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LMC X-2 : an extragalactic bulge-type source.
Parmar, A. N.; Motch, C.; Beuermann, K. +3 more
The X-ray source LMC X-2 was observed with EXOSAT for ~8 h on February 2, 1984 with simultaneous photometric and spectroscopic optical coverage. The source was seen at a luminosity of L_x_ ~1.5 10^38^ erg s^-1^ with a mean X-ray spectrum can be described equally well by either the superposition of thermal emission from an optically thin (T_th_ ~5 …
Small-Amplitude Coherent Signals in the X-Ray Emission of NGC 4151
Piro, L.; Perola, G. C.; Fiore, F. +1 more
We present the results of the temporal analysis performed on four EXOSAT medium-energy observations of the Seyfert galaxy NGC 4151, selected for their long duration and background stability. The light curves can be adequately described in terms of regular trends (representing variations on time scales >= 1 day) to which small-amplitude fluctuat…
X-Ray Bursts from 4U 1705-44: Another Case of Burst Properties Dependent on the Strength of the Persistent Emission
Haberl, F.; van Paradijs, J.; Lewin, W. H. G. +3 more
Three Exosat observations are reported of the low-mass X-ray binary 4U 1705-44 during which X-ray bursts are detected. Seventeen bursts are recorded in the low-intensity state and seven bursts in the medium-intensity state, of which 22 are suitable for a detailed analysis. Correlations between the burst properties and the strength of the persisten…
Broad emission line variability in 3C 273.
Zheng, W.; Wilson, R.; O'Brien, P. T.
We find that the broad Ly α H{BETA} and Fe II emission lines in the luminosity quasar 3C 273 vary by 10-30 per cent on time-scales less than a year. All the line variations occurred during approximately the same period. The line cores vary more than the wings, indicating that the line variability involves only pan of the BLR. The line variability …
Carbon abundance in the primaries of six Algol-type stars.
Cugier, H.
The abundance analysis of carbon in six Algol-type stars was performed using IUE archival data. In order to interpret the observed spectra, both LTE and non-LTE line profiles are computed. A cosmic abundance of carbon is obtained, log N(C/H) = - 3.48, in the primary components of Delta Librae, U Sagittae, RS Vulpeculae and u Herculis. All these sy…
The 2.8-hour flux modulation of the cataclysmic variable PG 1711+336.
Branduardi-Raymont, G.; Mason, K. O.; Rosen, S. R. +1 more
High-speed optical photometry of the cataclysmic variable PG1711 + 336 is used to confirm the presence of a 2.8-hour periodic modulation in the light curve of the star and to improve its ephemeris. Pronounced flickering on time-scales between 10 and 20 minutes is found superimposed on the 2.8-hour variation. Three hours of time-resolved spectrosco…
Astrophysical contributions of the International Ultraviolet Explorer.
Kondo, Yoji; Maran, Stephen P.; Boggess, Albert
The International Ultraviolet Explorer (IUE) was launched on Janurary 26, 1978. The mission was conceived from the beginning as an ultraviolet spectroscopic observatory that could be used by astronomers as they were accustomed to observing from the ground, without special training in orbital operations. The authors describe some highlights of the …
The High-Resolution Spectrum of the Pulsating, Pre-White Dwarf Star PG 1159-035 (GW Vir)
Husfeld, D.; Sion, E. M.; Wesemael, F. +3 more
High-resolution and low-resolution UV spectra and a high-resolution optical spectrum were obtained for PG 1159-035, revealing apparent photospheric absorption features with defined cores from N V 1240 A, N IV 1270 A, O V 1371 A, and C IV 1550 A. The photospheric velocity derived using all of these lines except for C IV is about +35 km/s. Equivalen…
X-Ray, Ultraviolet, and Optical Observations of the Intermediate Polar FO Aquarii (H2215-086)
Mukai, K.; Maraschi, L.; Tanzi, E. G. +9 more
An extensive set of quasi-simultaneous, multiwavelength observations of the intermediate polar FO Aqr (H2215-086) obtained in 1983-1985 with the Exosat and IUE satellites and from La Palma Observatory are presented. The rotational 21 minute period and sideband periods due to beating with the orbital modulation are observed in the optical band and …
Ultraviolet Extinction Differences within NGC 6530
Bohm-Vitense, Erika; Boggs, Don
Ultraviolet extinction curves are presented for 14 stars in the very young cluster NGC 6530. The variation of the short-wavelength extinction is consistent with that expected based on random errors alone, although the weakest extinction is found only toward the cluster center. Variations significantly larger than the measurement uncertainty are fo…