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Simultaneous EXOSAT and IUE Observations of Fairall 9: Short and Long-Term Variability
Piro, L.; Perola, G. C.; Boksenberg, A. +11 more
Simultaneous observations of the Seyfert I galaxy Fairall 9 (F9) were performed with Exosat and IUE during October 1983 and 1984. A decrease in the flux of the source by more than a factor of 2 was observed at all wavelengths between the two epochs. Furthermore, in the X-ray (0.05-10-keV) band, variability of the order of 50 percent on a time scal…
Spectrophotometry of the eclipsing dwarf nova V2051 Ophiuchi.
Watts, D. J.; Bailey, J.; Hill, P. W. +3 more
A detailed phase-dependent spectroscopic study of the eclipsing dwarf nova V2051 Oph is reported. The spectroscopic observations were carried out in the optical and UV wavelengths using the 3.9-meter Anglo-Australian Telescope (AAT) International Ultraviolet Explorer (IUE) spacecraft. The optical spectrum shows strong Balmer emission, as well as w…
The ultraviolet to infrared continuum of ten narrow emission line active galaxies.
Boisson, C.; Durret, F.
The overall continuum spectra of 10 narrow line active galaxies are presented based on IR ground-based and IRAS photometry, long slit optical spectrophotometry and UV spectroscopy obtained with the IUE. Nonstellar components found include a nonthermal power law continuum in the optical, a thermal UV component from an accretion disk, Balmer continu…
A unique triple-peaked type-1 X-ray burst from 4U/MXB 1636-53.
van Paradijs, J.; van der Klis, M.; Lewin, W. H. G. +3 more
The authors report the detection, with EXOSAT, of an X-ray burst from 4U/MXB 1636-53, whose intensity profile shows three distinct peaks. A time-resolved spectral analysis of this burst shows that this triple-peaked profile, which is clearly visible in the bolometric flux variations, is not the result of a major radius expansion of the neutron sta…
The Ionization Structure of Planetary Nebulae. VI. NGC 7662
Barker, T.
Spectrophotometric observations of emission-line intensities over the spectral range 1400 - 7200 Å have been made in five positions in the planetary nebula NGC 7662. The variation of the Balmer decrement with position in the nebula suggests that there may be internal dust. The O++ and Balmer continuum electron temperatures decrease with…
NLTE-analysis of the sdO star ROB 162 in the globular cluster NGC 6397.
Heber, U.; Kudritzki, R. P.
A high-resolution visual blue spectrum of the subluminous O star ROB 162 in the globular cluster NGC 6397 has been analysed for its atmospheric parameters by means of NLTE model atmospheres. The effective temperature Teff = 51000±2000K, the gravity log g = 4.5±0.2 and a normal helium mass fraction (Y = 0.28 (+0.04, -0.06)) resulted. Spe…
The Abundance of Gallium in B-Type Chemically Peculiar Stars
Sadakane, K.; Jugaku, J.; Takada-Hidai, M.
Quantitative analyses of the Ga abundances in 27 Hg-Mn stars, 11 Si (magnetic) stars, eight He-weak stars, and seven normal stars are made with the resonance lines of Ga II at 1414 A and Ga III at 1495 A in International Ultraviolet Explorer (IUE) spectra. The Ga overabundances are confirmed as a genuine anomaly in many peculiar stars. Only upper …
Ultraviolet and Infrared Observations of Stars with ``Quenched'' Chromospheres and the Nature of Mass Loss
Carpenter, K. G.; Stencel, R. E.; Hagen, W.
Previous observational evidence implies that the presence of Ca II emission, a chromospheric indicator, is correlated with the gas/dust ratio in the envelopes of red giant and supergiant stars. An attempt is made to determine whether this correlation can be generalized to all chromospheric activity indicators and the gas/dust ratio. New ultraviole…
Bootstrap sampling - Applications in gamma-ray astronomy
Mayer-Hasselwander, H.; Simpson, G.
Techniques for using bootstrap sampling (BS) methods to analyze cosmic gamma ray data are described. Sophisticated statistical techniques are required for gamma ray analyses because of the rarity of available data, i.e., only about 200,000 photons in the energy range 50-5000 MeV have been recorded to date. BS consists basically of randomly samplin…
Abundances in the planetary nebula BD +30 3639.
Pottasch, S. R.; Pwa, T. H.; Mo, J. E.
High resolution IUE spectra of the low excitation nebula BD +30°3639 show absorption lines of nebular material and of the intervening ISM. With the method described in Pwa et al. (1984) ionic abundances were derived for Mg0, Mn+, Fe+, Zn+ (all for the first time in a PN) and for Mg+, Al+<…