thesis - IRS, The Infrared Spectrograph

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64 CHAPTER 4: Abundances of Planetary Nebulae BD+30 3639 and NGC 6543to each upper limit in Ne ++ , S 3+ , Cl 3+ , is negligible. Ar 3+ and C 3+ have higher IP than forinstance S 3+ , therefore no contribution is expected. The upper limit to N ++ is at most 15%that of the total. The O ++ , which has similar IP, contributes less than 1%. Therefore we haveassumed that N ++ does not contribute to the abundance of nitrogen. Even considering a 15%of contribution will be within the errors that have been estimated to be 30%. Correctionsfor low unseen stages of ionization should also be estimated. Neutral nitrogen and oxygenhave been measured (very low abundance) and can help in deriving the neutral contributionof the other ions. The N 0 /N + and the O 0 /O + ratio is 0.023 and 0.01 respectively. The IPof nitrogen is 14.5 eV and that of oxygen 13.6 eV. Using this information and the IP of theions of interest the contribution can be inferred. These are the following: C 0 /H=6.0(-7);Ne 0 /H=1.26(-5); S 0 /H=< 1.3(−8); Ar 0 /H=2.0(-7); Cl 0 /H=< 5(−10). It can be seen that thecontribution is very small in all of them and negligible in carbon, sulfur and chlorine. Forneon and argon this contribution has been taken into account and is reflected in the ICF usedin Table 4.10. The helium abundance has not been derived because some of the helium isprobably neutral.A comparison of these abundances with those by Aller & Hyung (1995) is given in Table4.11. The nitrogen, sulfur and chlorine abundances agree very well. Aller & Hyung (1995)gave a lower limit for argon and neon because they could only measure one ionization stage(Ne II and Ar III). In this work we have been able to set an upper limit to the Ne III, whichturns out to be negligible. The Ar II has been measured and is the major contributor to thetotal abundance of argon. Using the infrared line at 6.9 µm, an abundance of [Ar II]=4.7(-6)is found; Aller & Hyung (1995) give an upper limit of 2.0(-7) for the argon abundanceusing optical data. The oxygen abundance is higher, although still within the errors, and canprobably be explained by the different extinction used.The abundances have been compared to those of the Sun and O, B stars in Table 4.11 andTable 4.12. The abundances of nitrogen and oxygen are very similar to solar. The carbonabundance is larger and the (C+N+O)Hratio is also larger than solar due to the enhancedcarbon. The N/O and C/O ratios are much higher than in the Sun and for O, B stars. Processessuch as the second dredge-up and hot bottom burning, in which carbon is destroyed, can nothave occurred. Since these processes need certain mass to occur this could set a limit on theprogenitor mass to be lower than 3 M ⊙ .4.7.2 NGC 6543The elemental abundances for 8 elements have been calculated and are given in Table 4.10.The ICF turns out to be 1 for seven cases. For carbon the ICF is 1.2 because some C 3+ mightbe present; but, considering its IP, and the fact that the O 3+ (with an IP of 54 eV) is not seen,it is expected that contribution of that stage of ionization should be small.These abundances are compared in Table 4.11 with those of Middlemass et al. (1989)and Hyung et al. (2000). The helium, neon and oxygen agree within the errors from thosefound by Middlemass et al. (1989). On the other hand they found more carbon and lessnitrogen. Compared with those by Hyung et al. (2000) carbon, oxygen, sulfur and argon aresimilar but the present nitrogen is again higher. The difference in the nitrogen abundanceis probably related to the large uncertainty in the ionic abundance of N ++ , which has been
Table 4.11–. Comparison of abundances in BD+30 3639 and NGC 6543.Element BD+30 3639 NGC 6543 Sun 1 O,B Stars 2Present abun. AH 3 Present abun. Mid 4 HA 5Helium 0.021 0.118 0.11 0.130 0.098Carbon(-4) 7.3 3.60 2.5 7.6 2.5 2.45 1.74Nitrogen(-4) 1.1 1.16 2.3 0.84 1.2 0.93 0.65Oxygen(-4) 4.6 3.78 5.5 6.4 4.7 4.90 4.17Neon(-4) 1.9 > 0.018 1.9 1.6 1.0 1.20 1.23Sulfur(-5) 0.64 0.71 1.3 0.8 1.86 1.23Chlorine(-7) 1.4 1.44 2.0 1.6 1.86 1.86Argon(-6) 5.2 > 0.2 4.2 3.0 3.631 Solar abundance from Grevesse & Noels (1993) and Anders & Grevesse (1989), except the oxygen andcarbon abundances that were taken from Allende Prieto et al. (2001) and Allende Prieto et al. (2002) respectively.2 O, B star abundances are the average of Gies & Lambert (1992) and Kilian-Montenbruck et al. (1994).3 From Aller & Hyung (1995).4 From Middlemass et al. (1989).5 From Hyung et al. (2000).4.7. Abundances 65
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RIJKSUNIVERSITEIT GRONINGENPhysics
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To my parents
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Contents1 Introduction 11.1 Evoluti
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CONTENTSvii5 Probing AGB nucleosynt
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1IntroductionPLANETARY NEBULAE are
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1.1. Evolution of low and intermedi
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1.2. Planetary Nebulae 5Flash−Dri
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1.3. Physics in PNe 7their whole li
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1.3. Physics in PNe 95.35 eVO IIIλ
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1.4. Studying PNe in the infrared 1
Page 21 and 22: 2The ISO-SWS Spectrum ofPlanetary N
Page 23 and 24: 2.3. Data reduction 15Table 2.1-. C
Page 25 and 26: 2.4. Line flux discussion 17Table 2
Page 27 and 28: 2.5. The visual and the ultraviolet
Page 29: 2.6. Analysis 21Table 2.5-. Electro
Page 32 and 33: 24 CHAPTER 2: The ISO-SWS Spectrum
Page 39 and 40: 3An ISO and IUE study of PlanetaryN
Page 41 and 42: 3.3. Corrections to line fluxes 33[
Page 43 and 44: 3.4. Line fluxes 35Table 3.1-. Comp
Page 45 and 46: Table 3.3-. IUE intensities, fluxes
Page 47 and 48: 3.5. Physical parameters 393.4.3 Op
Page 49 and 50: 3.5. Physical parameters 41Table 3.
Page 51 and 52: 3.6. Chemical abundances 43Table 3.
Page 53 and 54: 3.6. Chemical abundances 45Table 3.
Page 55: 3.7. Conclusions 47Acknowledgements
Page 58 and 59: 50 CHAPTER 4: Abundances of Planeta
Page 77 and 78: 5Probing AGB nucleosynthesis viaacc
Page 79 and 80: 5.1. Introduction 71about the synth
Page 81 and 82: Table 5.2-. Radius, Zanstra tempera
Page 83 and 84: 5.3. Accurate abundances of ISO-obs
Page 85 and 86: 5.3. Accurate abundances of ISO-obs
Page 87 and 88: 5.4. Nucleosynthesis in low- and in
Page 89 and 90: 5.5. Synthetic TP-AGB calculations
Page 91 and 92: 5.6. Comparison between models and
Page 111 and 112: 5.7. Summary and conclusions 103Fig
Page 113 and 114: 5.7. Summary and conclusions 105A s
Page 115 and 116: 6Physical Conditions in PDRs around
Page 117 and 118: 6.2. Observations 109are not promin
Page 119 and 120: 6.4. General parameters of the PNe
Page 121 and 122: 6.4. General parameters of the PNe
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Table 6.3-. Radius, Zanstra tempera
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6.6. Lines fluxes 117Figure 6.2-. S
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6.7. Physical conditions of the PDR
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6.8. PDRs versus Shocks 127Figure 6
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6.10. Atomic, ionized and molecular
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6.10. Atomic, ionized and molecular
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6.11. General discussion 133Table 6
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6.11. General discussion 135Figure
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6.12. Summary and Conclusions 137su
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7Conclusions and future workTHE res
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141• PNe with He/H > 0.14. The st
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143HERSCHEL The launch of this sate
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Nederlandse SamenvattingSTERREN wor
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Nederlandse Samenvatting 147Figuur
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Nederlandse Samenvatting 149PHOTOIO
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Nederlandse Samenvatting 151Figuur
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Nederlandse Samenvatting 153infraro
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English SummarySTARS are born, live
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English Summary 157Figure 2-. Two e
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English Summary 159PHOTOIONIZATIONR
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English Summary 161Figure 5-. Spect
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English Summary 163all) stages of i
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BibliographyAcker A., Marcout J., O
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BIBLIOGRAPHY 167Henry R.B.C., Kwitt
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BIBLIOGRAPHY 169Pottasch S.R., Bern
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List of PublicationsPublications in
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AcknowledgementsI could easily writ
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Acknowledgements 175sense of humor,
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