Search Publications
Population Synthesis in Starburst Galaxies - MARKARIAN:710
Mas-Hesse, J. M.; Kunth, D.; Arnault, P.
Evolutionary population synthesis models have been built to study the properties of the starforming processes taking place in starburst regions. BothZ⊙ andZ⊙/10 stellar evolutionary tracks have been used to take into account that starburst galaxies are generally metal deficient. A very small time step allows us to follow the …
Experimental plasma parameters at comet Halley
Amata, E.; Formisano, V.; Wilken, B. +3 more
Bulk speed, density and temperature of the plasma are computed for protons and water-group ions in comet P/Halley using data from the two ion sensors of the JPA experiment flown on Giotto. Two water group ion populations, locally generated and implanted further upstream, evolve with different density and temperature during the fly-by. The centre o…
A Simple Population Synthesis Model for the Continuum of the SEYFERT-2 Galaxy MARKARIAN:348
Terlevich, Roberto; Terlevich, Elena; Diaz, Angeles I. +1 more
The spectral energy distribution of the Seyfert type-2 galaxy Mk 348 is analyzed based on IUE observations and published data. It is found that most of the optical and near-IR flux comes from the underlying galaxy bulge population. The rest of the emission can be fitted by a power law of the formFv ∼v‑α with α=0.6. In order t…
Systematic Errors in Spectral Features Introduced by Random Noise
Joseph, Charles L.
A common IUE computer routine for measuring equivalent widths is shown to introduce systematic errors in data containing large amounts of noise. During statistical tests using simulations of synthetic spectral features with noise characteristics similar to those of the IUE, the routine was found to overestimate the true strength of an absorption l…
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…