Search Publications
Dust emission of Comet Halley at large heliocentric distances
Gruen, E.; Schwehm, G.; Massonne, L. +2 more
Comet Halley is currently approaching the inner solar system. Four spacecrafts (NASA's spacecraft, two Russian Vega probes and the Japanese MS-T5 spacecraft) have already been launched to encounter the comet in March 1986. Two additional Halley probes (the European Giotto spacecraft and another Japanese Planet-A probe) will be launched in mid-85 t…
Einstein and EXOSAT observations of geminga (1E0630+178). A summary of the short - and medium - term variability data
Caraveo, P. A.; Bignami, G. F.; Mereghetti, S. +1 more
The X-ray source 1E 0630 + 178 was discovered by Bignami et al. (1983) during an X-ray survey. The survey was conducted with the aid of the Einstein Observatory. The involved field was also observed with the Exosat satellite in September 1983, when both Low Energy telescopes were still operating. The Einstein and Exosat data bases were utilized in…
EXOSAT- Present Status and Future Prospects
Redfern, R. M.
The design and operation of the ESA Exosat orbiting X-ray observatory (launched in May 1983) are reviewed, and some preliminary results are summarized. The value of X-ray observations for investigating hot sources assumed to be driven by accretion into neutron stars is indicated; the low-energy imaging telescopes, medium -energy experiment, and ga…
Abondances NLTE de Ca, Mg, C, Si dans quelques étoiles A.
Freire Ferrero, R.
Some results on Ca, Mg, C and Si abundances are given for some A stars of the solar neighbourhood. The abundances are determined via the comparison of computed and observed line resonance profiles, in the framework of the NLTE theory, with atom models reduced to a few atomic levels. The obtained NLTE abundance values are then compared to the LTE o…
X-Ray Spectrum of the TYCHO SNR Observed with EXOSAT
Robba, N. R.; Taylor, B. G.; Morini, M. +2 more
The Gas Scintillation and Medium Energy instruments onboard EXOSAT measured the continuum and line emission spectrum in the Tycho supernova remnant. For the first time the iron line at 6.53 keV is clearly resolved from the continuum, in addition to the lines from S, Ar and Ca. The comparison with a non-equilibrium ionisation model (Hamilton et al …
A search for X-ray emitting coronal structures in algol
Parmar, A. N.; White, N. E.; Culhane, J. L. +3 more
Algol was observed with the low energy imaging X-ray telescope and the medium energy detectors on the ESA EKOSAT spacecraft during the time of secondary optical eclipse when the B star passes in front of its K type companion. An examination of the X-ray light curves allows us to set preliminary lower limits to the size of an X-ray emitting corona …
Space Telescope observations of aurorae on the giant planets
Caldwell, J.; Wagener, R.
For the distant giant planets, Uranus and Neptune, the observation of aurorae may be the best astronomical technique for the detection of planetary magnetic fields, with implications for the structure and composition of their interiors. Aurorae may be detected by emssion of H I Ly α (1216 Å) and by H2 bands near 1600 Å. The latter are i…
Constraints on the Galactic Distribution of Cosmic Rays from the Cos-B Gamma-Ray Data
Strong, A. W.; Hermsen, W.; Lebrun, F. +7 more
The diffuse component of the galactic high energy gamma rays results mainly from the interaction of CR nuclei and electrons with the nuclei of the interstellar gas. An additional contribution is obtained from the interaction of CR electrons with the interstellar photons through the inverse-Compton (IC) process. Gamma ray astronomy therefore offers…
EXOSAT results on the X-ray burster 2S 1254-690.
Parmar, A. N.; Courvoisier, T. J. -L.; Peacock, T.
Exosat observations of 2S1254-690 in August 1984 have confirmed the presence of periodic dips in the X-ray intensity. These dips occurred with a period of 3.9 hours and lasted for about 50 minutes. During individual dips, the observed X-ray flux oscillated several times between the quiescent level and an undetectable level on time scales varying f…