Ultraviolet spectra of planetary nebulae – I. The abundance of carbon in IC 418

Harrington, J. P.; Lutz, J. H.; Seaton, M. J.; Stickland, D. J.

doi:10.1093/mnras/191.1.13

Cited by 44 publications

(26 citation statements)

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“…We used 20 pairs of hydrogen Balmer and Paschen lines arising from the same upper levels to find a reddening coefficient c Hβ = 0.34 ± 0.05. This value fits in the middle of the range of other published values including 0.25 from Harrington et al (1980), 0.29 from Mendez (1989), 0.21 from Hyung, Aller, & Feibelman (1994), 0.34 determined by Shaw & Dufour (1995) in their re-analysis of the Hyung, Aller, & Feibelman (1994) data, and 0.14 from Henry, Kwitter, & Bates (2000). This wide scatter may be due to differential reddening across the nebula and the differing regions imaged, and/or to the difficulty in determining an accurate reddening value due to differing qualities of flux calibration, and numbers and types of lines utilized in its calculation.…”

Section: Emission Line Identificationsupporting

confidence: 86%

Identification and Characterization of Faint Emission Lines in the Spectrum of the Planetary Nebula IC 418

Sharpee¹,

Baldwin²,

Williams³

2004

ApJ

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We present high signal-to-noise echelle spectra of the compact high surface brightness, low ionization planetary nebula IC 418. These reveal 807 emission lines down to intensities less than 10 −5 that of Hβ for which we determine widths and relative intensities. We show that line profiles are a valuable parameter for making line identifications and in constraining the excitation mechanism of the lines. We present evidence that indicates that many supposed high-level recombination lines may in fact be excited by a process other than recombination. We contend from the detection of dielectronic recombination lines that their relatively low intensities argue against their making a significant contribution to level populations of the heavy ions in this object. Following similar analyses of other PNe we find that IC 418 shows a small discrepancy in ion abundances derived from forbidden vs. recombination lines of the heavy elements.

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Section: Emission Line Identificationsupporting

confidence: 86%

Identification and Characterization of Faint Emission Lines in the Spectrum of the Planetary Nebula IC 418

Sharpee¹,

Baldwin²,

Williams³

2004

ApJ

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“…The C + /C 2+ ratio for IC 418 obtained from X2326 and A1908 was found to be larger than had been predicted from ionization models, by a factor of 5, and Harrington et al (1980) suggested that C 2+ ■* C + di-electronic recombination might be important. This was confirmed by Storey (1981 and review in the present volume) who shows that di-electronic recombination increases C /C 2 and C 2 /C 3 ratios and also leads to production of a number of spectrum lines, including C II A1335 and C III A2297.…”

Section: Carbon Abundancesmentioning

confidence: 69%

Some Recent Results from UV Observations

Seaton

1983

Symp. - Int. Astron. Union

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UV observations with IUE have led to recognition of the importance of di-electronic recombination in PN, for the calculation of ionization equilibria and for production of the features C II λ1335 and C III λ2297.The determination of C abundances is discussed. In high-excitation nebulae one must allow for absorption of C IV λ1549 by dust. It has been shown that C/O ≤ 0.5 for five PN with a silicate IR feature and that C/0 ≳ l for four with a SiC feature.Dust opacities τD have been deduced from observed ratios (C IV λ1549)/(C III λ2297) and (C II λ1335)/(C I λ4267). The values obtained, τD ≃ 0.1, are consistent with the observed strength of thermal infra-red emission.Earlier UV observations of PN were made by Pottasch et al. (1978) using ANS. Results obtained using IUE support neither their downward revisions of star temperatures nor their claim that a number of stars with TZ(He II) >> TZ (H I) are optically thick for H I.From IUE observations it is concluded that the planetary κ 648 in M 15 has C/O = 2.4 and that its central star has a temperature of 30 000 κ and a luminosity of 1700 L⊙.

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“…In addition the extinction determined by various authors from the Balmer decrement for the same (1) Hyung et al (1994), ICF; (2) Hyung et al (1994, model); (3) Henry et al (2000), (4) Harrington et al (1980, (5) Solar: Anders & Grevesse (1989; Allende Prieto et al (2001Prieto et al ( , 2002; Grevesse & Sauval (1998). (1) Hyung (1994), ICF; (2) Hyung (1994), model; (3) Kwitter et al (2003), (4) Solar: Anders & Grevesse (1989); Allende Prieto et al (2001Prieto et al ( , 2002; Grevesse & Sauval (1998).…”

Section: Errorsmentioning

confidence: 99%

Abundances of Planetary Nebulae IC 418, IC 2165 and NGC 5882

Pottasch

Bernard─Salas

Beintema

et al. 2004

A&A

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Abstract. The ISO and IUE spectra of the elliptical nebulae NGC 5882, IC 418 and IC 2165 are presented. These spectra are combined with the spectra in the visual wavelength region to obtain a complete, extinction corrected, spectrum. The chemical composition of the nebulae is then calculated and compared to previous determinations. A discussion is given of: (1) the recombination line abundances; (2) the exciting stars of the nebulae; and (3) possible evolutionary effects. IntroductionIC 418, IC 2165 and NGC 5882 are morphologically quite similar; they are usually classified as elliptical in shape, and they are located rather far from the galactic plane, which is probably an indication that they have been formed from low mass stars. They are all reasonably small nebulae on the sky, i.e. most of their emission comes from a small diameter. IC 2165 has a circular shape with a diameter of 8 . It is surrounded by two haloes (Corradi et al. 2003) but these have very little emission compared to the nebula itself. IC 418 is slightly larger, elliptical in shape, with a size of about 14 × 12 . It too is surrounded by a low level ionized halo, which in turn is surrounded by a region of neutral hydrogen which has a diameter of about 2 (Taylor et al. 1989). Finally NGC 5882 is more or less circular with a diameter of about 13-14 ; it contains several distinctive clumps of ionized material. It is also surrounded by low level emission which extends about three times as far (Guerrero & Manchado 1999), but it is less well studied than the other two nebulae.It is possible to define an axis of symmetry for all of these nebulae.The purpose of this paper is to study the element abundances in these nebulae with the help of the mid-infrared ISO spectra. Abundances in all three nebulae have been studied for many years already, but the inclusion of the ISO spectra permits a more accurate determination. The reasons for this have The most important advantage is that the infrared lines originate from very low energy levels and thus give an abundance which is not sensitive to the temperature in the nebula, nor to possible temperature fluctuations. Furthermore, when a line originating from a high-lying energy level in the same ion is observed, it is possible to determine an effective temperature at which the lines in that particular ion are formed. When the effective temperature for many ions can be determined, it is possible to make a plot of effective temperature against ionization potential, which can be used to determine the effective temperature for ions for which only lines originating from a high energy level are observed. Use of an effective electron temperature takes into account the fact that ions are formed in different regions of the nebula. At the same time possible temperature fluctuations are taken into account.Use of the ISO spectra have further advantages. One of them is that the number of observed ions used in the abundance analysis is approximately doubled, which removes the need for using large "Ionization Correction Fact...

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Ultraviolet spectra of planetary nebulae – I. The abundance of carbon in IC 418

Cited by 44 publications

References 0 publications

Identification and Characterization of Faint Emission Lines in the Spectrum of the Planetary Nebula IC 418

Identification and Characterization of Faint Emission Lines in the Spectrum of the Planetary Nebula IC 418

Some Recent Results from UV Observations

Abundances of Planetary Nebulae IC 418, IC 2165 and NGC 5882

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