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Detection of Lyman alpha in the spectrum of a white dwarf with heliumatmosphere.
Koester, D.; Weidemann, V.
The detection of Ly-alpha absorption in a low dispersion IUE spectrum of the DBA white dwarf G200-39 is reported. The geocoronal emission was reduced by using a small aperture. For effective temperatures between 12,000 and 16,000, and log n(H)/n(He) values of -5, -4.5, -4, and -3.5, calculations giving colors and line strengths for He I 4472 A, H-…
The reflection nebula around HD 26676.
Centurion, M.; Vladilo, G.
The gaseous component of the reflection nebula surrounding HD 26676 is investigated by comparing the UV spectrum of the star with that of the foreground star HD 26793. The physical properties of the cloud are constrained under the assumption of Mg photoionization and H ionization by cosmic rays and taking into account the effect of the stellar rad…
Some Considerations of the Non-Detection of Interstellar li and B Towards the Supernova 1987A
Molaro, P.; Vladilo, G.
A very low upper limit of 0.15 mÅ for the interstellar λ6707 Å LiI line has been recently derived towards the SN1987a by Baade and Magain (1988). This value corresponds toN(Li)<1.4×1011 cm‑2 and gives [Li/H]<5.4×10‑11 assumingN(HI)=2.6×1021 cm‑2 for the hydrogen column density in the LMC…
Carbonaceous materials as components of cometary dust
Colangeli, L.; Fonti, S.; Bussoletti, E. +4 more
Recent exploration of comet Halley by space missions and ground-based observations have allowed to acquire a large amount of new information on cometary materials. In particular, IR spectroscopy has evidenced two pronounced and structured emission features at around 3.28 and 3.37 µm. Different kinds of gaseous molecules and/or solid grains i…
Chemical Abundances from B-Stars in the Magellanic Clouds
Stahl, O.; Wolf, B.; Reitermann, A. +1 more
We observed near-Main-Sequence B-stars in the Magellanic Clouds with the 3.6 m telescope and CASPEC at La Silla. We obtained spectra of high resolution and high S/N-ratio. The stars are members of the blue globular clusters NGC 1818 (LMC) and NGC 330 (SMC). The spectra are used for differential abundance analyses using ι HER as galactic reference …
Identification of surface features on comet P/Halley
Keller, H. U.; Reitsema, H. J.; Delamere, W. A.
The Giotto Halley Multicolour Camera obtained images of P/Halley that resolved the nucleus, showing active regions and other features on the surface. At least twenty-one discrete bright features can be identified in the images, and eight distinct regions associated with morphological characteristics can be recognized. The projected limb is approxi…
Mass Flow in Interacting Binaries Observed in the Ultraviolet
Kondo, Yoji
Recent satellite observations of close binary systems show that practically all binaries exhibit evidence of mass flow and that, where the observations are sufficiently detailed, a fraction of the matter flowing out of the mass-losing component is accreted by the companion and the remainder is lost from the binary system. The mass flow is not cons…
Chemically Peculiar Stars of the Upper Main Sequence.
Maitzen, H. M.
The Local Interstellar Medium - a Test-Bed for the Galactic Interstellar Medium
Molaro, P.; Beckman, J. E.; Vladilo, G. +1 more
We outline a method to explore the column density of the Local Interstellar Medium (LISM) using absorptions in the resonance H and K lines of MgII. The intrinsic strengths of these lines in the temperature and density conditions prevailing in warm clouds (Teff<104 K) in the LISM allows them to be used to explore many lines…
A New Narrow-Line Seyfert 1 Galaxy: IRAS 1652+395
Malkan, M. A.; Mandolesi, N.; Partridge, B. +3 more
Multiwavelength observations--from radio to X-rays--of IRAS 1652+395, a far-infrared and X-ray source serendipitously discovered in the field of the BL Lac object Mrk 501, are reported. They show that IRAS 1652+395 is a new Seyfert 1 galaxy at a redshift of z = 0.069. The Balmer emission lines are only slightly broader (~ 1000 km s^-1^ FWHM) than …