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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…
EXOSAT Observations of the TYCHO Supernova Remnant
Robba, N. R.; Taylor, B. G.; Smith, A. +3 more
The Gas Scintillation Proportional Counter and the Medium Energy Instruments on board EXOSAT were used to measure the X-ray spectrum of the Tycho supernova remnant over the range 1.5 - 10 keV. The emission lines due to S, Ar, Ca, and Fe (≡6.48 keV) are clearly resolved from the underlying continuum which is measured to have a temperature of 6.5±0.…
Indirect IUE Observations of O VI from Photoexcited Fluorescence Lines of Fe ii, Present in the Spectrum of RR Telescopii
Johansson, Sveneric
A new, highly excited level of Fe II at 13.7 eV has been established by means of six lines in the laboratory spectrum below 2000 Å. Confirming transitions appear in the infrared region. Four of the ultraviolet lines coincide with previously unidentified lines in the IUE spectrum of RR Tel reported by Penston et al. (1983). One of the remaining UV …
Ultraviolet and Optical Spectrophotometry of the Seyfert 1.8 Galaxy Markarian 609
Cohen, Ross D.; Ake, T. B.; Rudy, Richard J.
We present simultaneous ultraviolet and optical observations of the Seyfert 1.8 galaxy Markarian 609. The broad hydrogen lines are in the ratio Lyα/Hβ/Hα = 16/1.0/5.0. The Hβ(broad)/[O III] ratio has increased since the 1976 measurements of Osterbrock, and the Hα/Hβ ratio is no longer as large as when he classified Mrk 609 as a type 1.8 Seyfert ga…
An Exceptionally Bright, Compact Starburst Nucleus
Anderson, Scott F.; Massey, Philip; Mateo, Mario +2 more
We report observations of a remarkably bright (V ~ 13) starburst nucleus, 0833+652, which we have detected at radio, infrared, optical, ultraviolet, and X-ray wavelengths. Despite an observed flux at each of these wavelengths which is comparable to that of NGC 7714, often considered the "prototypical" example of the starburst phenomenon, 0833+652 …
The Detection of a High-Energy Break in the X-Ray Spectrum of the BL Lacertae Object PKS 0548-32
Maccagni, D.; Giommi, P.; Barr, P.
The results of a deep EXOSAT observation of the BL Lac object PKS 0548-32 performed in 1986 March are presented. The 0.05-10 keV X-ray spectrum is characterized by a relatively flat (power-law energy spectral index α ~ 0.9) continuum below 5 keV which steepens at higher energies. There is no evidence for any excess absorption intrinsic to the BL L…
An X-Ray Flare from a B9+ Post--T Tauri Star System in the Field of the Seyfert Galaxy III ZW 2
Tagliaferri, G.; Pallavicini, R.; Giommi, P. +2 more
We report the serendipitous discovery by EXOSAT of a flaring X-ray source in the field of the Seyfert type I galaxy III Zw 2. In contrast to an earlier report that attributed the variability observed by the medium energy experiment to III Zw 2, we show that the variability was entirely due to the serendipitous source. We identify this source with …
Stellar Winds in the Small Magellanic Cloud
Fitzpatrick, Edward L.; Garmany, Catharine D.
According to the predictions of line-driven stellar wind theory, the mass loss from luminous stars should be proportional to some power of the metallicity, yet previous studies have not shown this effect clearly. We have observed 22 main-sequence and giant O-type stars in the SMC with the low-resolution mode of the IUE in order to study the stella…
Fast Variations in the Ultraviolet Resonance Lines of alpha Camelopardalis (O9.5 Ia): Evidence for Blobs in the Wind
Snow, Theodore P.; Lamers, Henry J. G. L. M.; de Jager, Cornelis +1 more
The 72 IUE spectra of Alpha Cam and 19 IUE spectra of Kappa Cas, obtained during 72 hours of continuous IUE time in September 1978 were searched for variations in the profiles of the resonance lines of Si IV, C IV, and N V, and the results are discussed. The UV resonance lines in the spectra of Alpha Cam showed variations at the 2 percent level ne…