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IUE-ULDA/USSP - The on-line low resolution spectral data archive of the International Ultraviolet Explorer
Pasian, F.; Talavera, A.; Wamsteker, W. +8 more
The on-line IUE Uniform Low Dispersion Archive (ULDA) and the associated ULDA Support Software Package (USSP) are described. The underlying philosophy, the detailed corrections made to the data and the implementation details are summarized. The low-resolution data are made available for direct access to the astronomical community through the exist…
Evidence for a Cool Wind from the K2 Dwarf in the Detached Binary V471 Tauri
Carpenter, K. G.; Mullan, D. J.; Bruhweiler, F. C. +1 more
Evidence for mass loss from the K2 dwarf in V471 Tauri is found in the form of discrete absorption features in lines of various elements (Mg, Fe, Cr, Mn) and ionization stages (Mg I, Mg II, Fe I, Fe II). Resonant Mg II absorption indicates a mass loss rate of at least 10 to the -11th solar masses per year. The wind appears to be cool (no more than…
Rotational modulation and flares on RS Canum Venaticorum and BY Draconis.stars. X. The 1981 October 3 flare on V711 Tauri (= HR 1099).
Linsky, J. L.; Simon, T.; Neff, J. E. +5 more
We present a unique set of high resolution spectra of V71 1 Tauri = HR 1099 (G5 V + K1 IV) obtained with both the SWP and LWR cameras of lUE, together with simultaneous 6.4 GHz microwave emission and optical photometry, during a bright flare on 3 October 1981. The electron density of the flaring plasma at 6 104K was about 11011
The Active Chromosphere Binary HD 17433 (VY Arietis)
Saar, Steven H.; Barden, Samuel C.; Bopp, Bernard W. +4 more
The sixth-magnitude K star HD 17433 (VY Ari) is shown to be an active-chromosphere binary with an orbital period of 13.198 days. A photometric (rotational) period of 17.4 days is indicated by the existing photometry, implying that HD 17433 is not in synchronous rotation. In the optical, H-alpha is seen in emission, with variable profile and intens…
The absolute magnitudes of RR Lyrae stars - I. X Arietis.
Jameson, R. F.; Fernley, J. A.; Kilkenny, D. +4 more
A Baade-Wesselink analysis based on the infrared flux method of Blackwell and Shallis (1977) is used to estimate the temperature and angular diameter of X Ari at all phases of the pulsational cycle. These results are then used to determine the radius, distance, and absolute magnitude. New UV, optical and IR observations for this metal-poor star ar…
Ultraviolet flares on II Pegasi.
Doyle, J. G.; Byrne, P. B.; van den Oord, G. H. J.
UV spectroscopic observations of the RS CVn star, II Peg, were obtained in February 1983. The observations show evidence for flare activity in greatly enhanced chromospheric and transition region emission lines. The flare radiation is isolated and the electron pressures of the mean quiescent atmosphere and the two flares are derived from the inter…
Can the EXOSAT Observations of DA White Dwarfs Be Explained by Layered Atmospheric Structures?
Koester, D.
It is demonstrated that the Exosat broadband filter observations of DA white dwarfs, which have recently been interpreted with homogeneously mixed H/He atmospheres (Jordan et al, 1987; Paerels and Heise, 1989), can be explained with stratified theoretical models. In these models a very thin H layer is floating on top of the underlying He. The tran…
The X-Ray Structure of Centaurus A from 0.1 to 50 keV Observations with EXOSAT
Morini, Marco; Anselmo, Franco; Molteni, Diego
We present the results from four EXOSAT observations of the radio galaxy Centaurus A performed during 1984-1985. Data have been obtained both in the low-energy (< 2 keV) and in the medium-energy (2-50 keV) X-ray energy bands. The emission from the nucleus of the galaxy detected in the medium-energy X-ray band exhibits time variability on all ti…
Intrinsic Ultraviolet (912--3200 Angstrom ) Energy Distribution of OB Stars
Longo, Renata; Stalio, Roberto; Polidan, Ronald S. +1 more
Low-dispersion 500-3200-A spectra of 20 OB stars are used to derive three individual extinction curves in the wavelength range 912-1200 A. The dependence of the intrinsic UV fluxes of OB stars on both spectral type and luminosity is demonstrated. UV color indices are proposed. The results confirm the previous finding that O star spectra are not si…
Analysis of suprathermal electron properties at the magnetic pile-up boundary of comet P/Halley
Anderson, K. A.; Neubauer, F. M.; Rème, H. +10 more
Among the plasma discontinuities detected by the GIOTTO spacecraft around comet P/Halley, the Magnetic Pile-up Boundary, located at about 135,000 km from the nucleus, has a sharpness which was not foreseen by theoretical models. At this boundary, which marks the beginning of the region where the field lines draped around the nucleus have been pile…