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The Accretion Wake of 31 Cygni
Ahmad, I. A.
Archival IUE observations of 31 Cygni at phases at which its sister Zeta Aurigae systems exhibit evidence of an accretion wake are discussed. The absence of absorption in Mg II can be explained by the phase at the specific times of observation. The detection of high-velocity absorption due to C IV but not N V implies a shock temperature lower than…
Gamma-Ray Emission in MeV--GeV Region from Cygnus X-3
Li, Ti-Pei; Wu, Mei
The analysis of the simultaneous X-ray and gamma-ray observations of Cygnus X-3 by the ESA satellite COS B indicates that there exists a negative correlation between intensities of 2-12 keV X-rays and 150-5000 MeV gamma rays of Cygnus X-3. A clear image of a gamma-ray source at the position of Cygnus X-3 is obtained from the spatial distribution o…
Heavy elements in the 2000-3000 A range of four AP stars.
Faraggiana, R.
The long wavelength range of IUE has been examined in a search for heavy elements in four chemically peculiar stars of CP2 subgroup. Pb II 2203.53 appears to be present and a lead abundance higher than the solar one is derived for HD 188041 and HD 201601. No firm indication of the presence of Th II and U II can be established in the four program s…
The region of formation of the ultraviolet high temperature resonancelines in the eclipsing binary beta Persei (Algol).
Sahade, J.; Kondo, Y.; Brandi, E. +1 more
A new series of IUE observations of Beta Persei has shown that the high temperature resonance lines of Si IV and C IV arise in a region that surrounds the brighter, early-type component of the system. The continuum spectrum corresponds to that of a B8V object, and the value of E(B-V) that yielded the best match between the two IUE regions was 0.06…
The presence of carbon in DZ star atmospheres.
Koester, D.; Weidemann, V.
A recently obtained SWP spectrum of the DZ star L 119-34 is presented. The spectrum clearly shows the presence of C I lines. This result suggests that carbon is always present in cool helium-rich white dwarf atmospheres, independent of optically based spectral classification.
The Ultraviolet Variability of HD 45166 (qWR+B8 V): Evidence for Stellar Wind Radiative Instabilities
Stickland, D. J.; Howarth, Ian D.; Heap, S. R. +1 more
High-resolution IUE spectroscopy of the low-mass qWR star HD 45166, obtained at several epochs during 1980-1988, reveals a complex pattern of variability in its stellar wind emission lines, P Cygni profiles, and highly ionized photospheric absorption spectrum. The most intensive observations, obtained during a 36 hr continuous run in February 1988…
The Ultraviolet to Infrared Energy Distribution of the BL Lacertae Object PKS 0422+00 at Two Different Brightness Levels
Maraschi, L.; Tanzi, E. G.; Bouchet, P. +2 more
The BL Lacertae object PKS 0422+00 was observed with IUE (International Ultraviolet Explorer) on 1987 August 31-September 1, when the visual magnitude of the object was V = 16.2, and again ~ 4 months later (1988 Jan 10) during an active state (V = 15.6). Quasi-simultaneous optical to infrared observations allow deriving a detailed spectral flux di…
A comparative study of the discrete and cross correlation techniques : an application to the NGC 5548 IUE light-curve.
Clavel, J.; Rodriguez-Pascual, P. M.; Santos-Lleo, M.
Over the past few years, cross-correlation techniques have become of increasing importance in the context of active galactic nuclei (AGN) variability studies. Inference of time delays in the response of the emission line intensities with changes in the ionizing continuum flux have the potential to yield the length scale of the broad line emitting …
Activity in late-type stars. IV. The 1980 August 20 flare on proxima Centauri revisited.
Byrne, P. B.; McKay, D.
This paper presents a reanalysis of simultaneous ultraviolet and soft X-ray observations of a flare on the dMe star, Proxima Centauri. Using an emission measure analysis, as well as density sensitive line ratios, the electron density and the total emitting volume of the flare plasma which is at midtransition region temperatures are derived. These,…
The EXOSAT view of the north and east Cygnus loop.
Ballet, J.; Rothenflug, R.
EXOSAT images of the northeast third of the Cygnus Loop are presented. The brightest parts are analyzed and the different filters on the CMA are used to put constraints on the temperature. This is especially valuable for the warm gas, for which temperatures as low as 1.4 x 10 to the 6th K in the east are estimated. The spectra obtained with EXOSAT…