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Article: A chemical model of the neutral envelope of the planetary nebula NGC 7027

TitleA chemical model of the neutral envelope of the planetary nebula NGC 7027
Authors
KeywordsIsm: Molecules
Molecular Processes
Planetary Nebulae: Individual (Ngc 7027)
Issue Date2000
PublisherInstitute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/0004-637X
Citation
The Astrophysical Journal, 2000, v. 532 n. 2 pt. 1, p. 994-1005 How to Cite?
AbstractIn response to the recent molecular observations by ISO and millimeter-wave telescopes, we have developed a spherically symmetric, steady state chemical model for the planetary nebula NGC 7027. In our model, the neutral envelope consists of a geometrically thin, high-density shell of constant density and an outer stellar wind region with an inverse-square law density profile. The neutral envelope is subjected to ultraviolet (UV) radiation both from the central star and from the external interstellar field. Under an assumed visual extinction of 4 mag for the neutral envelope, the gas in our model is half molecular and half atomic. Simple molecules such as CH, CH +, OH are abundantly formed at an assumed gas temperature of 800 K in the partially molecular shell. The presence of molecular ions such as HCO + and CO + is well explained by photochemistry at high temperatures. The model CN/HCN ratio is almost constant at about 30 throughout the wind region and is 1-10 in the dense shell, comparable to observed values in planetary nebulae. Our model suggests that molecules are as efficiently formed with timescales shorter than 100 yr as they are photodissociated in the neutral envelope of NGC 7027 and probably in other young planetary nebulae.
Persistent Identifierhttp://hdl.handle.net/10722/179653
ISSN
2015 Impact Factor: 5.909
2015 SCImago Journal Rankings: 3.266
References

 

DC FieldValueLanguage
dc.contributor.authorHasegawa, Ten_US
dc.contributor.authorVolk, Ken_US
dc.contributor.authorKwok, Sen_US
dc.date.accessioned2012-12-19T10:02:16Z-
dc.date.available2012-12-19T10:02:16Z-
dc.date.issued2000en_US
dc.identifier.citationThe Astrophysical Journal, 2000, v. 532 n. 2 pt. 1, p. 994-1005en_US
dc.identifier.issn0004-637Xen_US
dc.identifier.urihttp://hdl.handle.net/10722/179653-
dc.description.abstractIn response to the recent molecular observations by ISO and millimeter-wave telescopes, we have developed a spherically symmetric, steady state chemical model for the planetary nebula NGC 7027. In our model, the neutral envelope consists of a geometrically thin, high-density shell of constant density and an outer stellar wind region with an inverse-square law density profile. The neutral envelope is subjected to ultraviolet (UV) radiation both from the central star and from the external interstellar field. Under an assumed visual extinction of 4 mag for the neutral envelope, the gas in our model is half molecular and half atomic. Simple molecules such as CH, CH +, OH are abundantly formed at an assumed gas temperature of 800 K in the partially molecular shell. The presence of molecular ions such as HCO + and CO + is well explained by photochemistry at high temperatures. The model CN/HCN ratio is almost constant at about 30 throughout the wind region and is 1-10 in the dense shell, comparable to observed values in planetary nebulae. Our model suggests that molecules are as efficiently formed with timescales shorter than 100 yr as they are photodissociated in the neutral envelope of NGC 7027 and probably in other young planetary nebulae.en_US
dc.languageengen_US
dc.publisherInstitute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/0004-637Xen_US
dc.relation.ispartofThe Astrophysical Journalen_US
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.subjectIsm: Moleculesen_US
dc.subjectMolecular Processesen_US
dc.subjectPlanetary Nebulae: Individual (Ngc 7027)en_US
dc.titleA chemical model of the neutral envelope of the planetary nebula NGC 7027en_US
dc.typeArticleen_US
dc.identifier.emailKwok, S: deannote@hku.hken_US
dc.identifier.authorityKwok, S=rp00716en_US
dc.description.naturepublished_or_final_versionen_US
dc.identifier.doi10.1086/308610-
dc.identifier.scopuseid_2-s2.0-0034164189en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0034164189&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume532en_US
dc.identifier.issue2 pt. 1en_US
dc.identifier.spage994en_US
dc.identifier.epage1005en_US
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridHasegawa, T=7404173711en_US
dc.identifier.scopusauthoridVolk, K=7006571965en_US
dc.identifier.scopusauthoridKwok, S=22980498300en_US

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