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Ultraviolet spectra and chromospheres of R stars.
Johnson, H. R.; Eaton, J. A.; Obrien, G. T. +1 more
Long-wavelength IUE spectra of 13 normal R stars and two hydrogen-deficient R0 supergiants were obtained. Early R stars are noted to have line spectra and levels of flux in the ultraviolet characteristic of G5-K2 III stars, whereas late R stars were observed to have colors and line spectra similar to late K and M stars, but with greatly enhanced s…
X-Ray Variability of the Am-Herculis Star CW1103+254
Stella, L.; Beuermann, K.
The AM Her star CW1103+254 was observed with the low-energy and the medium-energy instruments of EXOSAT on 3 occasions for a total of 10.5 orbital cycles. Both, soft and hard X-rays from CW1103+254 were detected. We report preliminary results on the time variability of the X-ray emission on time scales from 1 minute to 1 month.
Discovery of an accretion shock cone in 22 Vulpeculae.
Parsons, S. B.; Ahmad, I. A.
A previous report that 22 Vul is a zeta Aurigae-type eclipsing binary is supported by the discovery of evidence for an accretion shock cone in 22 Vul similar to those found in zeta Aurigae and 32 Cygni. Such systems consist of a cool supergiant star primary and a hot dwarf secondary (G3 Ib-II and B9 in the case of 22 Vul) and undergo atmospheric e…
EXOSAT Observations of Flare Stars and Coronal Heating
Rodono, M.; Butler, C. J.
A program of observation of dMe stars is described that has been undertaken with EXOSAT as part of a collaboration of groups at Armagh, Catania, and JILA (University of Colorado) for multiband coverage of flare stars. The following conclusions were drawn: (1) The LE X-ray flux varies continuously over time scales of 20 seconds to hours with many s…
The Extremely X-Ray Bright Wolf-Rayet Star HD193793
Pollock, A. M. T.
The Einstein Observatory showed that Wolf-Rayet stars have a much larger range in the ratio of X-ray to bolometric luminosity than normal early-type stars. EXOSAT measurements of HD193T93 (WCT+abs) show it to be extremely X-ray bright. This result is probably not connected with the infra-red and radio outburst that the star underwent in 1977. Othe…
Multicomponent Analysis of Total Cos-B Gamma-Ray Data at Intermediate Latitudes
Strong, A. W.; Mayer-Hasselwander, H. A.; Bloemen, J. B. G. M. +1 more
The final COS-B database has been used to study the gamma-ray emission in the latitude range 10° < |b| < 20° in terms of a four component model. The emissivity spectrum of the local interstellar medium is derived and compared with that found in previous studies. The intensity of the inverse-Compton component is determined from the fitting pr…
IUE observations of the contact binary XY Leonis.
Vilhu, O.; Rucinski, S. M.
IUE observations (FES light curves, LWR Mg II emission data, and an SWP spectrum) obtained on June 11, 1982 are reported for XY Leo. The Mg II fluxes were measured at two primary minima, one secondary minimum, and one orbital quadrature. The data are presented in tables and spectra and analyzed. The orbital-average relative flux f(Mg II)/f(bol) is…
EXOSAT observations of a 2,000-s intensity dip in Seyfert galaxy NGC4151
Cruise, A. M.; Whitehouse, D. R.
Variations in the flux from active galactic nuclei (AGN) allow the testing of models of their emission mechanisms. Various suggestions for the energy generation in AGNs require the existence of a compact object, with X rays generated deep in that object's potential well and, therefore, X-ray luminosity related directly to the object responsible fo…
Photometric and UV spectroscopic observations of 22 VUL at eclipse : observational evidence for an extended chromosphere of a solar type G supergiant.
Che-Bohnenstengel, A.; Schroeder, K. -P.
The solar spectral type supergiant (G3 Ib-II) of the 22 Vul binary has been observed photometrically and spectroscopically during its recent eclipse of the B9 V companion. From the new photometric observations the eclipse data given by Parsons and Ake (1984) can be slightly improved (period = 249.21 ± 0.2 days, mideclipse: JD 2446191.6 ± 0.2). The…
IRAS observations of MKN 501 with quasi-simultaneous observations at radio, near-infrared and ultraviolet wavelengths.
Di Cocco, G.; Coe, M. J.; Spinoglio, L. +9 more
The authors present quasi-simultaneous observations at radio, far-infrared, near-infrared and ultraviolet wavelengths of the BL Lac object MKN 501. Specifically, they have observed the source with the IRAS satellite, and they show that the best power-law fit to the 12 to 100 µm data gives a slope of index α = 0.55±0.1. They show that the com…