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NLTE analysis of sublimous O stars : the hot subdwarf in the binary system HD 128220.
Rauch, T.
We present a precise NLTE analysis of the hot subdwarf in the double-lined spectroscopic-binary system HD128220 (BD+19°2824, SAO 101094), based on 38 high- resolution IUE spectra. Very detailed NLTE models were constructed using the Accelerated Lambda Iteration technique. Model atoms for H I, He I/He II, C III/C IV, N III/N IV and O IV/O V are car…
Chromospheric Heating by Acoustic Shocks: A Confrontation of GHRS Observations of alpha Tauri (K5 III) with AB Initio Calculations
Judge, P. G.; Cuntz, M.
We compare ab initio calculations of semiforbidden C II line profiles near 2325 A with recently published observations of the inactive red giant Alpha Tau (K5 III) obtained using the GHRS on board the Hubble Space Telescope. Our one-dimensional, time-dependent calculations assume that the chromosphere is heated by stochastic acoustic shocks genera…
Ulysses plasma observations in the Jovian magnetosheath
Thomsen, M. F.; Smith, E. J.; Bame, S. J. +2 more
The solar wind plasma experiment aboard the Ulysses spacecraft, including separate ion and electron instruments, measured the plasma properties of the Jovian magnetosheath during the February 1992 encounter with Jupiter. Seven separate magnetosheath intervals were observed, as well as four bow shock crossings and numerous encounters with the magne…
Companions to Bright S and MS Stars: Technetium Deficiency and Binarity
Johnson, Hollis R.; Ake, Thomas B.; Ameen, Mudhaffer M.
To test the popular hypothesis that technetium-deficient stars of spectral types S and MS are mass-transfer binaries, we have searched for ultraviolet light from the putative hot secondaries in spectra taken with the SWP spectrograph of IUE. Although most S and MS stars are apparently thermally pulsing AGB (asymptotic giant branch) stars whose sur…
An Improved Ultraviolet Spectral Line List for the Symbiotic Star RR Telescopii
Feibelman, W. A.; Doschek, G. A.
We have remeasured wavelengths and intensities of International Ultraviolet Explorer (IUE) spectra of the symbiotic star, RR Tel. The main work is centered on the long 820 minute exposure high-resolution spectrum obtained on 1983 June 18. The list is intended to serve as a source of improved intensities and wavelengths for the ultraviolet spectrum…
Constraints for the shape of the UV background at z=2.
Reimers, D.; Vogel, S.
Spectroscopic UV observations with the Hubble Space Telescope of the QSO HS 1700+6416 (z = 2.72) (Reimers et al. 1992,1993) offer for the first time the possibility to measure column densities of C, N and O simultaneously in several ionization stages (O III to O VI, C III and C IV, N II to N V). Photoionization models have been computed and fitted…
High-Resolution Ultraviolet Observations of the Interstellar Diffuse Clouds toward MU Columbae
Savage, Blair D.; Sofia, Ulysses J.; Cardelli, Jason A.
Data obtained from the Goddard High Resolution spectrograph (GHRS) are used to study differences in gas-phase abundances of ions occurring in the diffuse neutral clouds toward mu Col. The sight-line characteristics determined in previous studies are reviewed and results for the cloud velocities, absorption equivalent widths, ion column densities, …
Variability of [O I] 6300-Å emission near Io
Smyth, W. H.; Scherb, F.
Observations of [O I] 6300-Å emission near Io have been obtained in 1990, 1991, and 1992 by the National Solar Observatory staff using the solar-stellar spectrograph on the McMath-Pierce telescope at Kitt Peak. High-resolution spectra with a resolving power of about 1.2×105 were obtained with an integration time of 10-15 min each. The v…
The discovery and properties of the ultra-soft X-ray transient EXO 1846-031.
Parmar, A. N.; White, N. E.; Angelini, L. +1 more
We report the discovery of a previously uncataloged ultra-soft X-ray transient EXO 1846-031 which was in outburst during 1985 April to September. The X-ray spectrum consists of an ultra-soft component and a high-energy power-law tail that extends to at least 25 keV. The ultra-soft component may be modeled by either a cutoff power-law or a multicol…
Metal-Line Blanketing and the Peculiar H beta Line Profile in the DAO Star Feige 55
Chayer, P.; Bergeron, P.; Wesemael, F. +1 more
A detailed analysis of the optical spectrum of the DAO white dwarf Feige 55 is presented. We show that the atmospheric parameters obtained from fits to the H-beta line and to higher Balmer lines, respectively, are discrepant. This problem is akin to that reported in previous analyses of hot DAO central stars of planetary nebulae. Model atmosphere …