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Recombination line abundances in NGC 6210
Published online by Cambridge University Press: 25 May 2016
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We present abundances derived from echelle spectroscopy of the planetary nebula NGC 6210 from the forbidden, collisionally excited lines, and from the permitted, recombination lines. We have obtained spectra from 3 positions in the nebula: at the central star, and 6 and 12 arcseconds south of the central star. We find a discrepancy of a factor of 2 between the O2+/H+ ratio derived by the recombination lines and by the forbidden lines in each spatial position. This discrepancy may result from the presence of temperature fluctuations in NGC 6210, where the collisionally excited lines are exponentially weighted to regions of higher temperature. A value for the root-mean-square temperature fluctuation parameter t2(OIIabun)= 0.038+0.007–0.009 is derived for the central star spectrum, 0.040+0.006–0.013 for the 6 arcsecond offset, and 0.051+0.014–0.015 for the 12 arcsecond offset spectrum. Thus no significant variation in t2 is seen as a function of spatial position within the nebula. We have also estimated t2 by comparing the derived Balmer Jump temperature at the 6 arcsecond offset, Te(BaJ)= 7900+2400–1600K, with the temperature derived from the [O III] 5007/4363å ratio Te[O III]= 9370±100K at this position. This comparison suggest t2(BaJ)= 0.041±0.020, in agreement with the values for t2 as estimated from the recombination lines.
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- IV. Envelopes
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- Copyright © Kluwer 1997