We have performed nonradial pulsation analyses of the central star of the planetary nebula K1-16. K1-16 is a very unusual nebulae which appears to have ejected material that is very rich in helium. The central star shows no evidence for hydrogen in its spectrum and the helium and carbon lines are in emission. Grauer and Bond (Ap. J., 277, 211, 1984) discovered that it is pulsating with periods around 1700 sec. Although its spectral characteristics are similar to those of the PG1159-035 variables, it is pulsating in much longer periods than they are.

At present only a small number of planetary nebulae are known to possess binary nuclei. Since approximately 2/3 of main sequence stars are members of binary or multiple star systems, one might expect a large fraction of PN central stars to have gravitationally bound companions. Additionally, late-type stars are more numerous, and due to their low luminosities would be difficult to detect by visual observational methods at distances where PN are typically found (≧ 1 kpc). (Only 5 known PN are thought to be nearer than 0.5 kpc). It is thus possible, and in our view probable, that a significant number of PN nuclei possess cool companions, hitherto undetected.

We have examined the extraordinarily rich WC spectrum of the nucleus of He 2-99, an object closely akin to BD +30°3639. In all, we log 25 lines in the UV (λ1240-λ1950; λ2550-λ3150) and 89 in the optical between λ3610 and λ7065 (including a small number of nebular features). We provide a fundamental atlas for this class of star, wherein we give fluxes and identifications of the emission lines, including a detailed accounting of blends. The most powerful emissions are those of C III followed by C II and C IV. There is good indication that C I and even C V are present as well. Oxygen is well represented by O III; O II, O IV, and O V all appear present, but are generally confused by blends. Si III and Si IV appear, as do He I and He II. Other than N V, little case can be made for stellar nitrogen. The most serious barrier to analysis of the spectrum is the problem of coincidences and blends: there are few pure lines. Analysis of the nebular spectrum, which is severely contaminated by stellar line emission, indicates enrichment in carbon, but none in nitrogen.

The nucleus of the large, low surface brightness planetary nebula Abell 35 (Abell 1966) belongs to the small group of objects which are known to have a binary nucleus. From his photometric and spectroscopic study of the object, Jacoby (1981, Astrophys. J. 244,903) found the star SAO 181201, a G8 IV star, to be located near the apex of the parabolic region of enhanced [O III] emision which is completelely absent in H∝. The G8 IV star can clearly not be the ionising source for this nebulosity nor the larger scale nebulosity of the PN proper. Jacoby concluded that the central object must be a binary and suggested a hot subdwarf as the second component, which is masked in the optical by the bright SAO star. This interpretation is supported by the analysis of the DDO and UBVRI photometry, which shows that the observed colour indices can be fitted if one assumes a 50.000 K blackbody companion.

V605 Aquilae, whose novalike outburst was observed in 1919, is the central object of the old planetary nebula A58. It is the only ‘nova’ known with a hydrogen-deficient carbon-rich outburst spectrum and a remnant consisting of a WC-type star and a nebula which appears to be totally void of hydrogen. The star shows a red continuum of magnitude 22.3 and a prominent line of CIV 580.8 nm with a total width of 4400 km/sec Other lines are extremely weak. The remnant nebula shows only forbidden lines of heavy elements. The strongest ones are due to the nebular transitions of [OIII],[NII],[OI]. IR [OII] is present, other ions are suspected. The nebula is an IRAS point source of temperature 170 K.

We have undertaken at Palomar Observatory to obtain high resolution spectra of a large sample of planetary nebula nuclei (PNN) in order to systematically investigate their spectral morphologies and then to derive temperatures and surface gravities by comparing absorption line profiles to model atmospheres. We have taken as our sample all those central stars of planetary nebulae within 1.3 kpc of the sun according to the distance determinations of Daub (Ap, J., 260, 612, 1982); of the 94 objects in this unbiased sample, 64 are in the sky visible from Palomar and 33 have central stars bright enough to be observed at a resolution of 5 000 with an “echellette” spectrograph on the 5-m Hale telescope, leaving 7 PNN (11% of the northern sample of 64 PNN) which are too faint to be observed at present.

We present spectral descriptions based on high-resolution spectrograms of central stars of planetary nebulae, obtained with the ESO 3,6-m telescope + CASPEC (Cassegrain Echelle Spectrograph). We make preliminary determinations of stellar photospheric metal abundances, using non-LTE model atmospheres and non-LTE line formation calculations.

The first order moment of P Cygni line profiles has been computed for the case of resonance doublet and subordinate line transitions, using realistic velocity and opacity distributions. This improved method has allowed us to rederive mass-loss rates for a sample of 17 PNN observed in the low resolution mode with IUE. The average value of our mass-loss rates amounts to 10−7 M⊙/yr.

Observed P-Cygni line profiles in the UV spectra of central stars of Planetary Nebulae (PNN) obtained with the IUE satellite has been fitted by theoretical profiles in order to determine mass loss rates.

The past few years have seen the study of Magellanic Cloud planetary nebulae cease to be an extragalactic sideshow and instead become one of the most quantitative branches of planetary nebula research, due largely to our ability to fully exploit the known distances to these systems since the launch of IUE and the advent of sensitive digital detectors mounted on large optical telescopes.

Planetary nebulae can be used to estimate the distances to galaxies and to measure stellar dynamics in faint halos. We discuss surveys which have netted a total of 665 candidate planetary nebulae in NGC 5128 (Cen A), NGC 5102, NGC 3031 (M81), NGC 3115, three galaxies in the Leo Group (NGC 3379, NGC 3384, NGC 3377), NGC 5866, and finally, in NGC 4486 (M87). Radial velocities of planetaries in M32 have shown that its halo velocity dispersion is most likely isotropic. Radial velocities of planetaries in M31 show that ∼ 2/3 of the nebulae with projected radii between 15 and 30 kpc are members of a rotating thick disk with slight asymmetric drift, while ∼ 1/3 belong to a slowly rotating halo. Velocities of 116 nebulae in NGC 5128 reveal pronounced rotation and a slowly declining velocity dispersion in the halo out to 20 kpc. The [O III] λ5007 luminosity functions (PNLFs) in NGC 5128, M81, and the three Leo Galaxies have the same shape over the first magnitude. The highly consistent distances derived from the brightnesses of the jth nebula and the median nebula in different fields in the same galaxy and from different galaxies in the same group lend strong support to the suggestion that planetaries are an accurate standard candle in old stellar populations. Comparison of theoretical luminosity functions to the observed PNLFs shows that there is a very small dispersion in the central star masses.

Our general method for finding planetary nebulae (PN) is to make wide field objective-prism or objective-grating low-dispersion spectra on photographic plates, PN stand up amongst other emission-line objects either as Hα + [N II] 6548-6583 A emitters or as [O III] 50007 A emitters with faint or no continuum, higher-resolution spectroscopy is used for confirming a selection of candidates.

The radial velocities of a total of 94 Planetary Nebulae (PN) in the Large Magellanic Cloud (LMC) have been determined. The kinematics of the population of planetary nebulae is compared with the H I data in the context of a re-analysis of the survey by Rohlfs et al. (1984), taking into account the transverse velocity of the LMC. We find that the best solution for this transverse velocity is 275±65 km s−1, and that the LMC is near perigalacticon. This is consistent with a maximum Galactic mass of order 4.5 × 1011M⊙ out to 51 kpc the rotation curve obtained after correction for this velocity implies a mass of (4.6 × 0.3) × 109 M⊙ within a radius of 3 degrees, or about 6 × 109 M⊙, total. The rotation solution for the PN population is essentially identical with that of the H I, but the vertical velocity dispersion of 19.1 km s−1 is much greater than the value of 5.4 km s−1 found for the H I. This increase in velocity dispersion is consistent with it being the result of orbital heating and diffusion operating in the LMC in a manner essentially identical with that found for the solar neighbourhood.

Spectrophotometry data of the planetary nebula N 66 (WS 35) has been obtained with the CTIO 4-m telescope equipped with an R-C spectrograph and a 2D-Frutti detector. The spectral range between 3700 A and 6800 A was covered at 4 A resolution.

Optical spectroscopic data for 71 Planetary Nebulae (PN) in the Large and Small Magellanic Clouds have been analysed. The line fluxes have been used to determine nebular temperatures, densities, and the abundances of He, N, O, Ne and Ar, relative to H. In our sample there are 12 nebulae with N/O ≥ 0.5, resembling Peimbert's Type I PN; 6 low excitation (LE) objects (1 ≤ I(5007)/I(Hβ) ≤ 4); and 4 very-low-excitation (VLE) nebulae (I(Hβ) > I(5007), similar to the Galactic VLE class. Mean abundances have been calculated for the nebulae not in these special groups.

AAT and IUE spectra of thirteen medium-excitation Magellanic Cloud planetary nebulae have been used to derive H I Zanstra effective temperatures and surface gravities for the central stars.

New evolutionary correlations have been discovered to apply to the population of Planetary Nebulae (FN) in the Magellanic Clouds. Firstly, the age of the nebular shell is found to follow a relationship τ = 890[(Mneb/M⊙) (Vexp/km s−1)]0,6 yr, which is shown to be consistent with a model in which the total energy of the ionised and swept up gas drives the expansion down the density gradient in the precursor AGE wind. Secondly, a tight correlation is found between the expansion velocity and a combination of the Excitation Class and the Hβ flux. This appears to be determined by the mass of the planetary nebula nuclear star. These correlations provide strong observational support for the idea that the PN shells are ejected at low velocity during the Asymptotic Giant Branch phase of evolution, and that they are continually accelerated during their nebular lifetimes.

Although distances to galactic planetary nebulae are typically uncertain by factors near 2, there appears to be an upper limit to the integrated [O III] λ5007 absolute flux for planetary nebulae. This flux, 1.34 × 10−8 ergs/cm2/sec for a maximally bright planetary nebula at a distance of 1 kpc, can be used as a distance indicator when a sufficient number of planetaries have been identified in an external galaxy. Or one may compute the upper limit to the distance for galactic planetary nebulae based on this calibration.

We briefly review the history of the search for progenitors of planetary nebulae starting with Shklovsky's (1956) paper. The inner structure of AGB stars (the likely progenitors) is sketched. The (l, b) distributions and the (l, V) distributions (V is the centre of mass radial velocity) of OH/IR stars and of planetary nebulae are compared; it is concluded that, grosso modo, both types of objects belong to the same galactic population and that most OH/IR stars develop ultimately into planetary nebulae. From a comparison of the properties of OH/IR stars and of Mira variables it is concluded that both are AGB stars with the OH/IR stars having developed from Mira variables. Most OH/IR stars are long period variables but the few that are not are probably transition cases -no longer AGB stars and very early planetary nebulae. It is argued that the IRAS catalog contains a large number of AGB stars without (detected) OH maser emission, but otherwise similar to OH/IR stars. An evolutionary sequence is presented from Mira's to oxygen-rich planetary nebulae. Some speculations are added on the formation of carbon stars and carbon-rich planetary nebulae.

Molecular line observations show that some planetary nebulae are still only partially ionized and are surrounded by the remains of the mass loss envelope shed by the preceding AGB star. The mass loss rates and outflow velocities of these envelopes are similar to those of the cool winds from luminous AGB stars. Both the kinematics of carbon stars and observations of the molecular envelopes around young planetaries show that the carbon star progenitors have a wide range of ages and of mass loss rates. There is increasing evidence that a significant fraction of AGB stars are carbon stars and that these provide a substantial contribution to the total mass returned to the interstellar medium.