environment of Comet p/ Halley
McDonnell, J. A. M.; Grard, R. J. L.; Grun, E. +1 more
Giotto, Vega-1 and Vega-2 have been bombarded by a flow of gas and dust particles during their flyby of comet Halley. The emission of secondary electrons and sputtered ions caused by the large impact velocities (70-80 km s-1) perturbed the plasma density in the spacecraft vicinity and was a possible source of interference for electric f…