The planetary nebula NGC 3918

Clegg, R. E. S.; Harrington, J. P.; Barlow, M. J.; Walsh, J. R.

doi:10.1086/165085

Cited by 72 publications

(73 citation statements)

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“…The physical conditions reported in Table 7 agree within the uncertainties with the physical conditions reported by Clegg et al (1987) and Tsamis et al (2003b).…”

Section: Physical Conditionssupporting

confidence: 80%

“…We also detect several forbidden and semi-forbidden lines from ions such as [N i] The depth of our spectra allows us to detect lines as fainter as 10 −5 ×I(Hβ). The identification and adopted laboratory wavelengths of the lines are based on several previous identifications in the literature (see Baluteau et al 1995;Clegg et al 1987;García-Rojas et al 2009Péquignot & Baluteau 1994;Sharpee et al 2007;Zhang et al 2005, and references therein). We also made use of Peter van Hoof's atomic line list v2.05B18 2 .…”

Section: Line Fluxes Identifications and Extinction Correctionmentioning

confidence: 99%

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s-process enrichment in the planetary nebula NGC 3918. Results from deep echelle spectrophotometry

García‐Rojas¹,

Madonna²,

Luridiana³

et al. 2015

Mon. Not. R. Astron. Soc.

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The chemical content of the planetary nebula NGC 3918 is investigated through deep, highresolution (R∼40000) UVES at VLT spectrophotometric data. We identify and measure more than 750 emission lines, making ours one of the deepest spectra ever taken for a planetary nebula. Among these lines we detect very faint lines of several neutron-capture elements (Se, Kr, Rb, and Xe), which enable us to compute their chemical abundances with unprecedented accuracy, thus constraining the efficiency of the s-process and convective dredge-up in NGC 3918s progenitor star. We find that Kr is strongly enriched in NGC 3918 and that Se is less enriched than Kr, in agreement with the results of previous papers and with predicted s-process nucleosynthesis. We also find that Xe is not as enriched by the s-process in NGC 3918 as is Kr and, therefore, that neutron exposure is typical of modestly subsolar metallicity AGB stars. A clear correlation is found when representing [Kr/O] vs. log(C/O) for NGC 3918 and other objects with detection of multiple ions of Kr in optical data, confirming that carbon is brought to the surface of AGB stars along with s-processed material during third dredge-up episodes, as predicted by nucleosynthesis models. We also detect numerous refractory element lines (Ca, K, Cr, Mn, Fe, Co, Ni, and Cu) and a large number of metal recombination lines of C, N, O, and Ne. We compute physical conditions from a large number of diagnostics, which are highly consistent among themselves assuming a three-zone ionization scheme. Thanks to the high ionization of NGC 3918 we detect a large number of recombination lines of multiple ionization stages of C, N, O and Ne. The abundances obtained for these elements by using recently-determined state-of-the-art ICF schemes or simply adding ionic abundances are in very good agreement, demonstrating the quality of the recent ICF scheme for high ionization planetary nebulae.

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“…The physical conditions reported in Table 7 agree within the uncertainties with the physical conditions reported by Clegg et al (1987) and Tsamis et al (2003b).…”

Section: Physical Conditionssupporting

confidence: 80%

Section: Line Fluxes Identifications and Extinction Correctionmentioning

confidence: 99%

s-process enrichment in the planetary nebula NGC 3918. Results from deep echelle spectrophotometry

García‐Rojas¹,

Madonna²,

Luridiana³

et al. 2015

Mon. Not. R. Astron. Soc.

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“…Clegg et al (1987) constructed a photoionisation model of this object using a biconical "pole-on" geometry. The model was used to derive the physical parameters of the central star and the nebular chemical abundances.…”

Section: The Modelling Of Ngc 3918mentioning

confidence: 99%

“…In model A, the density distribution assumed by Clegg et al (1987) was adopted. In model B a density distribution similar to that proposed by Corradi et al (1999) was used.…”

Section: The Modelling Of Ngc 3918mentioning

confidence: 99%

Three-Dimensional Monte Carlo Simulations of Ionised Nebulae

Ercolano¹,

Morisset²,

Barlow³

et al. 2003

Symp. - Int. Astron. Union

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Abstract. A three-dimensional self-consistent photo-ionisation code is developed using Monte Carlo techniques in order to build realistic models of photoionised nebulae of arbitrary geometry and density distribution. The code's results are benchmarked against those of estabilished codes. Two models are computed for the planetary nebula NGC 3918 using two different density distributions. The results of the two models are compared with the observations.

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“…Harrington: (3) These codes are discussed in Harrington (1968), Harrington et al (1982), and Clegg et al (1987). Most versions are for PNe; the radiation extends only to 200 eV.…”

Section: The Codesmentioning

confidence: 99%