Search Publications
Flaring and quiescent X-rays from Castor.
Schmitt, J. H. M. M.; Tagliaferri, G.; Pallavicini, R. +2 more
Using data obtained with the Low Energy (LE) and Medium Energy instruments aboard Exosat, the first detection of both flaring and quiescent X-ray emission from the A-type visual binary Castor (alpha Gem) is reported. In the LE, Castor was clearly resolved from the nearby star YY Gem, which was also observed to flare some hours after Castor. After …
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…
EXOSAT observation of the supernova remnant MSH 15-52.
Hasinger, G.; Aschenbach, B.; Brinkmann, W. +3 more
The results of an Exosat observation of the supernova remnant MSH 15-52 and of the pulsar PSR 1509-58 are presented and discussed. In the energy range 1.6-11 keV, the radiation flux of the nebula surrounding the pulsar detected by the ME instrument has been fitted with a power law spectrum with index alpha about 1.86 (photon spectrum) and column d…
The nucleus of Abell 35 : a cataclysmic binary ?
Jasniewicz, G.; Acker, A.
Simultaneous photometric and spectroscopic observations of the visible central star BD - 22 deg 3467 of the large planetary nebula Abell 35 are reported. This fast rotating star has a spectral type G8IV, and shows a double peaked emission line at H-alpha, varying with a period identical to the photometric one, equal to 0.7653 days. Both the maximu…
Discovery of a highly ionized, low mass-loss wind and a corona seen in absorption in the G9 II star HR 6902.
Reimers, D.; Baade, R.; Schroeder, K. -P.
IUE observations of HR 6902 (G9II + B9V) 1 and 2 days before and during total eclipse of the B star are discussed. The G bright giant has a highly ionized, hot (Te = 87,000 K) wind seen as C IV, Si IV, and C II resonance-line scattering of B-star photons during totality, with a mass-loss rate of 2 x 10 to the -11th solar mass/yr (+ or - factor 3).…
UV observations of Herbig-Haro objects associated with bipolar molecular outflows : HH 7, HH 11 and HH 29.
Liseau, R.; Cameron, M.
Results are presented of IUE observations of three shock excited visible Herbig-Haro nebulae: HH7, HH 11, and HH 29. With the possible exception of HH 11, large deviations were found from the 2 2S-1 2S two-photon decay continuum of atomic hydrogen. It was also found that the continuum of HH 29 varies considerably in both the intensity and the spec…
The ultraviolet and optical spectrum and evolutionary status of HD 62910 (WN 6-C 4).
Willis, A. J.; Stickland, D. J.
A detailed study is presented of the combined UV-optical spectroscopy for the WN-C composite spectrum star HD62910. A reddening of E(B-V) = 0.80 + or - 0.05 is derived along with an intrinsic UV-optical continuum energy distribution fitted by a blackbody at about 30,000 K. The composite subtypes are confirmed as WN6 and WC4. The linewidths of both…
BD +37 1160 : a probable optical counterpart of the X-ray source 1H 0521+373.
Rossi, C.; Giovannelli, F.; Kurt, V. G. +13 more
Results are reported on detailed X-ray, UV, optical, and IR observations of two stars: BD + 37 deg 1146 and BD + 37 deg 1160. These data suggest that the star BD 37 deg 1160 is the optical counterpart of the X-ray source 1H 0516 + 373. It is shown that the optical spectrum of this star displays rapidly variable emision features, an IR excess emiss…
A study of ultraviolet spectra of zeta Aurigae/VV Cephei systems. XII. The physical state of supergiant chromospheres at the transition from coronae to cool winds.
Schroeder, K. -P.
Results are reported from an analysis of 20 IUE spectra of the Zeta Aur binaries HR 6902, HR 2554, and Tau Per during their near-eclipse phases in 1987-1988. The data are presented in tables and graphs and characterized in detail, with comparison of similar results for 22 Vul. It is shown (1) that the Fe II column densities at low heights (about 1…