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[en] Star counts have been performed for rings centered on the carbon star at 1 69 degrees, b + 55 degrees at a distance of 60 kpc. The counts were performed in order to determine whether halo carbon stars might be situated in dwarf spheroidal galaxies which are too star-poor to have been recognized as galaxies. The counts were made on a IIIa-J plate baked in forming gas that was exposed for 40 minutes through a 2C filter with the Palomar 1.2-m Schmidt telescope. It is shown that the carbon star is not situated in a dwarf spheroidal galaxy brighter than M(V) 5.7
[en] We present a mid-infrared high spectral resolution spectrum of CRL618 in the frequency ranges 778-784 and 1227-1249 cm-1 (8.01-8.15 and 12.75-12.85 μm) taken with the Texas Echelon-cross-Echelle Spectrograph (TEXES) and the Infrared Telescope Facility (IRTF). We have identified more than 170 rovibrational lines arising from C2H2, HCN, C4H2, and C6H2. We have found no unmistakable trace of C8H2. The line profiles display a complex structure suggesting the presence of polyacetylenes in several components of the circumstellar envelope (CSE). We derive total column densities of 2.5 x 1017, 3.1 x 1017, 2.1 x 1017, 9.3 x 1016 cm-2, and ∼<5 x 1016 cm-2 for HCN, C2H2, C4H2, C6H2, and C8H2, respectively. The observations indicate that both the rotational and vibrational temperatures in the innermost CSE depend on the molecule, varying from 100 to 350 K for the rotational temperatures and 100 to 500 K for the vibrational temperatures. Our results support a chemistry in the innermost CSE based on radical-neutral reactions triggered by the intense UV radiation field.
[en] Several stars of this type have just been detected in galaxies where they were not suspected and where they reveal a recent activity not really corresponding to current ideas. Data given by these observations allow the astrophysicists to improve the galaxy evolution models, in particular the evolution model of our galaxy
[fr]Plusieurs etoiles de ce type viennent d'etre detectees dans des galaxies ou on ne les attendait guere et ou elles revelent une activite recente peu conforme aux idees couramment admises. Les renseignements cruciaux fournis par ces observations permettent aux astrophysiciens d'affiner les modeles d'evolution des galaxies, et de la notre en particulier
[en] A comparison between the General Catalogue of Cool Carbon Stars (CCS) and the AFGL Catalogue has been performed. Eighty-five stars have beeen found in common between the two lists. Eighty-four stars which were present in Baumert's comparison between CCS and the 2 μ Sky Survey have no counterpart in the AFGL. Four new tentative identifications are given. The analysis of the two colours diagrams K-[4.2 μ] vs. I-K and I-[4.2 μ] vs. [4.2 μ]-[11 μ] led to the conclusion that all the infrared emission from the sources seems to come from a single circumstellar shell. (orig.)
[en] The results of observations of 8 carbon stars for 1-2.5 μm wavelengths are presented. It is shown that some of the stars have infrared excess emission which is probably due to the circumstellar dustlike shells. The excess infrared emission depends on the carbon content of the corresponding stars. The found correlation contradicts the suggestion on the condensation of graphite particles in the atmospheres of carbon stars
[en] We present positions, identification charts, spectra in the wavelength range 4500-7000 A or 4000-7100 A and equivalent widths of the main lines and bands for the 34 carbon stars we have identified in 8 fields of the galactic bulge. Spectrophotometric data in the visible are provided as well as infrared J, H and K magnitudes for all these objects, and L magnitudes for about half of them. These data are used to derive intrinsic colors, effective temperatures and bolometric magnitudes given in a companion paper which discusses the properties and origin of these carbon stars
[en] An analysis of the fluorine abundance in Galactic asymptotic giant branch (AGB) carbon stars (24 N-type, 5 SC-type, and 5 J-type) is presented. This study uses the state-of-the-art carbon-rich atmosphere models and improved atomic and molecular line lists in the 2.3 μm region. Significantly lower F abundances are obtained in comparison to previous studies in the literature. This difference is mainly due to molecular blends. In the case of carbon stars of SC-type, differences in the model atmospheres are also relevant. The new F enhancements are now in agreement with the most recent theoretical nucleosynthesis models in low-mass AGB stars, solving the long-standing problem of F in Galactic AGB stars. Nevertheless, some SC-type carbon stars still show larger F abundances than predicted by stellar models. The possibility that these stars are of larger mass is briefly discussed.