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GD 323: New Observations and Analysis of the Prototype DAB White Dwarf

Koester, D.; Saffer, Rex A.; Liebert, James

In this paper we present new spectroscopic observations of very high quality of the hybrid DAB white dwarf GD 323. GD 323 shows both hydrogen and helium lines and is located at an effective temperature (approximately equals 28,750 K), which places it at the hot end of the DB sequence just below the empirical DB gap. With recent results for the rel…

Rotational modulation and flares on RS Canum Venaticorum and BY Draconis stars. XVIII. Coordinated VLA, ROSAT, and IUE observations of RS CVn binaries .

Schmitt, J. H. M. M.; Bromage, G. E.; Pagano, I. +8 more

As part of a coordinated program of multi-wavelength observations of RS CVn close binary systems, we observed 15 systems with the VLA and 10 systems with IUE, simultaneously or nearly simultaneously with the ROSAT All Sky Survey observations of these stars. Of the 22 systems observed with ROSAT, three were observed both by IUE and the VLA. The pri…

The EUV spectrum of AU Microscopii: temperature and density diagnostic from EUVE Spectrometers observations.

Landini, M.; Monsignori Fossi, B. C.

EXOSAT and IUE observations of the active star AU Mic are used to develop a model of the differential emission measure distribution (DEM) versus temperature. The signals detectable by the Extreme UltraViolet Explorer Spectrometers are predicted. The computation indicates the presence of several highly ionized iron lines in the EUV spectral region.…

Optical, IUE, and ROSAT Observations of the Eclipsing Nova-like Variable V347 Puppis (LB 1800)

Raymond, John C.; Buckley, David A. H.; Mauche, Christopher W. +5 more

Using time-resolved optical spectroscopy and UBVRI and high-speed photometry obtained at Mount Stromlo Observatory, Mount John University Observatory, and the South African Astronomical Observatory; International Ultraviolet Explorer (IUE) ultraviolet spectroscopy; and Roentgen Satellite (ROSAT) survey X-ray fluxes, we present a study of the accre…

Interstellar and Intergalactic Magnesium and Sodium Absorption toward SN 1993J

Bowen, David V.; Meyer, David M.; Roth, Katherine C. +1 more

We present echelle-resolution (FWHM ~ 5 km s^-1^) HST observations of Mg II, Mg I, and ground-based observations of Na I absorption toward SN 1993J which exploded in M81. We detect individual absorption components spanning a total velocity range of -163 < ν_sun_ < +225 km s^-1^. The components are grouped into three subcomplexes, representin…

Spectroscopic binary orbits from ultraviolet radial velocities. Paper 14: HD 49798

Stickland, D. J.; Lloyd, C.

GHRS Spectroscopy of Individual Stars in R136a

Hubeny, Ivan; Heap, Sara R.; Malumuth, Eliot M. +3 more

The installation of the Corrective Optics Space Telescope Axial Replacement (COSTAR) Instrument on the Hubble Space Telescope (HST) makes it possible to observe stars in very crowded regions with high spatial and spectral purity. To demonstrate this capability, we have used the Goddard High Resolution Spectrograph (GHRS) to obtain spectra of two s…

ROSAT Observations of Cataclysmic Variables: A Search for the Boundary Layer Emission

Raymond, J. C.; Vrtilek, S. D.; Patterson, J. +1 more

Many cataclysmic variables (CVs) and low-mass X-ray binaries show He II line emission at wavelength 1640 and wavelength 4686. As recombination lines of an ion requiring 55 eV for ionization, these lines cannot be attributed to gravitational heating in the disk but could be due to reprocessed 55-280 eV X-rays which may be produced in a boundary lay…

The nature of the newly discovered DO white dwarf RE 0503-289.

Werner, K.; Barstow, M. A.; Holberg, J. B. +2 more

We report the discovery of a hot DO white dwarf, RE 0503 - 289, which lies in a region of very low interstellar H I density. It lies within 1 deg of the hot DA white dwarf RE 0457 - 281 which we have reported as having the lowest directly measured H I column. A follow-up observation made using the Voyager 2 UV spectrometer reveals a strong continu…

Concentration of interstellar pickup H⁺ and He⁺ in the solar wind

Geiss, J.; Giacalone, J.; Gloeckler, G. +1 more

We present observations of interstellar pickup hydrogen and helium in the solar wind which show large, highly-correlated fluctuations in flux which are not correlated significantly with the solar-wind hydrogen flux. The correlation of the fluctuations in the two species implies that the fluctuations are caused by transport after ionization. The la…