The chromatic behaviour of the IAC analyzer, commonly used at the German Vacuum Gregory-Coude telesope at the Spanish Observatorio del Teide (Canary Islands), is investigated. It is shown that, through careful alignment of the optical components, a nearly perfect circular analysis can be obtained at wavelengths of 4000 Å and 6000 Å. For other

The new observational O/Fe versus Fe/H abundance relationship for halo stars is studied in terms of several models of chemical evolution for the solar neighborhood. Nucleosynthesis products from type I (both Ia and Ib) and Type II SNs are taken into account. The behavior of the O/Fe ratio for halo and disk stars is well reproduced by assuming (1) a

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The GOLF experiment on the SOHO mission will study the internal structure of the sun by measuring the spectrum of global oscillations in the frequency range 10-7 to 6 10-3 Hz. Both p and g mode oscillations will be investigated, with the emphasis on the low order long period waves which penetrate the solar core. The instrument employs an extension

The extinction law in the well-defined dust lane of the Sombrero galaxy, NGC 4594, was studied. In the R, I, J, H, and K bands good agreement is found between values for the extinction ratios A(lambda)/A(v) in NGC 4594 and those reported for the Galaxy. The apparently somewhat lower values in the B and V-bands can be explained with a scenario where

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