Discovery of Extended X-Ray Emission from the Planetary Nebula NGC 7027 by the [ITAL]Chandra X-Ray Observatory[/ITAL]

Kastner, Joel H.; Vrtilek, S. D.; Soker, Noam

doi:10.1086/319651

Cited by 91 publications

(122 citation statements)

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“…H þ 3 can be produced through ionization of H 2 by cosmic-ray or soft X-ray emission from the central star. Since strong X-ray emission from NGC 7027 has been detected (Kastner et al 2001), it is possible that X-ray emission may play an key role in the formation of N 2 H + in NGC 7027. This is consistent with the fact that more evolved PNs generally have weaker X-ray emission and have no N 2 H + emission.…”

Section: Hmentioning

confidence: 99%

A Spectral Line Survey of NGC 7027 at Millimeter Wavelengths

Zhang

Kwok

Dinh-V-Trung

2008

ApJ

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We report on a recent spectral line survey of the planetary nebula (PN ) NGC 7027 using the Arizona Radio Observatory (ARO) 12 m telescope and the Heinrich Hertz Submillimeter Telescope (SMT) at millimeter wavelengths. The spectra covering the frequency ranges 71Y111, 157Y161, and 218Y267 GHz were obtained with a typical sensitivity of rms < 8 mK. A total of 67 spectral lines are detected, 21 of which are identified with 8 molecular species, 32 with recombination lines from hydrogen and helium, and 14 remain unidentified. As the widths of emission lines from CO, other neutral molecules, molecular ions, and recombination of H + and He + are found to be different from each other, the line strengths and profiles are used to investigate the physical conditions and chemical processes of the neutral envelope of NGC 7027. The column densities and fractional abundances relative to the H 2 of the observed molecular species are calculated and compared with predictions from chemical models. We found evidence for overabundance of N 2 H + and underabundance of CS and HNC in NGC 7027, suggesting that X-ray emission and shock waves may play an important role in the chemistry of the hot molecular envelope of the young PN.

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Section: Hmentioning

confidence: 99%

A Spectral Line Survey of NGC 7027 at Millimeter Wavelengths

Zhang

Kwok

Dinh-V-Trung

2008

ApJ

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“…The fast stellar wind would carve out a hot bubble in the interior of the nebula that would emit primarily in X-rays. Clear evidence for such hot bubbles has been found recently for a small number of PNe from X-ray imaging (Kastner et al 2000;Kastner, Vrtilek, & Soker 2001;Chu et al 2001). Mellema (1997) finds strong temperature variations from hydrodynamical simulations of bipolar PNe.…”

Section: And Referencesmentioning

confidence: 84%

Temperature Variations and Abundance Determinations in Planetary Nebulae

Torres-Peimbert

Peimbert

2003

Symp. - Int. Astron. Union

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Abstract. It is argued that an important fraction of PNe present large temperature variations that are not due to observational errors nor to incomplete atomic physics. Seven possible causes for these variations are reviewed, one of them is presented for the first time. OverviewPhotoionization models for chemically homogeneous gaseous nebulae of constant density predict an almost constant temperature and consequently very often observers assume a constant temperature to determine chemical abundances. There is growing observational evidence that indicates the presence of large temperature variations in gaseous nebulae, in contradiction with the models mentioned above. Consequently the relevance of temperature variations in the abundance determinations has to be considered in detail.In section 2 we review the observational evidence in favor of large temperature variations. In section 3 we review different possible explanations for the observed variations. In section 4 we discuss the implications of the temperature variations in the abundance determinations, these implications depend on the source of the temperature variations. Recent reviews on the temperature structure of gaseous nebulae are those of Peimbert, M. (1995), Esteban (2002), Stasińska (2002, 2002b. Temperature Variations DefinitionsThe average temperature, T 0 , and the mean square temperature fluctuation, t 2 , are given byandrespectively, where N e and N i are the electron and the ion densities of the observed emission line and V is the observed volume (Peimbert 1967).

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“…The Chandra X-ray satellite observation shows the bipolar X-ray emission of T eff~1 000,000K in the main shell (Kastner et al, 2001). Apparently, NGC 7027 just experienced the first few hundred years of kinematically unstable phase, right after leaving its AGB phase.…”

Section: Line Profile and Shell Expansion Velocitymentioning

confidence: 99%