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We present newly determined expansion velocities for a number of Planetary Nebulae (PNe) which have been observed with the ESO 1.4m CAT and the Coude' Echelle Spectrograph (CES), operated at a r.p. of 105, corresponding to a resolution of about 3km/s at Hα. Two detector systems have been used: the standard ESO Reticon and a two-dimensional photon-counting imaging detector developed at the A.I.T. (AIT-MCP-Camera).
During the ORFEUS-SPAS II mission (November 19th - December 7th 1996, aboard the space shuttle Columbia), the elliptical planetary nebulae NGC 6543 and NGC 6826 have been studied with the Echelle spectrometer. The instrumental wavelength range and resolution are 900Å - 1400Å and 0.1Å, respectively (R = 10000), which provides detailed information about emission and absorption lines which are inaccessible for ground-based observations. We present a new analysis of the absorption lines imposed on the spectra of the central stars.
During the ORFEUS-SPAS (Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer on the Shuttle Pallet Satellite) mission STS-51, flown in September 1993, we observed the central star of the planetary nebula NGC 6543 in the far ultraviolet (90 nm to 115 nm) wavelength region using the University of California, Berkeley spectrometer with a spectral resolution of 0.03 nm.
ORFEUS (Orbiting and Retrievable Far and Extreme Ultraviolet Spectrometer) is a 1 m normal incidence telescope for spectroscopic investigations of cosmic sources in the far and extreme ultraviolet spectral range. The instrument will be integrated into the freeflyer platform ASTRO-SPAS. ORFEUS-SPAS is scheduled with STS ENDEAVOUR in September 1992. We describe the telescope with its two spectrometers and their capabilities i.e. spectral range, resolution and overall sensitivity. The main classes of objects to be observed with the instrument are discussed and two examples of simulated spectra for the white dwarf HZ43 and an O9-star in the LMC are shown.
During the second flight of the ORFEUS-SPAS satellite (Nov./Dec. 96) high resolution (λ/∆λ = 10,000) Echelle-spectra of BD+28° 4211 in the wavelength regime 912–1400 Å have been taken. Deuterium can be clearly identified in the ORFEUSII Echelle-spectra of this star. For the first time it was possible to take spectra of faint, not redshifted objects in the far ultraviolet with a sufficient spectral resolution to study the deuterium column density in the whole spectral range of the Lyman-series down to the Lyman-limit. We obtained a value of log(ND) = 14.7 (±0.3) towards BD+28° 4211. The hydrogen column density has been determined using ORFEUS Echelle- and IUE-spectra of Ly-α (log(NH) = 19.8 (±0.2)). Thus a value of 8 × 10−6 can be obtained for the D/H-ratio on the line-of-sight towards BD+28° 4211.
Far UV high resolution spectra of 3 LMC and SMC stars were obtained with the Echelle spectrograph during the second ORFEUS mission in Dec. 1996. We present the first results from observations of the LMC star HDE 269546. We find definitely components of very hot gas identified as OVI and SVI absorption in the galactic halo of the Milky Way and in the LMC. Additionally, more than 30 ions of the most abundant elements in different stages of ionization can be identified in both our galaxy and the LMC. For the first time we can identify a significant absorption component of molecular hydrogen in the ORFEUS II Echelle spectrum with a redshift of 200 km s−1, doubtlessly to be attributed to the LMC.
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