Search Publications
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,…
The stellar population in the Wolf-Rayet knot in NGC 5430.
Keel, W. C.
The barred spiral NGC 5430 contains an extremely luminous H II region showing very strong He II and N III Wolf-Rayet (WR) emission features. Spectrophotometry from 1200 - 7000 Å has been obtained. From these data, limits on the reddening and effective temperature of the stellar population are derived; Teff is between 25000 and 35000K. N…
Solar-type giants : new X-ray detections from EXOSAT observations.
Gondoin, P.; Mangeney, A.; Praderie, F.
The authors report new X-ray detections of HD 1671 (F5 III) and HD 12929 (K2 III). From an analysis of X-ray count rates in three broadband filters from HD 203387, they derive an estimate of its coronal temperature of T ≡ 3×106K. The data show that HD 12929 (K2 III) differs from the earlier type stars which the authors observed in the f…
EXOSAT observations of a broad absorption-line quasar : PHL 5200.
Singh, K. P.; Westergaard, N. J.; Schnopper, H. W.
Results are presented of broadband (0.05-10 keV) observations of the high-redshift quasar PHL 5200 using the EXOSAT Observatory. In observations of the 45-arcmin (FWHM) region centered on this broad-absorption-line quasar, performed with the medium-energy (ME) and low-energy (LE) experiments, X-ray emission has been detected in the 2-6 keV energy …
The ultraviolet spectrum of the peculiar emission-line star GG Carinae.
Gosset, E.; Swings, J. -P.; Brandi, E.
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 EB-V = 0.52±0.04 (2σ). The cont…
IUE observations of the broad continuum feature at 1400 A in the silicon and related stars.
Shore, S. N.; Brown, D. N.
The upper main sequence chemically peculiar stars have previously been studied spectrophotometrically using low resolution TD-1 spectra. These show that the broad continuum feature at 1400 Å is a useful indicator of Si anomaly. In this paper the authors extend this to IUE low resolution spectra and show that this feature is indeed well correlated …
Physical parameters for Population II stars.
Cacciari, C.; Morossi, C.; Malagnini, M. L. +1 more
The observed energy distributions from the ultraviolet to the near-infrared for a number of Population II stars have been collected from the literature (Christensen, 1978; Cacciari, 1985) and have been compared with the Kurucz (1979) model atmospheres computed for different [M/H] ratios. Effective temperatures, surface gravities and apparent angul…