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Fe - MG II K line fluorescence in K giant and bright giant stars.
Harper, G. M.
Emission lines of Fe I from the multiplet uv44 are observed at 2823.28A and 2843.98A in late-type giant and bright giant stars. It has been recognized for some time that these lines can be excited by Mg II k line radiation in the transition at 2795.54A. The first radiative transfer calculations to account for the strength of the Fe I lines Iota Au…
X-ray observations of the radio galaxy Pictor A.
Singh, K. P.; Rao, A. R.; Vahia, M. N.
strong X-ray emission is detected from the active nucleus of an emission- line radio galaxy Pictor A, during observations with the EXOSAT observatory. The nuclear X-ray emission is observed to be steady on time- scales of a few minutes to a few hours. The X-ray spectrum is adequately explained by a simple power law with the photon index {GAMMA} = …
An X-ray flare on the short-period, eclipsing binary UMa.
Jeffries, R. D.; Bedford, D. K.
An EXOSAT observation of a flare on the short-period, eclipsing RS CVn binary system XY UMa is reported. The light curve is interpreted within the framework of cooling plasma within loop-like magnetic structures, and limits on the flaring plasma and magnetic field parameters are derived using the light curve decay time and flare emission measure. …
The photospheric temperatures and composition of very hot He-rich white dwarfs.
Barstow, M. A.; Holberg, J. B.
Results are reported from a detailed analysis of Exosat observations of six hot He-rich white dwarfs belonging to, or related to, the spectroscopic subclass of PG1159 stars. These objects are thought to evolve directly from O VI type planetary nebulae nuclei and provide an important link in models of white dwarf evolution. When the Exosat data are…
The Changing Soft X-Ray Lightcurve of the Am-Herculis System Mr-Serpentis = PG:1550+191
Stella, L.; Osborne, J. P.; Angelini, L.
We report the first soft X-ray light curves of the AM Her system MR Ser, all obtained within a 4-month interval in 1984. The source was serendipitously detected on three occasions by the EXOSA T low-energy telescope, and one observation was made in which MR Ser was the target. MR Ser was probably in a high optical state throughout, although it was…
The long-period binary UU CANCRI as a system that has reversed its mass ratio.
Eaton, J. A.
UU Cnc is a 96-d binary system (K4 111+?) which has been interpreted as a contact binary, presumably representing the common-envelope stage of evolution. Since this is such a bizarre possibility, we have tested it by using the rotational velocity to determine the mass ratio and by obtaining lUE observations to search for the hot, accreting source …
The photospheric temperature and metal abundance of the compact star H 1504+65.
Barstow, M. A.; Tweedy, R. W.
A new analysis of an Exosat low-energy telescope observation of the hot compact star H1504 + 65 is presented. Earlier results had failed to take into account the large point-spread function produced by the boron filter, and hence the count rate had been underestimated by a large factor. On comparing the data with a new grid of model atmospheres co…
Gamma rays from dark clouds.
Feitzinger, J. V.; Stuewe, J. A.
The distribution of dark clouds and the COS-B X-ray observations of the local interstellar medium at intermediate galactic latitudes are compared. The dark cloud catalog of Lynds (1962) is combined with the complementary work of Feitzinger & Stuewe (1986) to obtain a uniform coverage of the medium-latitude sky. A good correlation between the e…
The EXOSAT spectral survey of AGN.
Turner, T. J.; Pounds, K. A.
Results are presented from EXOSAT Observations of 48 hard X-ray selected Seyfert type active galactic nuclei (AGN). These include all 30 of the emission line AGN in the Piccinotti sample. Combining EXOSAT LE and ME data has allowed us to obtain X-ray spectra over the broad energy range 0.1 - 10 keV spectra in the ~2-10 keV range are found to be we…
Spin modulated X-ray emission from intermediate polars.
Watson, M. G.; Norton, A. J.
This paper describes a comparative study of all the intermediate polars observed by Exosat. The X-ray pulse profiles of each source are presented, and it is shown that, in all cases, the modulation can be described in terms of an increasing depth with decreasing energy. By considering the pulse phase-resolved spectra, it is shown that the modulati…