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PKS 2005-489 : a very bright BL Lac object in a nearby galaxy.
Wamsteker, W.; Warwick, R. S.; Pettini, M. +2 more
The galaxy identified with the flat-spectrum radio source PKS 2005-489 has a bright and variable stellar nucleus with a brightest observed V magnitude of ≡13. The authors report radio, optical, UV and X-ray observations which indicate variability and power-law continua in each of these wavebands, leading to the conclusion that PKS 2005-489 is one …
Optical and X-ray observations of 4U 2129+47/V1727 CYG in an extended quiescent state.
Pietsch, W.; Gottwald, M.; Graser, U. +1 more
Observations of the 5.h2 h X-ray binary 4U2129 + 47/V1727 Cyg for more than one orbital cycle on September 29 and October 4, 1983 with the ESA X-ray satellite EXOSAT failed to detect the source in the low and medium X-ray energy band. Quasi-simultaneous UBV photometry using the 2.2 m telescope at the German-Spanish Astronomical Center, …
Quasi-Periodic Oscillations in Low-Mass X-ray Binaries
van der Klis, M.
Strong, persistent, high-frequency QPO (quasi-periodic oscillations) have been discovered with EXOSAT in seven luminous, persistently bright low-mass X-ray binaries. The detailed properties of these QPO, in particular their dependence on source intensity, are discussed. A large variety is observed in the relations between source intensity and QPO …
Observations of Three BL Lacertae Objects: Constraints on Inhomogeneous Relativistically Beamed Jet Models
Bruhweiler, F. C.; Miller, H. R.; Worrall, D. M. +4 more
Multifrequency observations are presented of three BL Lac objects, including the first UV measurements of 0912 + 297 and 1219 + 285. An eight day optical flare was measured from 0422 = 004 in which a doubling in visual flux density was noted; other sources displayed smaller daily fluctuations. The 5-15 GHz radio flux from these three objects remai…
Ultraviolet spectra of quasars in the redshift interval 0.3 to 2.0.
Wilson, R.; Gondhalekar, P. M.; Obrien, P.
UV spectroscopic observations of nine QSOs with z = 0.3-2.0, obtained with the IUE SWP and LWR(P) instruments during 1978-1983, are reported. The continuum emission is attributed to the combination of a 20,000-30,000-K blackbody (the source of most of the UV emission), Balmer emission, and a power-law component (extending to the X-ray emission). T…
EXOSAT and IUE Observations of Contact Binaries
Heise, J.; Vilhu, O.
EXOSAT observations are reported of the contact binaries W UMa, VW Cep, 44t Boo, XY Leo, and V566 Oph and the detached short-period RS CVn stars ER Vul and HD 209943. Complete X-ray light curves were obtained for W UMa, VW Cep and 44t Boo. Nearly simultaneous IUE observations of VW Cep provide important comparisons of the Mg II emission, the UV co…
Measurement of the EUV Spectrum of the Hot White Dwarf Feige 24
Heise, J.; Bleeker, J. A. M.; Brinkman, A. C. +1 more
A high-resolution EUV spectrum of the hot white dwarf Feige 24 in the 190-350 A range is presented. It is demonstrated that, in this region, the measured spectrum deviates strongly from energy distributions calculated from LTE homogeneous model atmospheres for hot DA white dwarfs. The data cannot be fitted with a pure hydrogen spectrum nor with a …
Observations of the Bowen Fluorescent Mechanism in Planetary Nebulae
Aller, L. H.; Likkel, L.
Measurements of Bowen fluoresecent lines in 17 planetary nebulae are presented and the relative line strength is composed with theory. There is generally good agreement with the line intensities expected by Saraph and Seaton (1980). The largest deviation from theory is in the O III I(3429A/I3444A) ratio, which is consistently lower than predicted.…
Detection of Scattering in the 2175 Angstrom Interstellar Band
Bohlin, R. C.; Witt, A. N.; Stecher, T. P.
Spectrophotometric observations of two reflection nebulae and their illuminating stars obtained with the International Ultraviolet Explorer Satellite have provided the first evidence for the presence of a scattering contribution to the 2175 A interstellar extinction band. Lower than normal far-UV extinction for the stars embedded in the nebulae in…
Variability of Lyman-Alpha and the Ultraviolet Continuum of 3C 446
Huggins, P. J.; Kinney, A. L.; Bregman, J. N. +1 more
IUE observations have been conducted over the 1230-3175 A range for the violently variable quasar 3C 446, beginning in June 1980, at intervals of 1.2, 2.2, 0.5, and 0.4 yr. Strong absorption of the continuum was found below 1830 A, probably corresponding to a Lyman edge at z of 1.00 + or - 0.01. The absence of Mg II 2798 A absorption implies that …