A Molecular Disk around the Episodic Jets in K[CLC]j[/CLC]P[CLC]n[/CLC] 8

Huggins, P. J.; Bachiller, R.; Forveille, T.

doi:10.1086/310724

Cited by 73 publications

(161 citation statements)

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“…Nevertheless, for NGC 7027, the best studied object in the sample, in accordance with previous works, we have assumed the standard estimate of 0.7 kpc (see e.g. Huggins et al 1996). In the case of M 1-13, M 1-17 and IC 5117 the values of M m and M m /M i have been re-scaled from those given by Huggins et al (1996) according to our choice of distance (M m ∝ distance 2 and M m /M i ∝ distance −1/2 ) 1 .…”

Section: Pne Samplementioning

confidence: 92%

“…These are BV 5-1 (see Josselin & Bachiller 2001 for its CO content), K 3-94, K 3-24 (Josselin et al 2000), M 1-13, M1-17 and IC 5117 (Huggins et al 1996 and references therein). Although it was already observed by Bachiller et al (1997a), as representative of young PNe, we also observed NGC 7027 for comparison and calibration purposes.…”

Section: Pne Samplementioning

confidence: 99%

“…Although it was already observed by Bachiller et al (1997a), as representative of young PNe, we also observed NGC 7027 for comparison and calibration purposes. Table 1 lists the main properties of the observed nebulae: the most usual name (Col. 1), standard galactic name (2), kinematic distance -based on the simple approximation for the velocity structure of the Galactic disk of Burton (1974) -(3), optical size of the ionized nebula (4), radial and expansion velocities measured in the CO(2-1) line (5, 6), integrated intensity of the CO(2-1) line (7), mass of the molecular envelope (8), and ratio M m /M i between the molecular mass and the ionized mass (9), which is a good indicator of the evolutionary stage, almost independent of the distance (Huggins et al 1996). Concerning the distance, we have preferred the kinematic estimate over the statistical estimate, since we believe that the former is more precise in these cases (see Josselin et al 2000 for details).…”

Section: Pne Samplementioning

confidence: 99%

“…CO and H 2 surveys of PNe have revealed that a large fraction of the gas in massive PNe is in molecular form (Huggins et al 1996;Kastner et al 1996). This molecular component may be dominant during a large part of the evolution of the nebulae, and thus plays a prominent role in the mass distribution and the shaping of PNe.…”

Section: Introductionmentioning

confidence: 99%

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The chemistry of compact planetary nebulae

Josselin

Bachiller

2002

A&A

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Abstract. We report high-sensitivity millimetre observations of several molecular species ( 13 CO, HCN, HNC, CN, HCO + and N 2 H + ) in a sample of compact planetary nebulae. Some species such as HCO + and CN are particularly abundant compared to envelopes around AGB stars or even interstellar clouds. We have estimated the following average values for the column densities ratios: CN/HCN ∼ 2.6, HCO + /HCN ∼ 0.5, and HNC/HCN ∼ 0.4. Thus, the chemical composition of the molecular envelopes in these compact PNe appears somewhat intermediate between the composition of proto-PNe (such as CRL 2688 or CRL 618) and well evolved PNe (such as the Ring, M4-9, or the Helix). From observations of the CO isotopomers, we have estimated that the 12 C/ 13 C ratio is in the range 10 < ∼ 12 C/ 13 C < ∼ 40. These values are below those expected from standard asymptotic giant branch models and suggest non-standard mixing processes. The observed molecular abundances are compared to very recent modelling work, and we conclude that the observations are well explained, in general terms, by time-dependent gas-phase chemical models in which the ionization rate is enhanced by several orders of magnitude with respect to the average interstellar value. Thus, our observations confirm that the chemistry in the neutral shells of PNe is essentially governed by the high energy radiation from the hot central stars. The complexity of the chemical processes is increased by numerous factors linked to the properties of the central star and the geometry and degree of clumpiness of the envelope. Several aspects of the PN chemistry that remains to be understood are discussed within the frame of the available chemical models.

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Section: Pne Samplementioning

confidence: 92%

Section: Pne Samplementioning

confidence: 99%

Section: Pne Samplementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The chemistry of compact planetary nebulae

Josselin

Bachiller

2002

A&A

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“…If true, it would require either unknown processes that act to decrease the emission-line intensities below the collisional excitation rates or the existence of an appreciable amount of (presumably cool) gas that absorbs but does not radiate. The presence of significant amounts of neutral and low-ionization gas associated with ionized nebulae has been documented for various objects, and it may be a more extensive phenomenon than previously believed (Dinerstein et al 1995;Huggins et al 1996).…”

Section: Comparative Abundances and Emission Densitiesmentioning

confidence: 92%

Comparative Absorption and Emission Abundance Analyses of Nebulae: Ion Emission Densities for IC 418

Williams

Jenkins

Baldwin

et al. 2003

PUBL ASTRON SOC PAC

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ABSTRACT. Recent analyses of nebular spectra have resulted in discrepant abundances from CNO forbidden and recombination lines. We consider independent methods of determining ion abundances for emission nebulae, comparing ion emission measures with column densities derived from resonance absorption lines viewed against the central star continuum. Separate analyses of the nebular emission lines and the stellar UV absorption lines yield independent abundances for ions, and their ratio can be expressed in terms of a parameter , the An S e em "emission density" for each ion. Adequate data for this technique are still scarce, but separate analyses of spectra of the planetary nebula and central star of IC 418 do show discrepant abundances for several ions, especially Fe ii. The discrepancies are probably due to the presence of absorbing gas that does not emit and/or to uncertain atomic data and excitation processes, and they demonstrate the importance of applying the technique of combining emission-and absorption-line data in deriving abundances for nebulae.

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The Neutral Envelopes around AGB and Post-AGB Objects

Olofsson

2000

Symp. - Int. Astron. Union

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This review discusses the large-scale geometry and kinematics of envelopes around evolved stars, as inferred from radio line observations of circumstellar molecules, as a function of the evolutionary stage of the central object. In particular, the drastic change in morphology from largely spherical envelopes around asymptotic giant branch stars to distinctly non-spherical neutral envelopes around planetary nebulae is addressed. In addition, the small-scale structure of the envelopes, i.e., whether the circumstellar medium is smooth or clumpy, is discussed. Finally, a scenario for the morphological evolution, based on the assumption of a highly clumped medium, is presented.

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A Molecular Disk around the Episodic Jets in K[CLC]j[/CLC]P[CLC]n[/CLC] 8

Cited by 73 publications

References 4 publications

The chemistry of compact planetary nebulae

The chemistry of compact planetary nebulae

Comparative Absorption and Emission Abundance Analyses of Nebulae: Ion Emission Densities for IC 418

The Neutral Envelopes around AGB and Post-AGB Objects

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