In the present poster we suggest that some of the structures observed in the envelopes of planetary nebulae are caused by the interaction of central star wind and radiation with preplanetary nebula debris: planets, moons, minor objects, ring and ring arcs.

It is possible that the magnetic field plays important role in the formation of planetary nebulae(Poscoli, 1992). In order to measure the strength of magnetic field in the envelope of protoplanetary nebulae(PPNe) we have used the Max-Planck-Institut fur Radioastronomie 100-m telescope at Effelsberg to obtain the high frequency resolution and high signal-to-noise ratio 1612 MHz spectra of PPNe, IRAS08005-2356, 18276-1431, and 20406+2953 in both circular polarization. The nature of PPN of these objects are confirmed by Slikhuis et al.(1991), Le Bertre(1987), and Hu et al.(1992) based on the extensive optical, infrared and radio molecular line observations.

Bipolar outflows or polar knots are rather ubiquitous phenomena. A wealth of observational data is now available on bipolar flows associated with young stellar objects or stellar formation regions (Snell, Proc. I. A. U. Symp. Nr. 115, 1987), or nuclei of active galaxies (Asseo and Sol, 1987, Phys. Rep. 148, 307).

High-spatial resolution imaging in the [O III] λ5007 line of a planetary nebula (PN) in the globular cluster M22 reveals a strongly asymmetric (a half-moon shaped) nebular morphology. We confirm that this peculiar morphology is caused by the distortion of stellar ejecta by the ram pressure of the ambient interstellar medium (ISM) through which the cluster is moving with a high velocity of 200 km s−1. Bright emission knots visible in the leading (upstream) nebular section confirm theoretical expectations that the shell should have been fragmented by the Rayleigh-Taylor instability. Stripping of the PN from M22 by the ambient ISM is the first direct evidence for removal of gas from globular clusters. M22 is located at a favourable location for the ram-pressure stripping to be effective, only 400 pc below the Galactic plane, well within a 2 kpc thick layer of ionized gas enveloping the plane. Ionized (possibly neutral) gas in this layer, with a hydrogen density of ∼ 0.1 cm−3, is responsible for the observed interaction.

The galactic Planetary Nebula G 258-15.7 is a large, bright nebula well suited for a detailed study. Known since Wray (1966), its morphology presents several blobs and ansae, generally associated with type I nebulae, and could be described as “late-butterfly” type according to the classification by Balick (1989). The central star has been classified as hydrogen-deficient by Mendez et al. (1985). Spectroscopy of the two main blobs shows a clear overabundance in He and N, with a marginally significant difference between the two sides. The most striking feature is the jet-like structure appearing on the [OIII]/Halpha picture (Fig. 1), the “jets” being located within the main blobs seen on the monochromatic images. A detailed appraisal of all the data will be presented in a subsequent paper.

NGC 6537 is an unusual high excitation bipolar outflow source, with anomalous abundances indicative of a type I nebula. We have recently obtained a range of high resolution spectrophotometry for this source using the 2.5 m Isaac Newton Telescope (Observatorio del Roque de Los Muchachos, La Palma), together with narrow band optical imaging using the 2.6 m Nordic Optical Telescope (Observatorio del Roque de los Muchachos, La Palma). As a consequence, it is apparent that the source optical morphology is suggestive of the presence of an hyperbolic shock outflow surface, similar to those observed in other BPN (e.g. NGC 6302, Hb 5). Line ratio maps also indicate the presence of extremely strong [Nii] emission at the periphery of the outflow, whilst expansion velocities are of order ∼ 400 km sec−1. These large shell expansion velocities may in turn be driven by an extremely high velocity wind, which in this case appears to extend over a range ΔV ≥ 3000 km sec−1.

High-resolution images in [O III] λ5007 of the hydrogen-poor knots of Abell 30 reveal comet-like structures which may be indicative of interaction with the stellar wind. In the near IR, new, higher-resolution, K-band images show an equatorial ring of hot dust that corresponds closely to optical knots 2 and 4 of Jacoby and Ford, while their polar knots 1 and 3 show no comparable IR emission. Both the thermal IR emission and the heavy internal extinction of the central star demands an extremely dusty ejecta. Greenstein showed that the UV extinction curve is fit by amorphous carbon. Our comprehensive dust models consider both the UV extinction and the IR emission from a population of carbon grains. The thermal emission from larger grains produces the far IR emission, while the stochastic heating of very small grains to high temperatures is essential to explain the near IR flux. We are able to reproduce the shape of the near IR spectrum with an a −3.0 distribution of grain radii which extends down to a minimum grain radius of 8 Å.

We present images and high–resolution spectra of the hydrogen deficient knot at the centre of the old planetary nebula A58. The spectra confirm that this region contains essentially no hydrogen, as previously suspected. Emission lines from the knot are broad (FWHM ∼ 180 and 270 km/s for [NII] and [OIII] lines respectively) and are blue–shifted by ∼100 km/s relative to the systematic velocity.

Abell 78 is one of a group of planetaries having an old, H–rich nebula surrounding a hot star which has more recently ejected highly–processed, H–deficient material. The A78 central star has O VI emission lines and a 3700 km s−1 hot wind, and is surrounded by knots of very dusty, H-deficient material. These objects are thought to have suffered a late helium shell flash which resulted in the central star (then a white dwarf) returning to the AGB and ejecting highly-processed material.

The present birthrate of binaries may be written as

where M 1 is the mass of the primary in M ⊙, 0 < q ≤ 1 — mass ratio of components, A — semimajor axis of the orbit in R ⊙. The Eq.(1) implies that all stars are born as binaries with 10 ≤ A/R ⊙ ≤ 106, and that one binary with M 1 ≥ 0.8M ⊙ is formed annually in the Galaxy. We study numerically evolutionary scenarii of binaries within abovementioned range of M 1, A,q. As PN formation events we consider all ejections of common envelopes by close binaries and ejections of envelopes by red giants, after which one may expect a formation of a hot (T e ≥ 30 000K) star, surrounded by a nebula. Altogether about 20 different single and binary cores of PN can be formed. Combining the scenarii data with the Eq. (1) one can estimate the birthrates of most numerous kinds of PNN (single and with main-sequence, white dwarf, giant and relativistic companions) listed in the Table.

A comprehensive spectrophotometric survey of the central stars of planetary nebulae with known or suspected binary star nuclei (BSPN) is underway. The aims of this programme are: to determine the nature of the companion to the ionising star of the nebula; to estimate the spectroscopic distance from the spectral type and magnitude of the companion and thence to determine the luminosity of the hot star; to compare the morphologies and excitation/abundance characteristics of BSPN with those of PN produced by single star evolution. The advantage of the distance determined from this simple method is that it is independent of any assumptions about the planetary nebula, in contrast to most other PN distance estimators.

To date 75 percent of known or suspected BSPN have been observed with the 2.5m Isaac Newton Telescope and the 1.5m ESO spectroscopic telescope at low and intermediate dispersions. A selection of preliminary results from the programme is presented, highlighting the binary central stars of NGC 246 and Abell 65.

Planetary nebula NGC 2346 is a well know butterfly bipolar nebula and the central star (AGK3–O°965) is known to be a spectroscopic binary with a period of about 16 days(1). This object has been observed frequently and no bright variations were noticed from at least 1899 to 1981 Nov(2). But in 1981 an unexpected large amplitude eclipse light variations were observed by Kohoutek(3). Since then a lot of observations have been reported by many authors. They have revealed that the central star V651 Mon showed fast and complex light variations due to eclipse and the amplitudes of the eclipse varied rapidly.

The central star of NGC 2346 is a well known binary with an A-type primary and a hot companion (Méndez and Niemela 1981). The star went through a series of periodic light variations which ceased in 1986 and were interpreted as an eclipse of a dust cloud passing in front of the binary system (e.g. Méndez et al. 1982, Costero et al. 1986). Recently, light variations reappeared with shallower minima compared to the previous eclipse (e.g. Kohoutek et al. 1992).

We have made spectroscopic and photometric observations of two close binary central stars of planetary nebulae HFG 1 (V 664 Cas) and A 63 (UU Sge), using the UH 2.2–m telescope (Mauna Kea Observatory) and the NAO 1.9–m and 0.9–m telescopes (Okayma Astrophysical Observatory).

UU Sge, the eclipsing binary central star (Bond et al, 1978) of the low-surface-brightness planetary nebula (PN) Abell 63, has been observed spectroscopically in the visible throughout its 11.2 hour period and especially during the minimum. A spectral determination of the binary system has been made. The primary hot central star is an ‘O’ type PN nucleus of temperature ≈40,000 K, consistent with the low excitation of the nebular spectrum (e.g. no He ii 4686Å nebular emission detected). From the spectrum at minimum light, the secondary star appears to be a cool dwarf star around G7. Measurement of the magnitude of the secondary during the eclipse of the primary enabled the distance to the PN to be directly determined as 3.6 kpc. For this distance the luminosity of the hot star is approximately 4 320 L⊙, in good agreement with evolutionary tracks for (single) PN nuclei. Deep CCD images of Abell 63 show it has a ‘butterfly’ morphology implying that the close binary central system may have had a strong effect on the nebula shaping. The paper describing this work has been submitted (Walton et al, 1992).

New V and I band CCD photometry and medium resolution spectroscopy are used to derive the masses, luminosities and radii accurate to < 10% for the individual components of the eclipsing central star of the planetary nebula A63–UU Sge (M1 = 0.63 ± 0.06M⊙, R1 = 0.33 ± 0.01R⊙, M2 = 0.29 ± 0.04M⊙ and R2 = 0.53 ± 0.002R⊙). Emission lines from the secondary component and HeII and NV absorption features from the primary component are used to determine the first radial velocity curves of the system. Ultra–violet and optical spectra show that the temperature of the primary compoment is ∼ 105K – much larger than previously suspected. As the techniques used are essentially independent this is probably the most accurately known mass for a planetary nebula central star and therefore allows meaningful comparison to be made with evolutionary tracks for these objects.

We report at first on two old and large planetary nebulae (PN) of which central stars could satisfy the Ritter's criteria (1986) for being precataclysmic binaries: LoTr5 and Abell 35. Both nebulae have probably been ejected as a consequence of common-envelope evolution. A model of cataclysmic binary (CB) for the central star of Abell 35 has been tentatively attempted by Acker and Jasniewicz (1990). The nucleus of LoTr5 is a triple star (Jasniewicz et al., 1987; Malasan et al., 1991): action of a third body on the separation of the close binary could make this binary evolve into a CB (see Mazeh and Shaham, 1979). We report at second on the similarity between the spectrum of the central star of the extended PN HFG1 with that of a CB (Acker and Stenholm, 1990). The PN cited above could be fundamental objects just at the transition between the stage PN and the stage CB.

The nuclei of the low-surface-brightness PNe A 35, LoTr 1, and LoTr 5 are binaries containing rapidly rotating late-type subgiants or giants and extremely hot (T eff ≳ 100,000 K) companions detected by the IUE satellite. All three objects show low-amplitude, periodic photometric variations in the optical band (with periods of 0.76 or 3.3, 6.6, and 5.9 days, respectively).

PC 11 (HD 149427, PK 331-5 1) is classified as a young planetary nebula with strong OIII 4363Å and a Zanstra temperature of TZ = 27000K. It is also classified as (D′ — type) yellow symbiotic star with A — F type companion. It is an IRAS source with detached cold dust with far intrared (IRAS) colours similar to planetary nebulae. The IUE short wavelength (SWP) spectra show emission lines due to OIII] (1661/1666Å). NIII] (1746/1754Å) CIII] (1907/1909Å). The OIII] and NIII] emission lines show significant variation. Variation in the strength of CIII] is not very significant. The strength of OIII] has decreased and NIII] has increased. The long wavelength (LWP) spectrum shows stellar continuum (A-F) and absorption lines due Mg II 2800Å feature. It also show emission lines at 2772Å (?) 3133Å −3140Å (very strong) (OIII, [FeV], 3209Å (He II?) ([FEII]). The variation in the strength of emission line due OIII] and NIII] and the presence of stellar continuum (A-F) suggests that the central star of PC 11 is a binary.

The central star of Sh2–71 was observed with the lm telescope using UBV(RI)c photometric system at Konkoly Observatory in the seasons of 1990–92. A period of 68d.06 was found with variable amplitude and/or lightcurve shape. The amplitude is high, close to 1 magnitude. On the basis of old photographic observations (Kohoutek 1979) this period has not changed during the century. No significant colour variation was detected, but the nebular contamination should distort the colour curves. According to the five colour data the central object is a highly reddened B5 dwarf about 1700 pc distant. The nebular properties, however, indicate an evolved, higher mass, lower luminosity exciting source, therefore it is plausible to regard the central object as a binary. The light variation might be caused by obscuration of the B star by outflowing matter from the true nucleus. Bipolar outflow of 3″ dimension has been detected on high dispersion Hα spectra of the central star (Sabbadin et al. 1985; Cuesta et al. 1990). Further spectroscopic observations are highly needed in order to find the exact description of the system.