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The ultraviolet spectra of active galaxies with weak optical Fe II lines.
Netzer, H.; Wamsteker, W.; Wills, B. J. +1 more
The authors have obtained simultaneous optical and IUE spectra of two Seyfert galaxies that show very weak optical Fe II lines: Mrk 290 and Mrk 915. IUE archival spectra of the radio galaxy 3C 390.3 are also compared with optical data obtained during the same year. Strong, distinct ultraviolet features are observed in the spectrum of Mrk 290. A fi…
UV and optical spectroscopy of OB stars in M 31 and M 33.
Bianchi, L.; Hutchings, J. B.; Massey, P.
IUE UV spectra and MMT blue spectra have been obtained for 'normal' OB supergiant stars in M31 and M33. The authors classify the stars as late O to early B. UV and visible fluxes yield consistent values for the effective temperature, bolometric magnitudes, and extinction for the stars. The UV resonance lines have very low outflow velocities compar…
Large Magellanic CLOUD-X-4 AO:538-66 and Surrounding X-Ray Sources Observed with EXOSAT
Pietsch, W.; Beuermann, K.; Pakull, M. +4 more
Repeated observations of LMC X-4 with EXOSAT were carried out in 1983/84 in order to study its 30.5 day cycle and to cover the expected outbursts of the recurrent LMC transient A0538-66. The latter source was inactive during our campaign although a variable circumstellar envelope was still present around the optical counterpart. At least ten furth…
Rotational modulation of chromospheric emission in cool giants and "hybrid" stars.
Stencel, R. E.; Mullan, D. J.; Brosius, J. W.
Archival data from the International Ultraviolet Explorer have been used to study temporal variations of the Mg II h and k emission lines in eight late-type giants. Evidence is presented that the variations are periodic in nature. It is argued that the periodicities can be interpreted in terms of rotation. It is found that the four fastest rotator…
Photometric variations of the irregular variable V348 Sgr.
Jones, D. H. P.; Manfroid, J.; Heck, A. +2 more
The authors report visual estimates and photometric observations in various wavelength ranges of the irregular variable V348 Sgr. They cover dramatic drops of brightness (from V ≈ 12.5 to ≈ 18) which occurred in 1972, 1973 and 1981 with a time scale much shorter than the characteristic time mentioned by previous observers. These deep minima are, t…
Ss-Cygni in Outburst and Quiescence
Heise, J.; King, A. R.; Watson, M. G.
EXOSAT has been used to carry out a series of observations of the dwarf nova SS Cygni covering both quiescent and outburst states which provide a detailed picture of its behaviour at X-ray wavelengths. These results provide strong support for a new coronal model for the X-ray emission from non-magnetic white dwarf systems.
Multifrequency observations of the BL Lacertae object PKS 0537-441.
Maraschi, L.; Tanzi, E. G.; Treves, A. +1 more
PKS 0537 - 441 was repeatedly observed in the UV band with the International Ultraviolet Explorer and in the X-ray with the Einstein Observatory. On September 27, 1980, simultaneous observations in the two bands were obtained. Near-infrared photometry preceding and following the simultaneous observations by about one month is available from the li…
Temporal variations in UV spectra of the red giant C star, TW Hor.
Querci, M.; Querci, F.
The time behavior of ultraviolet emission lines in the cool carbon star TW Hor is discussed. The emission lines were obtained over a three year period using the International Ultraviolet Explorer (IUE) spacecraft in the wavelength range 2100-3300 A. All the lines are found to vary in time (on scales of about one hour to two months) without any app…
Spectroscopy and spectrophotometry of the nova-like system V3885 Sagittarii.
Drechsel, H.; Haug, K.
New optical and UV observations of the novalike variable V3885Sgr are analyzed. The line identifications and radial velocity measurements are presented, and the Balmer, He I, and He II line profiles are investigated. Physical parameters of the system are derived, and spectrophotometric light curves are presented. The continuum flux distribution be…
EXOSAT Medium-Energy Observations of CYGNUS-X-2
Pietsch, W.; Hasinger, G.; Sztajno, M. +1 more
On July 5. 6. 1983, during the EXOSAT performance verification (PV) and calibration phase, a raster scan of Cygnus X-2 was performed. In contrast to the previously observed smooth intensity variations on timescales of hours, the source revealed a behaviour unknown until now: active periods with high energy flares recurring on time scales of 300 50…