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EXOSAT Observations of 3C 371
Worrall, D. M.; Brunner, H.; Staubert, R.
The N galaxy/BL Lacertae object 3C 371 was observed by EXOSAT on two occasions separated by 18 days in September 1984. The low-energy and medium-energy X-ray flux has varied on the time scale of years (in comparison with HEAO 1 and Einstein Observatory measurements), 18 days (between the authors' two observations), and 8 hr to about 25 minutes wit…
Optical and UV spectroscopy of the peculiar RS CVn system RT Lacertae.
Huenemoerder, D. P.; Barden, S. C.
H-alpha and H-beta spectra of the peculiar double-lined RS CVn binary RT Lacertae have been obtained using the IUE, together with a ground-based coude-feed telescope at KPNO. The ground-based spectra show an asymmetry related to the orbital phase in the H-alpha profile. H-beta profiles showed excess emission in one hemisphere and excess absorption…
How Strong is the Evidence of Superionization and Large Mass Outflows in B/Be Stars? 2. The C IV and SI IV Lines in the UV Spectra of V 767 Cen, ο And, Θ CrB, λ Eri, and 59 CYG
Harmanec, P.; Hubeny, I.; Stefl, S.
The theoretical spectra in the neighborhood of the C IV and Si IV resonance lines have been compared with the published observed spectra of five Be stars, V 767 Cen, omicron And, Theta CrB, Lambda Eri, and 59 Cyg. It is shown that the published determinations of large outflow velocities evidenced by a violet asymmetry of the C IV and Si IV lines, …
Epsilon Aurigae: Polarization, Light Curves, and Geometry of the 1982--1984 Eclipse
Ake, T. B.; Simon, T.; Kemp, J. C. +5 more
Polarization and light curves of the recent eclipse of ɛ Aur are presented and modeled, using a tilted, opaque secondary disk and a model atmosphere for the F Ia primary star. That model qualitatively explains the striking asymmetries in the observed curves. But out-of-eclipse polarimetry shows the primary to be a nonradial pulsator, and this will…
Flares on dMe stars : IUE and optical observations of AT MIC and comparison of far-ultraviolet stellar and solar flares.
Bromage, G. E.; Dufton, P. L.; Phillips, K. J. H. +1 more
Observations of AT Mic obtained before and/or during a large flare on Sept. 19, 1980, using the short-wave and long-wave cameras of the IUE satellite, a UBV photometer on the 0.5-m SAAO telescope, and a 380-510-nm Cassegrain spectrophotometer on the 1.9-m SAAO telescope are reported. The data are presented in tables and graphs and compared with da…
Variability of Ultraviolet Emission in the Carbon Star TX PISCIUM
Johnson, Hollis R.; Baumert, John H.; Querci, Francois +1 more
Multiple low-resolution IUE observations of the cool carbon star TX Psc (NO; C6,2) permit an analysis of the variations in strength of the strongest emission lines - the Mg II line at 2800 Å, the C II line at 2330 Å, and certain Fe II lines. In the present sample of nine spectra, the integrated flux of the Mg II line varies by at least a factor of…
The Soft X-ray Spectra of Active Galactic Nuclei
Branduardi-Raymont, G.
EXOSAT LE and ME data on Seyfert 1 galaxies and quasars are reviewed: the observations indicate that a strong flux of soft X-rays, in excess of the power-law continuum that extends over most of the spectrum, is a common feature of the emission of active galactic nuclei (AGN). This low-energy X-ray spectral component, which is often identified with…
Differential emission measure distributions of Capella and σ2 CrB
Mewe, R.; Schrijver, C. J.; Lemen, J. R. +1 more
The active late-type stars Capella (α Aur G6III+F9III) and σ2 CrB (F6V+GV) (X-ray candidate emitters underlined) were observed with the EXOSAT Transmission Grating Spectrometer (TGS) in the region 10-200 Å. We have made an analysis of the differential emission measure (DEM) distribution. The derived DEM peaks between 3 and 7 MK and abov…
Ultraviolet Observations of Be Stars. II. Superionization in Be Stars of Different Spectral Types
Peters, Geraldine J.; Marlborough, J. M.
The results of an investigation of the dependence of the strength/presence of lines from superionized species (N V, C IV, Si IV) on spectral type and v sin i in the ultraviolet spectra of Be stars are presented. No evidence is found for N V in stars later than B2; this apparent absence may, however, simply reflect problems with the IUE reduction p…
Luminosity and colour variations of 88 HER through phase changes fromthe far UV to the visual region. I. A confrontation with traditional Be-star modelling.
Doazan, V.; Barylak, M.
In this paper, hereafter called Paper I, we present and analyze the luminosity and colour variations of 88 Her in the wavelength range 1550 Å-55OO Å, during the period 1972-1983 where the star has exhibited two different phases: a quasi-normal B phase and a new Be-shell phase of increasing strength. The observations show that: (i) The star is most…