Search Publications
The Outer Atmospheres of the Coolest M Giants: Ultraviolet Spectra of rho Persei, 2 Centauri, G Herculis, theta Apodis, and R Lyrae
Johnson, Hollis R.; Eaton, Joel A.
High-dispersion IUE spectra of five M giants (spectral type M4 - M7) are discussed. Most of the emission lines and stronger absorption lines are identified for ρ Per in the wavelength range λλ2320 - 3030. The chromospheric spectra of ρ Per, R Lyr, 2 Cen, and g Her are remarkably similar, both among themselves and with respect to stars of earlier s…
Observations of the Late Superhump in VW Hydri
Motch, C.; Beuermann, K.; van Paradijs, J. +2 more
This paper presents the results of simultaneous optical and near-IR photometry, optical fast spectroscopy, and Exosat X-ray observations of the dwarf nova VW Hyi, obtained simultaneously during three consecutive orbital cycles, approximately two days after the 1983 November superoutburst terminated. The optical data show clear evidence for a 'late…
The excitation of SI emission lines in chromospheres of late-type giant stars.
Judge, P. G.
Constraints on the structure of the chromospheres of Alpha Boo, Alpha Tau, and Beta Gru derived from high-resolution IUE spectra are used to investigate the excitation mechanisms of emission lines of neutral sulfur, which are prominent in IUE spectra of late-type giant and supergiant stars. Observational data for the S I lines from other studies a…
Variations of the ultraviolet spectrum of 3C 273 : 9 years of IUE data.
Wamsteker, W.; Ulrich, M. -H.; Courvoisier, T. J. -L.
The quasar 3C 273 has been observed with the IUE satellite in the range 1200-3000 A every two weeks from 29 November 1986 to 18 February 1987, with additional observations in May 1986 and 1 June and 17 July 1987. These recent observations are analyzed together with the archived IUE spectra from 1978 to 1985. The flux at 1275 A undergoes variations…
Eight Years of Ultraviolet Spectra of the Variable BL Lacertae Object PKS 2155-305
Kondo, Y.; Urry, C. M.; Hackney, K. R. H. +1 more
The brightest known BL Lacertae object at ultraviolet wavelengths is PKS 2155-304, which was discovered as a result of its strong X-ray emission. Since 1979, 64 ultraviolet spectra of this object have been obtained with the International Ultraviolet Explorer (IUE) satellite. These have been analyzed in a consistent fashion using Gaussian extractio…
The C IV Doublet Ratio Intensity Effect in Symbiotic Stars
Altamore, A.; Kafatos, M.; Michalitsianos, A. G. +3 more
High-resolution UV spectra in the 1200-2000 wavelength range of the symbiotic variable R Aqr and its nebular jet were obtained in July 1987 with the IUE. The line profile structure of the C IV 1548, 1550 doublet in the jet indicates multicomponent velocity structure from an optically thin emitting gas. The C IV doublet profiles in the compact H II…
The High-Resolution Photospheric Soft X-Ray Spectrum of Sirius B
Heise, J.; Bleeker, J. A. M.; Brinkman, A. C. +1 more
The authors present the high-resolution soft X-ray spectrum of the hot white dwarf Sirius B, as measured with the 500 lines mm-1 transmission grating spectrometer on EXOSAT. The X-rays are of purely photospheric origin. Using a large grid of model atmospheres, the authors determine the effective temperature of Sirius B with high accurac…
Simultaneous EXOSAT and VLA Observations of the Contact Binaries VW Cephei and XY Leonis: Quiescent Emission and a Flare on VW Cephei
Heise, John; Vilhu, Osmi; Caillault, Jean-Pierre
Two W UMa-type contact binaries, XY Leo and VW Cep, were observed simultaneously with Exosat, the VLA, and, in the case of XY Leo, optically. The temporal coverage of each star was sufficient to monitor them throughout two orbital revolutions (P about 0.27 days); however, no orbital modulation of either the X-ray or 6 cm data was seen for either s…
Flare activity on UV Ceti : visible and IUE observations.
Bromage, G. E.; Dufton, P. L.; Keenan, F. P. +2 more
Simultaneous far-ultraviolet (IUE) spectroscopy and optical photometry and spectrophotometry of a flare on UV Ceti are reported. The flare reached ΔU = 2 mag but showed only modest enhancements in the IUE spectra. The optical spectrophotometry indicated broadened Balmer line profiles during the flare, with Hβ and Hγ clearly showing red wings (≡100…
The ultraviolet continuum of quasars -II. Continuum variability.
Wilson, R.; Gondhalekar, P. M.; O'Brien, P. T.
We present data on the variability of the ultraviolet continuum for a large sample of quasars observed with IUE. No variability was found on time- scales of days, but is common on time-scales of weeks to months. There is no correlation between the two-folding time-scale and luminosity, although the sampling rate is poor. For most of the quasars th…