Search Publications

Erratum: Velocity space diffusion of pickup ions from the water group at comet Halley'' [J. Geophys. Res. 94, 9983 (1988)]

Coates, A. J.; Glassmeier, K. -H.; Wilken, B. +2 more

Large dust particles along the Giotto trajectory

Keller, H. U.; Curdt, W.

Images of Comet Halley taken by the Halley Multicolour Camera (HMC) onboard ESA's Giotto spacecraft provide highly accurate information on the viewing direction. As a part of the spacecraft dynamical system, HMC was very sensitive to attitude variations that occurred during the final approach phase. HMC identified several discrete events that were…

Plasma flow inside Comet P/Halley

Johnstone, A.; Amata, E.; Formisano, V. +2 more

The plasma flow parameters (bulk velocity, number density, temperature) have been computed from the Giotto JPA data for the solar wind protons and for the water group cometary implanted ions. The decrease of the plasma bulk speed due to mass loading is followed from the bow shock at 1.16 x 10 to the 6th km from the nucleus down to well inside the …

EXOSAT observations of a long X-ray burst from XB 1905+000.

Ilovaisky, S. A.; Chevalier, C.

During a 17-hour continuous Exosat observation of the faint X-ray source XB 1905 + 000 a single burst was detected which shows a long decay following a radius expansion-contraction phase near maximum bolometric flux. The best spectral fits for the persistent emission are found when a 10-percent contribution from a cool blackbody component is added…

Chromospheres of Two Red Giants in NGC 6752

Smith, Graeme H.; Dupree, A. K.; Jordan, Carole +3 more

Two red giant stars, A31 and A59, in the globular cluster NGC 6752 exhibit Mg II (2800 A) emission with surface fluxes comparable to those observed among metal-deficient halo field giants, and among low-activity Population I giants. Optical echelle spectra of these cluster giants reveal emission in the core of the Ca II K (3933.7 A) line, and in t…

Period Measurements of the 50 Millisecond Pulsar PSR 0540-69 with the EXOSAT Satellite

Hasinger, Guenther; Oegelman, Hakki

The period of the 50 ms pulsar PSR 0540 - 69 in the Large Magellanic Cloud was determined using five separate X-ray observations with the Exosat satellite in the interval August 12, 1984 to June 30, 1985. Together with Einstein observations and contemporaneous optical data, the Exosat periods can be fitted well to a quadratic curve yielding a brak…

The Complex 0.4--12 keV X-Ray Spectrum of Cygnus X-1

van der Woerd, H.; Barr, P.

Simultaneous observations of the 0.4-2 keV and 2-12 low-state spectrum of Cygnus X-1, made with the low-energy transmission grating spectrometer and gas scintillation proportional counter on board EXOSAT, are presented. At least four spectral components are required to describe the data: a hard (energy spectral index alpha about 0.4) power law dom…

High-velocity gas components towards 4 Lac.

Keenan, F. P.; Bates, B.; Catney, M. G.

A comparison of IUE ultraviolet spectra of the star 4 Lac with observations of a suitable comparison star have confirmed the presence of 'high-velocity gas components' in the former which are redshifted by a velocity about 100 km/s from the low-velocity interstellar gas. In addition to providing an unambiguous identification of the species which s…

Analysis of the COS B Data for Evidence of Linear Polarization of VELA Pulsar Gamma Rays

Mattox, John R.; Mayer-Hasselwander, Hans A.; Strong, Andy W.

The COS B spark chamber telescope observations of the Vela pulsar were analyzed for gamma-ray polarization. No significant quadrupole moment is found in the azimuthal distribution of the electron-positron pair production planes. However, analysis of the sensitivity indicates that even 100-percent polarization would not be detected. Therefore, the …

Is V426 Ophiuchi really an intermediate polar ?

Hellier, Coel; O'Donoghue, Darragh; Buckley, David +1 more

The dwarf nova V426 Oph has been proposed as an intermediate polar with a report of a 60-min period in the X-ray band. Optical photometry and spectroscopy show no evidence for such a period. Additionally, reanalysis of the X-ray data shows that the 60-min period is not significant and that the variability is consistent with flickering. Overall, no…