He Abundance in Planetary Nebulae
نویسندگان
چکیده
منابع مشابه
The iron abundance in four planetary nebulae
We have observed the high excitation planetary nebulae NGC 7027, NGC 6543 and the low excitation planetaries Hu 2-1 and Cn 3-1 in the optical & near IR with the aim to contribute accurate measurements of their gaseous iron abundances. Use was made of multi-level atomic models of iron ions to interpret the observed forbidden lines of various iron ions. The resulting total abundances are: N(Fe)/N...
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In this work, a review is given of some recent results and problems involved in the determination of chemical abundances of galactic planetary nebulae, particularly regarding disk and bulge objects.
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Presentamos observaciones de ĺıneas de recombinación de O II en diez nebulosas planetarias brillantes, y mediciones de O II y [O III] con resolución espacial en NGC 6720. Esto es con el fin de estudiar la discrepancia entre las abundancias calculadas con ĺıneas de recombinación de O II y aquellas derivadas de ĺıneas de excitación colisional de [O III]. Observamos una gran variación en la discre...
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Radial abundance gradients of the element ratios O/H, Ne/H, S/H, and Ar/H are determined on the basis of a sample of disk planetary nebulae. The behaviour of the gradients at large distances from the galactic centre, R > R0 = 7.6 kpc, is emphasized. It is concluded that the derived gradients are consistent with an approximately constant slope in the inner parts of the Galaxy, and some flattenin...
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We have studied the time variation of the radial abundance gradients using samples of planetary nebulae, open clusters, cepheids and other young objects. Based on the analysis of O/H and S/H abundances for planetary nebulae and metallicities of the remaining objects, we concluded that the gradients have been flattening out in the last 8 Gyr with an average rate of the order of 0.005 – 0.010 dex...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 2000
ISSN: 0074-1809
DOI: 10.1017/s0074180900167099