Search Publications
Ultraviolet spectral morphology of the O stars. IV. The OB supergiantsequence.
Walborn, Nolan R.; Nichols-Bohlin, Joy
An atlas of 25 O3 - B8 supergiant spectra in the wavelength ranges 1320 Å - 1580 Å and 1620 Å - 1880 Å is presented, based on high-resolution data from the International Ultraviolet Explorer archives. This remarkably detailed relationship between the stellar-wind profiles and the optical spectral classifications throughout this sequence is emphasi…
Photometry and spectroscopy of the O-type variable HD 167971.
Stahl, O.; Leitherer, C.; Zickgraf, F. -J. +9 more
The authors present photometric and spectroscopic observations of the O-type variable HD 167971. From a period analysis of the visual light-curve they find P = 3.3213 days. Combining the photometric and spectroscopic data they derive a consistent model for the system which can be understood in terms of a close O-type eclipsing binary and a third, …
The anomalous ultraviolet spectrum of the AM HER star H 0538+608.
Bonnet-Bidaud, J. M.; Mouchet, M.
The X-ray source H 0538 + 608, recently identified as an AM Her system, was observed with the IUE satellite and discovered to have a unique ultraviolet spectrum. The strong resonance emission lines commonly observed in the AM Her sources are present but with very unusual intensities: the C IV line is notably weak while N V strongly dominates, with…
Deterministic Chaos in Accreting Systems: Analysis of the X-Ray Variability of Herculis X-1
Voges, W.; Atmanspacher, H.; Scheingraber, H.
The irregular X-ray variability of Her X-1 has been investigated in different phases of the 1.7 day orbital period of the binary system Her X-1/HZ Her. The analyzed data have been sampled by the Exosat satellite during two main-on states of the 35 day cycle of the system. Using new system theoretical methods, the attractors of different processes …
Rotational modulation and flares on RS CVn and BY DRA stars. IV. The spatially resolved chromosphere of AR Lacertae.
Linsky, J. L.; Gary, D. E.; Walter, F. M. +4 more
The authors observed the RS CVn system AR Lacertae systematically over an orbital period with the International Ultraviolet Explorer in October 1983. Contemporaneous radio observations were obtained at the Very Large Array. The spectra of the Mg II k emission line were analyzed using a Doppler imaging technique. In this way, the authors identified…
Simultaneous observations of the X-ray and optical eclipse of SS 433 and their impplications.
Mazeh, T.; Matsuoka, M.; Watson, M. G. +9 more
The authors report on the results of coordinated X-ray and optical observations of SS433 made over one binary cycle. The optical light curve shows SS433 to be in a typical state, with two unequal minima separated by 0.5 in phase. The X-ray observations show reduced intensity coincident with the deeper, primary optical minimum. The authors interpre…
The Fading of the Narrow-Line Region in 3C 390.3
Clavel, J.; Wamsteker, W.
IUE spectra of 3C 390.3 obtained at 17 different epochs from 1978 to 1986 show that the flux in the narrow core of the Ly-alpha 1216 A and C IV 1550 A emission lines steadily declined by a factor of 1.7 and 3.2, respectively. Lloyd's optical monitoring reported in 1984 shows that the continuum intensity decreased by 2 mag over the years 1968-1980.…
A New Soft X-Ray Mode in the AM Herculis Object E2003+225
Mukai, Koji; Treves, Aldo; Maraschi, Laura +3 more
Exosat observations of the AM Her object E2003 + 225 made in June and September 1985, are presented together with optical and ultraviolet observations. The averages of soft X-ray count rate doubled between October 1983 and June 1985; the simultaneously measured V band intensity fell by a factor of 3 and the UV flux by 20 percent. The medium-energy…
The Local Interstellar Medium. VII. The Local Interstellar Wind and Interstellar Material in Front of the Nearby Star alpha Ophiuchi
Frisch, P. C.; York, D. G.; Fowler, J. R.
IUE observations of Mg I λ2852.127 are used to search for warm interstellar gas in the direction of α Oph. Mg I should be a sensitive tracer of warm gas because of dielectronic recombination. However, the authors show that the observed Mg I absorption feature is dominated by material associated with a wisp of relatively cool H I found at the posit…
Macroscopic Perturbations of the IMF by p/ Halley as Seen by the Giotto Magnetometer
Neubauer, F. M.; Raeder, J.; Burlaga, L. F. +1 more
Giotto magnetic field data have been used to analyze the macroscopic field structure in the vicinity of comet P/Halley. During the Giotto flyby at P/Halley the IMF showed quite a stable "away" polarity. Draping of magnetic field lines is clearly observed along the outbound leg of the trajectory. Inside the magnetic pile-up region the field reverse…