Temperature and emission-measure distributions for several planetary nebulae

Basart, J. P.; Daub, C. T.

doi:10.1086/165286

Cited by 22 publications

(42 citation statements)

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“…Fluxes: (46) Aaquist & Kwok (1990), (47) Basart & Daub (1987), (48) Birkinshaw et al (1981), (49) Gathier et al (1983a), (50) Gathier et al (1983b), (51) Higgs (1971), (52) Isaacman (1984), (53) Milne & Aller (1975), (54) Milne & Aller (1982), (55) Phillips & Mampaso (1988), (56) Pottasch & Zijlstra (1994), (57) Purton et al (1982), (58) Ratag & Pottasch (1991), (59) Zijlstra et al (1989). Diameters: (60) Aaquist & Kwok (1990), (61) Bedding & Zijlstra (1994), (62) Cahn & Kaler (1971), (63) Chu et al (1987), (64) Dopita et al (1990), (65) Gathier et al (1983b), (66) Hua & Kwok (1999), (70) Mendez et al (1988), (71) Milne & Aller (1975), (72) Moreno et al (1988), (73) Perek & Kohoutek (1967), (74) Seaquist & Davies (1983), (75) Zijlstra et al (1989).…”

Section: Discussionmentioning

confidence: 99%

The distance scale of planetary nebulae

Bensby

Lundström

2001

A&A

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Abstract. By collecting distances from the literature, a set of 73 planetary nebulae with mean distances of high accuracy is derived. This sample is used for recalibration of the mass-radius relationship, used by many statistical distance methods. An attempt to correct for a statistical peculiarity, where errors in the distances influences the mass-radius relationship by increasing its slope, has been made for the first time. Distances to PNe in the Galactic Bulge, derived by this new method as well as other statistical methods from the last decade, are then used for the evaluation of these methods as distance indicators. In order of achieving a Bulge sample that is free from outliers we derive new criteria for Bulge membership. These criteria are much more stringent than those used hitherto, in the sense that they also discriminate against background objects. By splitting our Bulge sample in two, one with optically thick (small) PNe and one with optically thin (large) PNe, we find that our calibration is of higher accuracy than most other calibrations. Differences between the two subsamples, we believe, are due to the incompleteness of the Bulge sample, as well as the dominance of optical diameters in the "thin" sample and radio diameters in the "thick" sample. Our final conclusion is that statistical methods give distances that are at least as accurate as the ones obtained from many individual methods. Also, the "long" distance scale of Galactic PNe is confirmed.

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Section: Discussionmentioning

confidence: 99%

The distance scale of planetary nebulae

Bensby

Lundström

2001

A&A

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“…7 × 10 4 cm −3 (Basart & Daub 1987) and 14 000 K (Masson 1989). The total mass of the ionized region is 0.015 M .…”

Section: Ngc 7027mentioning

confidence: 98%

The evolution of planetary nebulae

Schönberner

Jacob

Steffen

2005

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Abstract.A detailed theoretical study of the basic internal kinematics of planetary nebulae is presented, based on 1D radiationhydrodynamics simulations of circumstellar envelopes around central stars of 0.595 and 0.696 M . By means of observable quantities like radial surface-brightness distributions and emission-line profiles computed from the models, a comparison with real objects was performed and revealed a reasonable agreement. This allowed to draw important conclusions by investigating the kinematics of these models in detail. Firstly, it is shown that the determination of kinematical ages, normally considered to be simple if size and expansion rate of an object are given, can seriously be flawed. Secondly, the expansion law of a planetary nebula is different from what is assumed for deriving spatio-kinematical models. Thirdly and most importantly, our hydrodynamical models help to correctly use existing angular expansion measurements for distance determinations. The mere combination of the angular expansion rates with the spectroscopic expansion velocities leads always to a serious underestimate of the distance, the degree of which depends on the evolutionary state of the object. The necessary correction factor varies between 3 and 1.3. Individual correction factors can be estimated with an accuracy of about 10% by matching our hydrodynamical models to real objects. As a result, revised distances for a few objects with reliable angular expansion rates are presented. But even these corrected distances are not always satisfying: they still appear to be inconsistent with other distance determinations and, even more disturbing, with the accepted theory of post-asymptotic giant branch evolution. As a byproduct of the angular expansion measurements, the transition times from the vicinity of the asymptotic giant branch to the planetary-nebula regime could be estimated. They appear to be shorter than assumed in the present evolutionary calculations.

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“…Adopted input parameters for the fitting of the radio spectra. Higgs 1971a,b; Aller & Milne 1972;Terzian & Dickey 1973;Cahn & Rubin 1974;Sistla et al 1974;Terzian et al 1974;Milne & Aller 1975;Harris & Scott 1976;Marsh et al 1976;Milne 1979;Milne & Webster 1979;Cohen & Barlow 1980;Ulich 1981;Calabretta 1982;Milne & Aller 1982;Purton et al 1982;Seaquist & Davis 1983;Gee et al 1984;Pottasch 1984;Turner & Terzian 1984;Gathier et al 1986;Basart & Daub 1987;Steppe et al 1988;Sahai et al 1989;Hoare et al 1992;Knapp et al 1993;Altenhoff et al 1994;Sandell 1994;Christianto & Seaquist 1998;Condon & Kaplan 1998;Bains et al 2003). The theoretical spectra shown in Fig.…”

Section: Comparing Calculated and Observed Radio Spectramentioning

confidence: 99%

Radio-continuum spectrum, brightness temperature, and planetary nebulae properties

Gruenwald¹,

Aleman²

2006

A&A

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Context. Radio-continuum spectra are frequently used to infer the density distribution of ionized gaseous regions, while observed correlations between the brightness temperature and other distance-independent parameters are used to test evolutionary models of planetary nebulae. Aims. We check empirical correlations among features derived from the observed radio data and the inferred conclusions available in the literature, using self-consistent photoionization models. Methods. Photoionization models are computed for the physical conditions of planetary nebulae in order to derive self-consistent radio-continuum spectra, as well as the brightness temperature. Results. The temperature and ionization distributions throughout the nebulae explain the observed range of spectral indexes in the thick region of the spectrum, even for a uniform density distribution, usually challenged in the literature. The obtained models fit the observed radio spectra for planetary nebulae in a large range of spectral indexes. Our calculations show a correlation between the spectral index obtained in a given frequency range and the nebula size, as well as reproduce the observed relations between the brightness temperature and other distance-independent parameters. Such diagrams are frequently used to check evolutionary models of the central star and/or of the nebula. Conclusions. Since PNe images clearly show that the density is not constant inside the nebulae, and models with uniform and nonuniform density distributions can both reproduce the observed radio spectra, we conclude that it is not possible to favour one of them from the radio data, or to infer a particular density distribution for planetary nebulae.

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Temperature and emission-measure distributions for several planetary nebulae

Cited by 22 publications

References 0 publications

The distance scale of planetary nebulae

The distance scale of planetary nebulae

The evolution of planetary nebulae

Radio-continuum spectrum, brightness temperature, and planetary nebulae properties

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