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The circumstellar environment of the Herbig Ae/Be stars. The case of AB Aurigae.
Fonti, S.; Blanco, A.; Strafella, F.
The possibility that the near-infrared excess observed for AB Aur is due to free-free emission coming from a circumstellar H I region is investigated. The analysis of absorption lines (mainly of Fe II) present in IUE spectra shows that both the derived column densities and the excitation temperature (about 2000 K) indicate the presence of a conspi…
Erratum - a 23H EXOSAT Observation of the X-Ray Pulsar 1E:2259+586 and the Associated Supernova Remnant G:109.1-1.0
Coe, M. J.; Dennerl, K.; Hanson, C. G. +1 more
SC 2059-247 : no evidence for cluster evolution or extreme X-ray properties.
Kaastra, J. S.; de Korte, P. A. J.
The southern cluster SC 2059-247 has been observed by the X-ray satellite EXOSAT. The cluster has a high luminosity and cooling mass flow and a small core radius, but it has neither exceptional properties compared to other clusters, nor does it show signs of evolution effects, as was concluded from earlier Einstein observations.
Detection of energetic electron (E greater than KeV) and ion fluxes (E greater than 97 KeV) from comet P/Halley by the Giotto experiment EPA on 1986 March 13/14
Neubauer, F. M.; Kirsch, E.; O'Sullivan, D. +2 more
Relativistic electron fluxes (greater than 220, greater than 300 KeV) were recorded during the Giotto encounter with comet P/Halley from the inbound to the outbound bowshock. A strong enhancement in the greater than 300 KeV electron flux was measured about 1 hr after the outbound crossing of the bow shock. It is suggested that the electrons were s…
Comet P/Halley's nucleus and its activity
Keller, H. U.; Reitsema, H. J.; Delamere, W. A. +2 more
The Halley Multicolour Camera on board ESA's Giotto spacecraft observed the nucleus of comet P/Halley and its environment and returned more than 2000 images. The observations are summarized, their calibration is described, the status of the analysis and the results are discussed. Topographic features on the nuclear surface and areas of activity ar…
To CO and N2 Abundance in Comet p/ Halley
Berthelier, J. J.; Eberhardt, P.; Krankowsky, D. +8 more
A preliminary evaluation of the mass 28 amu/e signal observed in the neutral mode of the Giotto neutral gas mass spectrometer (NMS) is presented. At 1000 km from the nucleus the authors obtain for the CO number density n(CO)/n(H2O) ≤ 0.07. The production rate of CO as parent molecule directly from the nucleus is thus less than 7% of the…
The dust distribution within the inner coma of comet P/Halley 1982i - Encounter by Giotto's impact detectors
Zarnecki, J. C.; Wallis, M. K.; Sekanina, Z. +12 more
Analysis of the data from Giotto's Dust Impact Detection System experiment (DIDSY) is presented. These data represent measurement of the size of dust grains incident on the Giotto dust shield along its trajectory through the coma of comet P/Halley on 1986 March 13/14. First detection occurred at some 287,000 km distance from the nucleus on the inb…
Evidence for methane and ammonia in the coma of comet P/Halley
Ip, W. -H.; Allen, M.; Yung, Y. +2 more
Methane and ammonia abundances in the coma of Halley are derived from Giotto IMS data using an Eulerian model of chemical and physical processes inside the contact surface to simulate Giotto HIS ion mass spectral data for mass-to-charge ratios (m/q) from 15 to 19. The ratio (m/q) = 19/18 as a function of distance from the nucleus is not reproduced…
Magnetic structure in cool stars. XII - Chromospheric activity and rotation of giants and dwarfs
Rutten, R. G. M.
The relation between the Ca II H and K line-core flux density and rotation rate is studied for 313 F- to M-type stars ranging in luminosity class from II-III to V. The activity-rotation relation for Ca II is compared with similar relations for Mg II and soft X-rays. Dwarfs and the majority of the giants studied follow the same color-dependent rela…
Rotational modulation and flares on RS CVn and BY DRA stars. III. IUEobserations of V711 Tau = (HR 1099), II Peg and AR Lac.
Doyle, J. G.; Linsky, J. L.; Simon, T. +8 more
The authors present observations of three RS CVn stars, which were obtained over the stellar rotation cycles with the IUE satellite. Emission lines from high-temperature transition regions and chromospheres analogous to those observed in the solar spectrum were observed. However, the stellar line surface fluxes are hundreds of times the solar valu…