Search Publications
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…
Pick-up ions at Comet P/Halley's bow shock - Observations with the IIS spectrometer on Giotto
Johnstone, A.; Borg, H.; Amata, E. +2 more
Gaseous material expanding from the nucleus of Comet Halley into space forms the neutral coma around the comet. Ionization in the solar UV radiation removes particles from the coma and injects them into the solar wind plasma. These freshly created ions are accelerated by the interplanetary electric field on cycloidal trajectories with gyrocenters …
Density and brightness distribution of cometary dust tails
Keller, H. U.; Richter, K.
The density and brightness distributions of cometary dust tails are studied, assuming that the terminal velocity of a dust particle depends on emission time, particle size, and two angles defining the direction of emission. In the novel method, Keplerian trajectories are used for the particles rather than approximations. The corresponding Jacobian…
Upper limit to the boron abundance in the population II star HD 140283.
Molaro, P.
A high resolution IUE spectrum of the Population II star HD 140283 has been analyzed to search for the B I 2496 Å resonance doublet. No features attributable to this element have been found. An upper limit for the B abundance of B/H < 10-11, i.e. more than one order of magnitude less than the solar value has been derived. The presenc…
Hot Ions Observed by the Giotto Ion Mass Spectrometer at the Comet p/ Halley Contact Surface
Balsiger, H.; Young, D. T.; Goldstein, B. E. +6 more
Just inside the contact surface (∼ 4700 km) the High Energy Range Spectrometer (HERS) sensor of the Giotto Ion Mass Spectrometer (IMS) detected a sudden, intense burst of ions that lasted until the HERS sensor ceased transmitting data at a distance of ∼ 3000 km from comet P/Hallley. During this brief interval ions with M/Q = 1,2, 12, 14, 16-19,24,…