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The distances of highly evolved planetary nebulae
The central stars of highly evolved planetary nebulae (PNe) are expectedto have closely similar absolute visual magnitudes MV. Thisenables us to determine approximate distances to these sources where oneknows their central star visual magnitudes, and levels of extinction. Wefind that such an analysis implies values of D which are similar tothose determined by Phillips; Cahn, Kaler & Stanghellin; Acker, andDaub. However, our distances are very much smaller than those of Zhang;Bensby & Lundstrom, and van de Steene & Zijlstra. The reasonsfor these differences are discussed, and can be traced to errors in theassumed relation between brightness temperature and radius.Finally, we determine that the binary companions of such stars can be nobrighter than MV~ 6mag, implying a spectral type of K0 orlater in the case of main-sequence stars.

A reexamination of electron density diagnostics for ionized gaseous nebulae
We present a comparison of electron densities derived from opticalforbidden line diagnostic ratios for a sample of over a hundred nebulae.We consider four density indicators, the [O II]λ3729/λ3726, [S II] λ6716/λ6731, [Cl III]λ5517/λ5537 and [Ar IV] λ4711/λ4740 doubletratios. Except for a few H II regions for which data from the literaturewere used, diagnostic line ratios were derived from our own high qualityspectra. For the [O II] λ3729/λ3726 doublet ratio, we findthat our default atomic data set, consisting of transition probabilitiesfrom Zeippen (\cite{zeippen1982}) and collision strengths from Pradhan(\cite{pradhan}), fit the observations well, although at high electrondensities, the [O II] doublet ratio yields densities systematicallylower than those given by the [S II] λ6716/λ6731 doubletratio, suggesting that the ratio of transition probabilities of the [OII] doublet, A(λ3729)/A(λ3726), given by Zeippen(\cite{zeippen1982}) may need to be revised upwards by approximately 6per cent. Our analysis also shows that the more recent calculations of[O II] transition probabilities by Zeippen (\cite{zeippen1987a}) andcollision strengths by McLaughlin & Bell (\cite{mclaughlin}) areinconsistent with the observations at the high and low density limits,respectively, and can therefore be ruled out. We confirm the earlierresult of Copetti & Writzl (\cite{copetti2002}) that the [O II]transition probabilities calculated by Wiese et al. (\cite{wiese}) yieldelectron densities systematically lower than those deduced from the [SII] λ6716/λ6731 doublet ratio and that the discrepancy ismost likely caused by errors in the transition probabilities calculatedby Wiese et al. (\cite{wiese}). Using our default atomic data set for [OII], we find that Ne([O II])  Ne([S II]) ≈Ne([Cl III])< Ne([Ar IV]).

Angular dimensions of planetary nebulae
We have measured angular dimensions of 312 planetary nebulae from theirimages obtained in Hα (or Hα + [NII]). We have appliedthree methods of measurements: direct measurements at the 10% level ofthe peak surface brightness, Gaussian deconvolution and second-momentdeconvolution. The results from the three methods are compared andanalysed. We propose a simple deconvolution of the 10% levelmeasurements which significantly improves the reliability of thesemeasurements for compact and partially resolved nebulae. Gaussiandeconvolution gives consistent but somewhat underestimated diameterscompared to the 10% measurements. Second-moment deconvolution givesresults in poor agreement with those from the other two methods,especially for poorly resolved nebulae. From the results of measurementsand using the conclusions of our analysis we derive the final nebulardiameters which should be free from systematic differences between small(partially resolved) and extended (well resolved) objects in our sample.Table 1 is only available in electronic form athttp://www.edpsciences.org

A HUBBLE SPACE TELESCOPE Survey for Resolved Companions of Planetary Nebula Nuclei
We report the results of a Hubble Space Telescope ``snapshot'' surveyaimed at finding resolved binary companions of the central stars ofGalactic planetary nebulae (PNe). Using the the Wide Field and PlanetaryCamera and Wide Field Planetary Camera 2, we searched the fields of 113PNe for stars whose close proximity to the central star suggests aphysical association. In all, we find 10 binary nuclei that are verylikely to be physically associated and another six that are possiblebinary associations. By correcting for interstellar extinction andplacing the central stars' companions on the main sequence (or, in onecase, on the white dwarf cooling curve), we derive distances to theobjects, and thereby significantly increase the number of PNe withreliable distances. Comparison of our derived distances with thoseobtained from various statistical methods shows that all of the latterhave systematically overestimated the distances, by factors ranging upto a factor of 2 or more. We show that this error is most likely due tothe fact that the properties of our PNe with binary nuclei aresystematically different from those of PNe used heretofore to calibratestatistical methods. Specifically, our PNe tend to have lower surfacebrightnesses at the same physical radius than the traditionalcalibration objects. This difference may arise from a selection effect:the PNe in our survey are typically nearby, old nebulae, whereas most ofthe objects that calibrate statistical techniques are low-latitude, highsurface brightness, and more distant nebulae. As a result, thestatistical methods that seem to work well with samples of distant PNe,for example, those in the Galactic bulge or external galaxies, may notbe applicable to the more diverse population of local PNe. Our distancedeterminations could be improved with better knowledge of themetallicities of the individual nebulae and central stars, measurementsof proper motions and radial velocities for additional candidatecompanions, and deeper HST images of several of our new binary nuclei.

An atlas of images of Planetary Nebulae
A catalogue of narrowband CCD images of 100 southern and 1 northernPlanetary Nebulae is presented. The data are images taken in the lightof the Hα , Hβ , [OIII]500.7 nm, and [NII]658.4 nm lines. Foreach image we give the exposure time, the maximum extent of the nebula,and the seeing measured from the frames themselves. For ease ofreference, we have added an alphabetical list of the objects. Our listwill be useful for morphological studies of Planetary Nebulae, and iscomplementary to previously published lists, especially the one of\cite[Schwarz et al. (1992)]{sch92}. Based on observations obtained atthe European Southern Observatory, La Silla, Chile.

Detection of new emission structures around planetary nebulae
Deep monochromatic observations are presented for 22 galactic planetarynebulae (PNe) performed through narrow-band interference filters, in thedirect imaging mode with i) the New Zealand (MJUO) f/7.8 Mc-Lellantelescope, ii) the Observatoire de Haute Provence (OHP) f/6 120-cmtelescope, and iii) and the Siding Spring Observatory (SSO) ATT 2.3metre telescope. Some of them are observed for the first time.Conspicuous secondary structures are detected far around theconventional nebular pictures. Such features could be relics of earlymass ejections during the post-AGB phase of the progenitors.Alternatively, they are more plausibly projections of externalloops/bubbles of the ``bar-bell'' shape upon the waist (for face-onPNe). We suggest that such structures (cf. Sh 1-89, Hua 1997) areintrinsic to all PNe. Their apparently diverse morphologies would``simply'' result from projections of a same PN intrinsic structure atdifferent view angles onto the plane of sky and with respect to themajor axis as well. In addition we report the detection of a new nebulain the field of NGC 3699 (50'' distant). Absolute fluxes are providedfor three emission lines. The observations were carried out at theSiding Spring Observatory operated by the Australian NationalUniversity, Australia. NGC 6853 was observed at the Haute ProvenceObservatory-CNRS 1.20-m telescope, France.

Electron densities in planetary nebulae, and the unusual characteristics of the [S BT II] emission zone} ] densities in planetary nebulae
We investigate the radial variation of electron densities in planetarynebulae, using values of ne deriving from the [S ii]<~mbda6717/<~mbda6730 line ratio. As a result, we are able to showthat there is a sharp discontinuity in densities of order 1.4 dex closeto nebular radii R=0.1 pc. It is proposed, as a consequence, that mostnebulae contain two primary [S ii] emission zones, with densitiesdiffering by a factor ~ 10(2) . The intensity of emission from thedenser component increases by an order of magnitude where nebulae passfrom radiation to density-bound expansion regimes, resulting in acorresponding discontinuous jump in [S ii]/Hβ line ratios. Theorigins of these changes are not entirely clear, although one mechanismis investigated whereby the superwind outflows shock interact withexterior AGB envelopes. Finally, the derived trends in ne(R)are used to determine distances for a further 262 nebulae. The resultingdistance scale appears to be comparable to that of Daub (1982) and Cahnet al. (1992).

The kinematics of 867 galactic planetary nebulae
We present a compilation of radial velocities of 867 galactic planetarynebulae. Almost 900 new measurements are included. Previously publishedkinematical data are compared with the new high-resolution data toassess their accuracies. One of the largest samples in the literatureshows evidence for a systematic velocity offset. We calculate weightedaverages between all available data. Of the final values in thecatalogue, 90% have accuracies better than 20 km s(-1) . We use thiscompilation to derive kinematical parameters of the galacticdifferential rotation obtained from least-square fitting and toestablish the Disk rotation curve; we find no significal trend for thepresence of an increasing external rotation curve. We examine also therotation of the bulge; the derived curve is consistent with a linearlyincreasing rotation velocity with l: we find V_b,r=(9.9+/-1.3)l -(6.7+/-8.5) km s(-1) . A possible steeper gradient in the innermostregion is indicated. Table 2 is available in electronic form only, viaanonymous ftp to cdsarc.u-strasbg.fr ( or viahttp://cdsweb.u-strasbg.fr/Abstract.html

Planetary Nebulae in the NRAO VLA Sky Survey
The 1.4 GHz NRAO VLA Sky Survey (NVSS) images and source catalog wereused to detect radio emission from the 885 planetary nebulae north ofJ2000 declination delta = -40 deg in the Strasbourg-ESO Catalogue ofGalactic Planetary Nebulae. We identified 680 radio sources brighterthan about S = 2.5 mJy beam-1 (equivalent to T ~ 0.8 K in the 45" FWHMNVSS beam) with planetary nebulae by coincidence with accurate opticalpositions measured from Digitized Sky Survey (DSS) images. Totalextinction coefficients c at lambda = 4861 Angstroms were calculated forthe 429 planetary nebulae with available H beta fluxes and low free-freeoptical depths at 1.4 GHz. The variation of c with Galactic latitude andlongitude is consistent with the extinction being primarily interstellarand not intrinsic.

Properties That Cannot Be Explained by the Progenitors of Planetary Nebulae
I classify a large number of planetary nebulae (458) according to theprocess that caused their progenitors to blow axisymmetrical winds. Theclassification is based primarily on the morphologies of the differentplanetary nebulae, assuming that binary companions, stellar orsubstellar, are necessary in order to have axisymmetrical mass loss onthe asymptotic giant branch. I propose four evolutionary classes,according to the binary-model hypothesis: (1) Progenitors of planetarynebula that did not interact with any companion. These amount to ~10% ofall planetary nebulae. (2) Progenitors that interact with stellarcompanions that avoided a common envelope, 11^{+2}_{-3}% of all nebulae.(3) Progenitors that interact with stellar companions via a commonenvelope phase, 23^{+11}_{-5}% of all nebulae. (4) Progenitors thatinteract with substellar (i.e., planets and brown dwarfs) companions viaa common envelope phase, 56^{+5}_{-8}% of all nebulae. In order todefine and build the different classes, I start with clarifying somerelevant terms and processes related to binary evolution. I then discusskinematical and morphological properties of planetary nebulae thatappear to require the interaction of the planetary nebula progenitorsand/or their winds with companions, stellar or substellar.

A statistical distance scale for Galactic planetary nebulae
A statistical distance scale is proposed. It is based on the correlationbetween the ionized mass and the radius and the correlation between theradio continuum surface brightness temperature and the nebular radius.The proposed statistical distance scale is an average of the twodistances obtained while using the correlation. These correlations,calibrated based on the 1`32 planetary nebulae with well-determinedindividual distances by Zhang, can reproduce not only the averagedistance of a sample of Galactic Bulge planetary nebulae exactly at thedistance to the Galactic center, but also the expected Gaussiandistribution of their distances around the Galactic center. This newdistance scale is applied to 647 Galactic planetary nebulae. It isestimated that this distance scale can be accurate on average to35%-50%. Our statistical distance scale is in good agreement with theone recently proposed by Van de Steene and Zijlstra. The correlationsfound in this study can be attributed to the fact that the core mass ofthe central stars has a very sharp distribution, strongly peaked atapprox. 0.6 solar mass. We stress that the scatter seen in thestatistical distance scale is likely to be real. The scatter is causedby the fact that the core mass distribution, although narrow andstrongly peaked, has a finite width.

Elemental abundances for a sample of southern galactic planetary nebulae.
Abstract image available at:http://adsabs.harvard.edu/abs/1994MNRAS.271..257K

A catalogue HeII 4686 line intensities in Galactic planetary nebulae.
We have compiled the intensities of the HeII 4686 lines measured inGalactic planetary nebulae. We present a few observational diagramsrelated to this parameter, and discuss them with the help of theoreticaldiagrams obtained from simple model planetary nebulae surroundingevolving central stars of various masses. We determine the hydrogen andhelium Zanstra temperature for all the objects with accurate enoughdata. We argue that, for Galactic planetary nebulae as a whole, the maincause for the Zanstra discrepancy is leakage of stellar ionizing photonsfrom the nebulae.

Distances for Galactic planetary nebulae. II - A southern hemisphere survey
New integrated forbidden O II 3726, 3729 A doublet ratio observationsare presented of 65 southern Galactic PN, and their distances arederived. Integrated forbidden S II 6716, 6731 A double observations arealso given, and it is concluded that both density diagnostics yield thesame densities for a large homogeneous data set. Regions of extendedemission surrounding 23 of the objects are detected. Upper limits on theelectron densities are derived for these regions, and it is concludedthat the emission originate from regions of diffuse Galactic backgroundemission.

A catalogue of absolute fluxes and distances of planetary nebulae
The paper presents a complete list of averaged recalibrated absoluteH-beta fluxes, global (where possible) relative He II lambda 4686fluxes, 5 GHz radio flux densities, and H-alpha/H-beta interstellarextinction constants for 778 Galactic planetary nebulae. The catalogprovides much of the fundamental data required to generate Zanstratemperatures. When data with the lowest errors are selected, the opticaland radio/optical extinctions show a peculiar correlation, with theradio values slightly high at low extinction and notably low at highextinction. The data are used, along with the best estimates of angulardiameters, to calculate Shklovsky distances according to the Daub schemeon the scale used earlier by Cahn and Kaler (1971). Use of this distancescale shows approximate equality of the death rates of optically thickand optically thin planetary nebulae. The method gives the correctdistances to the Magellanic Clouds.

Distances for galactic planetary nebulae using mean forbidden O II doublet ratio electron densities
Forbidden O II 3726, 3729-A double ratios and electron densities arepresented for 68 galactic PN. For 45 of the objects, the doublet ratiosrepresent integrations over the whole of the nebula. Calibrationsrecently derived from the Magellanic Cloud PN are used to derivedistances for the majority of the nebulae. The typical forbidden O IIdensity at the transition point between an optically thick and thinnebula is 4500/cu cm. An extensive comparison is made between thedistances derived and previously published distances and distancescales. It is shown that the present distances, based on MagellanicCloud calibrations, yield consistency with independent distanceestimates. They also exhibit much greater self-consistency betweencentral star masses derived from luminosity vs Teff comparisons on theone hand, and from absolute magnitude vs evolutionary age comparisons onthe other. For the PN in this sample, rms electron densities, fillingfactors, and absolute radii are also derived.

Strasbourg - ESO catalogue of galactic planetary nebulae. Part 1; Part 2
Not Available

Statistical properties of winds in central stars of planetary nebulae
Results are presented of an investigation of 834 low-resolutionshort-wavelength primary spectra taken with the IUE satellite of 159planetary nebulae for the presence of stellar winds in the centralstars. It is found that about 60 percent of central stars have a stellarwind. The wind's existence is examined against the optical spectral typeof the star. Previous information is incorporated into an updated listof the edge velocities in the central stars having fast winds. Theyrange from 600 to 3500 km/s. A positive correlation between the edgevelocity of the stellar wind and the expansion velocity of the opticalnebula is found. This correlation is consistent with the multipleinteracting wind theory in the adiabatic case.

The absolute H-beta fluxes for galactic planetary nebulae
The absolute H-beta flux measurements from spectrophotometricobservations of about 880 galactic planetary nebulae are presented. Thegalactic coordinates of PNe and the adopted diameters for the nebulae inarcsec are given. The final values of the H-beta flux, corrected for thenebular extension, are presented and compared to the results of othermeasurements.

Direct photography of a sample of southern planetary nebulae near the Galactic plane
Images of a group of 52 emission-line objects located near the Galacticplane have been obtained using a broad-band V filter and two narrow-bandfilters centered at forbidden-line O III 5007 and H-alpha. The diametersmeasured in these plates have been compared with those reported earlierby other authors, and the differences found are discussed.

On the scale height of planetary nebulae
Based on the distribution at high galactic latitudes, the local scaleheight of planetary nebulae is determined. A value of 250 + or - 50 pcis found, assuming an exponential disk, or 190 + or - 40 pc in case ofan isothermal disk. This agrees well with the old stellar disk. Theresult is considerably higher than earlier determinations; thedifference can be explained by the use of statistical distance scales inthe earlier work. The majority of the nearby planetary nebulae thereforeoriginates from old stars. The total number of pn in the galactic diskis found to be 23,000 + or - 6,000. The birthrate of planetary nebulaeis consistent with the white dwarf birthrate.

Winds in Central Stars of Planetary Nebulae
Not Available

Photospheric Abundances in Central Stars of Planeteray Nebulae, and Evolutionary Implications
Not Available

Large planetary nebulae and their significance to the late stages of stellar evolution
Spectrophotometry of 75 large PNe with Shklovsky radii greater than 0.15pc is presented and used to calculate nebular parameters andcompositions, stellar Zanstra temperatures and luminosities, and coremasses. Nine new Peimbert type I nebulae are identified. About 40percent of the stars that are on cooling tracks are above 0.7 solarmass, and over 15 percent are above 0.8 solar mass. The largeplanetaries demonstrate a clear positive correlation between nitrogenenrichment and core mass. N/O is anticorrelated with O/H. The radii ofthe nebulae whose stars lie along specific cooling tracks increasemonotonically with decreasing central star temperature. For a givencentral temperature, the nebular radii also increase with increasingcore mass, showing that in this part of the log L-log T plane the highermass cores evolve more slowly in agreement with theoretical prediction.However, theoretical evolutionary rates for the large nebulae starsappear to be much too slow.

A catalogue of expansion velocities of Galactic planetary nebulae
Published observational data on 288 Galactic PN are compiled in tables,graphs, and sketches based on spatiokinematical models and brieflycharacterized. The criteria used in selecting the data are discussed,and particular attention is given to the accuracies of the distanceestimates and their implications for theoretical models of PN or stellarevolution.

The absolute H-beta fluxes for southern planetary nebulae
The absolute H-beta fluxes of 462 southern PN are measured on 400-740-nmspectra obtained with a conventional spectrograph and theimage-dissector scanner on the 1.52-m telescope at ESO during 1984-1988.The data are presented in extensive tables and graphs and brieflycharacterized. The accuracy of the observations is considered adequatefor statistical analyses but not for detailed investigations ofindividual objects.

A study of some southern planetary nebulae
Radial velocities and expansions velocities (forbidden line O III,forbidden line O II, and He II) are measured for a sample of 64 southernGalactic planetary nebulae. Also, nebular electronic densities arederived from the forbidden line O II 3727, 3729 A double for 23 of theseobjects. The distance scale of Dopita et al. (1987) is used to derivedistances to 33 Galactic nebulae.

Multiple-shell planetary nebulae. I - Morphologies and frequency of occurrence
The physical nature of multiple shell planetary nebulae (MSPNs) arestudied using PN imagery survey data obtained at the Kitt Peak NationalObservatory during November 1982 and October 1985. The morphologies ofthe MSPNs are classified based on the relation between the shells andthe morphologies of the outer shell. It is observed that there are typeI MSPNs that have an outer shell with limb brightness, and type II whoseouter shell lacks brightness. The size of the outer shell, outer/innerradii ratio, radio luminosity of the whole nebula, and the outer/innersurface brightness ratio are analyzed in terms of morphology. It isobserved that for type I MSPNs, the outer shell is 0.5-1.0 pc, the radiiratio is greater than 2, and the surface brightness ratio is 0.005 orless; and for the type II nebulae, the shell size is 0.5 pc, the radiiratio is less than 2, and the inner surface brightness is 0.25. Thefrequency of multiple-shell occurrence is derived and compared withtheoretical predictions.

Photographic and spectroscopic observations of southern planetary nebulae.
Abstract image available at:http://adsabs.harvard.edu/abs/1987RMxAA..14..520M

Ultraviolet spectra of the central stars of large planetary nebulae
The ultraviolet spectra of 32 planetary nebula nuclei have been examinedwith the IUE. Ultraviolet and UV-to-optical flux ratios are derived,from which color temperatures are derived. The distribution of thelatter ranges from rough agreement with the Zanstra temperatures upwardto infinite values. The high-luminosity stars have generally lower,determinable color temperatures; the infinite or indeterminable colortemperatures are contained by the set of lower luminosity stars. Abouthalf the stars exhibit a mixture of line features, most commonly He II1640 A and C IV 1550 A in emission or absorption. Three display clear PCygni lines, while a fourth appears to display a remarkably broad C IV1550 A P Cygni profile. The other half of the stars have no perceptibleline features.

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Right ascension:21h59m35.20s
Apparent magnitude:99.9

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ICIC 5148

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