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The peculiar UV and optical spectrum of the LMC supergiant HD 269216.
Prinja, R. K.; Schild, H.
Low resolution IUE UV and optical observations are presented of HD 269216, the visually brightest member of the LH 39 association in the LMC. Although the UV and optical line spectra are broadly consistent with a B 8 Ia spectral type for HD 269216, the classification is complicated by several discrepancies. The observed UV continuum flux distribut…
The Ultraviolet Spectrum of KX Trianguli Australis
Feibelman, Walter A.
Low-dispersion and high-dispersion IUE satellite observations of the symbiotic star KX TrA, carried out on May 7, 1990, are reported. The low-dispersion data show no significant changes from the observation data obtained a decade ago. Resonantly excited high-excitation Fe II emission lines are seen in the UV spectra of KX TrA, suggesting the exist…
Leptonic origin of diffuse galactic high-energy gamma rays - Indications for a varying cosmic ray proton-to-electron ratio
Schlickeiser, R.; Pohl, M.
The flux of high-energy (more than 300 MeV) gamma rays - caused by nonthermal bremsstrahlung and inverse Compton scattering - and the synchrotron flux at 408 MHz are calculated with the same power-law spectrum of relativistic electrons. Both are compared with the values observed at higher latitudes in the anticenter direction by employing the COS-…
Cometary plasma processes
Johnstone, Alan D.
The present conference on cometary plasma processes encompasses cometary analogies of solar-wind interactions with planets, cometary plasma observations and simulations, disconnection events in Comet Halley, the spectrum and energy of solar-wind turbulence related to comets, and observations of the velocity distributions of pickup ions and ion flu…
Detection of a stellar flare at extreme ultraviolet wavelengths
Bromage, G. E.; Barstow, M. A.; González-Riestra, R. +3 more
THE transition region between stellar chromospheres and coronae contains plasma at temperatures of 105-106 K, radiating predominantly at extreme ultraviolet (EUV) wavelengths (60-1,000 Å 0.012-0.2 keV). To understand the energy transport processes that maintain the corona, radiative losses from this region must be studied, pa…
X-Ray Luminosity and Spectral Variability in the Seyfert Type I Galaxy: PG 2130+099
Singh, K. P.; Rao, A. R.; Vahia, M. N.
We present broad-band (0.1-10 keV) X-ray observations of a bright Seyfert I galaxy, PG 2130+099, using the low-energy (LE) and the medium-energy (ME) detectors of the EXOSAT Observatory. The observations were carried out on two occasions separated by a year (in 1984 and 1985), and the X-ray flux was found to have increased by ~35% in the 1.5-6 keV…
Plasma parameters near the comet Halley bow shock
Coates, A. J.; Neubauer, F. M.; Rème, H. +5 more
We analyse the available plasma data from the JPA, MAG and RPA instruments on Giotto for the inbound bow shock crossing at comet Halley. Proton, cometary heavy ion, electron and magnetic field data are combined on the inbound pass to yield the pressures of all the plasma components, and hence the characteristic plasma speeds and the Mach number of…
Tautenburg proper motion fields
Scholz, R. -D.; Hirte, S.
The possible use of Tautenburg Schmidt plates to determine proper motions was analyzed using the new data base of the Tautenburg plate archive. All fields with at least four first epoch plates were included along with the 10 Hipparcos-Tautenburg link fields and the 17 fields in the program of the main meridional section of the Galaxy. The distribu…
Speckle interferometry of HIPPARCOS link stars - III.
White, G. L.; Argue, A. N.; Reynolds, J. E. +5 more
A third list of stars is presented which have been tested by speckle interferometry for use in the Hubble Space Telescope link between the Hipparcos astrometric reference frame and the extragalactic VLBI reference frame. Structural information on angular scales of 0.15-1.2 arcsec for 34 Southern Hemisphere stars is reported from observations made …
Pollution of P Cygni profiles by Fe IV and FeV photospheric absorption inthe ultraviolet spectrum of O-type stars.
Surdej, J.; Nemry, F.; Hernaiz, A.
It is reported that the main pollution in the spectral ranges 1270-1500 and 1500-1860 A is caused by photospheric absorption lines of FeV and FeIV, respectively. Making use of the first order moment W1 of a P Cygni line profile, it is shown that the effect of this photospheric pollution may lead to systematic errors, exceeding typically 50 percent…