Search Publications
Serendipitous EXOSAT sources in the region of the Coma cluster : active galactic nuclei with steep X-ray spectra.
Branduardi-Raymont, G.; Mason, K. O.; Martin, C. +1 more
A ≡7-hr observation of the central part of the Coma cluster of galaxies has been performed with the EXOSAT LE telescopes and CMA detectors. Five serendipitous sources are detected within the inner 35 arcmin radius of the field. Optical spectroscopy shows that four of these are background AGN not associated with the cluster. At the sensitivity leve…
Dwarf novae in outburst : simultaneous ultraviolet and optical observations of RU Pegasi and TZ Persei.
Verbunt, F.; Schwarzenberg-Czerny, A.; Jones, D. H. P. +6 more
The authors present ultraviolet and optical observations of the dwarf novae RU Peg and TZ Per during decline from outburst. In both systems the flux drops simultaneously at all wavelengths. In TZ Per the flux distributions during standstill and during the decline from different outbursts are similar. The authors discuss briefly the implications of…
IUE observations of RCB stars during extinction minima.
Evans, A.; Whittet, D. C. B.; Bode, M. F. +2 more
The R Coronae Borealis stars RY Sgr and MV Sgr have been observed with the long-wavelength (LWR) camera on the IUE satellite during deep extinction minima. The ultraviolet spectrum of RY Sgr showed a rich chromospheric spectrum, similar to that observed in the optical spectrum of this object during previous extinction episodes. Near-simultaneous o…
The ultraviolet variability of the BL Lacertae object OJ 287.
Coe, M. J.; Hanson, C. G.
The International Ultraviolet Explorer (IUE) satellite has been used to observe the BL Lacertae object, OJ287, at 26 epochs between 1978 May and 1984 May. These observations how large and often rapid variations in both the intensity and the spectral slope of the UV continuum. In general, the changes in intensity show little or no correlation with …
Upper limits to coronal line emission from X-ray detected T Tauri stars.
Penston, M. V.; Johnstone, R. M.; Lago, M. T. V. T.
High dispersion AAT spectrograms of the two T Tauri stars, GW Orionis and T Tauri, are used to set upper limits to the intensities of the coronal emission forbidden line of Fe XIV at 5303 A. Comparison made with the intensities of chromospheric and the transition-region emission lines, and of the X-ray flux, shows that in GW Ori the Fe XIV forbidd…
UV and optical observations of PG 1351+64, a bright Seyfert galaxy ORA low-luminosity QSO.
Tanzi, E. G.; Falomo, R.; Treves, A. +3 more
PG 1351+64 was repeatedly observed in 1979 - 83 with IUE. Variations of a factor of 2 in both line and continuum intensity were observed with a time-scale of ≡1 month. Coordinated optical observations suggest that the ultraviolet variability is not accompanied by optical variability, so that the overall energy distribution changes shape. The prope…
Shock-heated gas in the I Per OB association.
Nandy, K.; McLachlan, A.
In response to a suggestion by Phillips & Gondhalekar (1981) that hotgas is receding from the I Per OB association with a velocity of ≡30 km s-1, the authors have examined the IUE high-dispersion spectra of stars in the association for blueshifted lines of interstellar C IV, Si IV and Al III. As a result, the high-velocity ions are …
The identification of H 2311+77 with HD 220140, a probable RS CVn star.
White, N. E.; Giommi, P.; Pravdo, S. H.
H2311+77, one of the bright soft X-ray sources in the sky originally detected with HEAO 1, has been identified in an EXOSAT imaging observation with a 7.7-mag late-type star, HD 220140. The X-ray luminosity and the optical characteristics of this star indicate that it is probably an RS CVn binary system.
IUE high-resolution observations of Mira B.
Reimers, D.; Stickland, D. J.; Cassatella, A. +2 more
A high-resolution spectrum of Mira obtained with IUE on 1983 July 7 confirms the presence of broad emission lines with typical half base widths of ≅300 to roughly 1000 km s-1. No narrow emission lines are detected. The observed broad lines cannot originate from the extended atmosphere of the cool giant variable. The authors show in part…
IRAS observations of MKN 501 with quasi-simultaneous observations at radio, near-infrared and ultraviolet wavelengths.
Di Cocco, G.; Coe, M. J.; Spinoglio, L. +9 more
The authors present quasi-simultaneous observations at radio, far-infrared, near-infrared and ultraviolet wavelengths of the BL Lac object MKN 501. Specifically, they have observed the source with the IRAS satellite, and they show that the best power-law fit to the 12 to 100 µm data gives a slope of index α = 0.55±0.1. They show that the com…