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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…
IUE Observations of Comet p/ Halley - Evolution of the Ultraviolet Spectrum Between 1985SEP and 1986JUL
Feldman, P. D.; A'Hearn, M. F.; Schleicher, D. G. +13 more
The ultraviolet spectrum of comet P/Halley (1982 i) was monitored with the International Ultraviolet Explorer (IUE) satellite observatory between 1985 September 12 and 1986 July 8 (r < 2.6 AU pre- and post-perihelion) at regular time intervals except for a two-month period around the time of perihelion. A complete characterization of the UV spe…
Expansion Velocity and Temperatures of Gas and Ions Measured in the Coma of Comet p/ Halley
Berthelier, J. J.; Eberhardt, P.; Krankowsky, D. +9 more
In situ measurements of flow velocity and temperature in the inner coma were obtained from ram energy spectra of molecules and ions observed by the NMS experiment onboard the Giotto probe to comet Halley. Radial flow speed was (800 ± 50) m s-1 at distances from the nucleus between 1000km and 4000 km. Whereas ions became stagnant just ou…
Soft X-ray transients in quiescence : observations of AQL X-1 and CenX-4.
van Paradijs, J.; Verbunt, F.; Arnaud, K. A. +1 more
The authors observed the soft X-ray transients Aql X-1 and Cen X-4 during quiescence with EXOSAT. For Aql X-1 they obtain a 3σ upper limit to the X-ray luminosity Lx (in the energy range between 0.5 and 4.5 keV) of <3.0×1033erg s-1, Cen X-4 was detected at Lx (0.5 - 4.5 keV) ≅ 1.5 to 4.2×1033
Giotto magnetic-field results on the boundaries of the pile-up region and the magnetic cavity
Neubauer, F. M.
Data from Giotto's magnetometer collected during the encounter at Comet Halley on March 13/14, 1986, were used to investigate the most conspicuous boundaries in the inner plasma region surronding Comet Halley, i.e., the pile-up boundary and the ionopause. The normal vectors at the boundary crossings were determined using the minimum variance techn…