منابع مشابه
Emission-line Helium Abundances in Highly Obscured Nebulae
It has long been possible to determine He/H ratios from radio or infrared recombination lines, making it possible to measure ionic abundance ratios for highly obscured emission-line objects. It is not possible to determine the total helium abundance from such data alone, however, since the ionization correction factor (ICF), the correction for unobservable stages of ionization of He or H, must ...
متن کاملFluorine Abundances in Planetary Nebulae
We have determined fluorine abundances from the [F II] λ4789 and [F IV] λ4060 nebular emission lines for a sample of planetary nebulae (PNe). Our results show that fluorine is generally overabundant in PNe, thus providing new evidence for the synthesis of fluorine in asymptotic giant branch (AGB) stars. [F/O] is found to be positively correlated with the C/O abundance ratio, in agreement with t...
متن کاملEvolution of Gaseous Nebulae.
55Swain, F. M., A Blumentals, and N. Prokopovich, "Bituminous and other organic substances in Pre-Cambrian of Minnesota," Am. Assoc. Petrol. Geol. Bull., 42, 173-189 (1958). M Timofeev, B. V., "Spores and phytoplankton from Proterozoic and early Paleozoic of Eurasia," in Proc. 21st Int. Geol. Congr., Copenhagen, Rept. Soviet Geologists, Problem 9, 177-188 (1960) (in Russian; English abstract, p...
متن کاملAbundances in planetary nebulae: NGC 2792
The mid-infrared spectrum of the rather circular planetary nebula NGC 2792 taken with the Spitzer Space Telescope is presented. This spectrum is combined with the ultraviolet IUE spectrum and with the spectrum in the visual wavelength region to obtain a complete, extinction corrected, spectrum. The chemical composition of the nebula is then calculated in two ways. First by directly calculating ...
متن کاملDiscrepancy : Constraining the Iron Abundances in Nebulae
We study the current discrepancy between the model-predicted and measured concentrations of Fe and Fe in ionized nebulae. We calculate a set of photoionization models, updated with the atomic data relevant to the problem, and compare their results with those derived for the available nebulae where both [Fe III] and [Fe IV] lines have been measured. Our new model results are closer to the measur...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 1989
ISSN: 0074-1809
DOI: 10.1017/s0074180900138227