Search Publications
Two New Bl-Lacertae Objects Discovered in the Error Boxes of Hard X-Ray Sources
Tagliaferri, G.; Beuermann, K.; Branduardi-Raymont, G. +6 more
Two new BL Lacertae objects, located within the error boxes of hard X-ray sources, have been discovered during a systematic program to identify a large sample of EXOSAT serendipitous sources. Both hard X-ray sources were detected during the HEAD 1 whole sky survey and have been associated to a Seyfert galaxy and to a Be star. The EXOSAT data are c…
Anomalously high intercombination line ratios in symbiotic stars; extreme Bowen pumping ?
Feibelman, W. A.; Bhatia, A. K.; Kastner, S. O.
International Ultraviolet Explorer observations of the ratio of the O III intercombination lines near 1660 A are assembled, showing that the observed ratios in symbiotic stars are significantly higher than the theoretically predicted optically thin limit of 2.5. The presence of an enhancing physical process is thereby indicated. It is suggested th…
The EXOSAT Spectral Survey of Bl-Lacertae Objects
Maccagni, D.; Tagliaferri, G.; Giommi, P. +3 more
The results of an analysis of the X-ray spectra of seventeen BL Lacertae objects measured in 66 observations are presented. The 0.1 - 10 keV spectra of these objects exhibit convex curvature in the log F - log plane. This curvature is intrinsic to the continuum . No evidence for high energy tails is found, at least below energies of 8 - 10 keV, no…
EXOSAT observations of the remnant of SN 1006.
Jones, L. R.; Pye, J. P.
The remnant produced by the supernova explosion of AD 1006 has been studied in X-rays with the Exosat Observatory. Images in the energy range 0.1-2 keV with resolution sufficient to resolve the limbs, obtained through three different filters, reveal a limb-brightened nebula containing clumps of emission and displaying large spectral variations wit…
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…