Determinations of the plasma diagnostics and chemical compositions of planetary nebulae require ultimately high dispersion spectra. For objects of high surface brightness the Hamilton Echelle Spectrograph at Lick Observatory is satisfactory for the region 3650–10100Å which involves the 168th to 56th echelle orders. For a slit width of 640 μm amounting to 1.15 arcsec at the Coude focus, the actual spectral resolution (FWHM) is about 0.2Å at 8850Å. The length of the slit is chosen as 4.0 arcsec. Hyung (1994) & Aller (1994) describe the observing procedure. Since the Hamilton echelle was designed primarily for star-like sources, it is not useful for extended low surface brightness PN. The earlier observations were obtained with an 800 × 800 chip that did not cover the echelle field, so several settings were needed. Later, we used a slower 2048 × 2048 chip which covered the whole field and was somewhat more efficient at longer wavelengths. The program has been completed and definitive measurements have obtained for NGC 2440, NGC 6543, NGC 6741, NGC 6818, NGC 7026, NGC 7662, and Hu 1-2. All of these PN display particularly rich, interesting spectra. Previously observed and published objects include IC 351, IC 418, IC 2149, IC 4997, NGC 6567, NGC 6572, NGC 6790, NGC 6886, NGC 7009, BD +30 3639, & Hubble 12. NGC 6884 is in press. Additional nebulae which are yet to be discussed are IC 4634, IC 4846, IC 5117, NGC 6210, & NGC 6803.

Jacoby & Fullton (1994, BAAS, 26, 1384) searched 133 of the ∼ 150 Galactic globular clusters for Planetary Nebulae (PNe) using the on-band/off-band imaging technique at [O III] λ5007Å. We present preliminary abundances and central star properties for the 2 new PN identified in that survey (labeled JaFu 1 and JaFu 2 by Acker, Marcout, & Ochsenbein 1996).

A variety of compact nebulae was observed to retrieve the morphology in the light of infrared recombination lines ([Siv] at λ = 10.5μm and [Neii] at λ = 12.8μm) using TIMMI, ESO's focal reducer for the thermal infrared at the 3.6m telescope (Käufl et al. 1994). Compared to optical images in some cases striking differences are found. It should be noted that the dust in nearly all PNs is transparent at λ ≈ 10μm even if there is substantial extinction in the optical (λ ≤ 1μm). As compared to space based infrared platforms (IRAS and ISO) our observations have lower sensitivity but sub-arcsec spatial resolution. In some cases the data allow also to assess the relative spatial distribution of dust and gas.

The evolution of planetary nebulae is controlled largely by hardening of the radiation field from the central star and by hydrodynamic interactions between the “fast wind” and the slower red giant wind. These processes also result in the heating and dissociation of H2 and in the production of H2 vibration–rotation lines in the near-infrared. Both mechanisms tend to produce high gas temperatures and, at high densities, a thermal population of states. Kinematic studies provide vital information on the geometry and expansion of the nebulae and offer a discriminant between shocked and photodissociated regions.

The Infrared Space Observatory (ISO) has to be regarded as the most powerful infrared facility that has ever been available to the astronomical community. In order to fully exploit the wealth of information contained in ISO data, one has to supplement the satellite observations with a ground-based campaign. In collaboration with the Kiel group, our group in Innsbruck is carrying out two observing programs with ISO. Our observations aim at the study of hot dust in bipolar PNe seen edge-on and in so-called “born-again” PNe.

The carbon, nitrogen and oxygen abundances in the Planetary Nebulae (PN) derived from the optical recombination lines are usually much larger than those determined from collisional excited UV, IR and optical lines. This discordance is the bright evidence for PN to be strongly inhomogeneous. Starting with consideration by Peimbert (1967) we have been working out the code for calculation the nebular line intensities taking into account both temperature and density fluctuations.

Information in Astronomy is available in multiple form. There are the periodicals as well as printed catalogues. Electronic abstract and paper services as well as general data centers as provided by NED, CDS, NASA/ADC, STScI, … and give access via modern communication media. The Deep Near Infrared Southern Sky Survey consortium (DeNIS, Epchtein et al. Astrophys. and Space Sci., 217, 3) itself provides all the survey data at two dedicated centers. Regarding all these services we have to ask:

Two ISO projects of scientists in Innsbruck deal with spatially resolved investigations of planetary nebulae in the infrared. Imaging in the NIR (1.0–2.4μm) is not possible with ISO and the spatial resolution and the limiting flux of the new surveys (DeNIS and 2MASS) will be insufficient for most of our objects.

We present abundances derived from echelle spectroscopy of the planetary nebula NGC 6210 from the forbidden, collisionally excited lines, and from the permitted, recombination lines. We have obtained spectra from 3 positions in the nebula: at the central star, and 6 and 12 arcseconds south of the central star. We find a discrepancy of a factor of 2 between the O2+/H+ ratio derived by the recombination lines and by the forbidden lines in each spatial position. This discrepancy may result from the presence of temperature fluctuations in NGC 6210, where the collisionally excited lines are exponentially weighted to regions of higher temperature. A value for the root-mean-square temperature fluctuation parameter t2(OIIabun)= 0.038+0.007–0.009 is derived for the central star spectrum, 0.040+0.006–0.013 for the 6 arcsecond offset, and 0.051+0.014–0.015 for the 12 arcsecond offset spectrum. Thus no significant variation in t2 is seen as a function of spatial position within the nebula. We have also estimated t2 by comparing the derived Balmer Jump temperature at the 6 arcsecond offset, Te(BaJ)= 7900+2400–1600K, with the temperature derived from the [O III] 5007/4363å ratio Te[O III]= 9370±100K at this position. This comparison suggest t2(BaJ)= 0.041±0.020, in agreement with the values for t2 as estimated from the recombination lines.

The photometric and spectral study of 7 selected planetary nebulae has been carried out since 1968. (See: Mem. Soc. Roy. Sci. Liege, 6e ser., 1973, 5, 473). During nearly 30 years of photoelectric observations, 5 planetaries (NGC 6572, IC 4997, Hu2-1, NGC 6891 and NGC 6543) have undergone noticeable variations of integral UVB-brightness in the range 0.1÷0.6 mag. The nebulae NGC 6720 and IC 3568 showed no changes of integral brightness exceeding 0.1 mag. The most remarkable behaviour was found for the nebula IC 4997: a steady decrease of the integral brightness in 1968–85, amounted on the whole to 0.4 ÷ 0.6 mag., an unexpected stop of this decrease in 1985–86, and almost monotonous brightening in 1987–96.

We observed NGC 6543 (the Cat's Eye Nebula) with the HST WFPC2 camera in ten narrow-band filters covering a range of emission lines. These images are used to further look at the physical conditions in NGC 6543. We discuss the [O III] electron temperature, ionization state throughout the nebula, and the results of photoionization models of individual structures.

We present the first results of a deep near-infrared narrowband imaging study of several planetary nebulae. The data were acquired using the University of Hawaii 2.2m telescope on Mauna Kea and the “QUIRC” 1024 × 1024 array camera. With these sensitive high spatial resolution imaging data, we are able to explore in detail where H2 is found relative to the ionized region in planetary nebulae at various stages of evolution (See Figure 1, for an example). The objects were selected from previous studies to have evidence for extended emission from H2, and they are at several differing phases of central star evolution. The presence of molecules in the UV–flooded environment of a planetary nebula cannot be explained without highly non-spherical geometries and high densities, or clumping. Although there can be an ambiguity in the excitation mechanism (UV photons or shocks), the location of H2 emission identifies regions of the nebula with sufficient dust shielding and density for the survival of molecular species. The emission morphology also provides information that helps identify which excitation mechanism is most likely. When combined with data provided by other molecular studies, we can examine how the photodissociation region evolves through the circumstellar envelope as the planetary nebula tracks across the top of the HR diagram. We can also consider how morphological evolution of the nebula, through interacting winds and shocks, might provide the conditions necessary for molecular survival.

Spatially resolved profiles of the Hα, and [NII] lines have been obtained with the Manchester echelle spectrometer combined with the 2.1 m San Pedro Mártir telescope over the bipolar lobes, the symmetric low ionization knots and the bright core of the planetary nebula KjPn 8. The lobes of this galactic bipolar nebula have the largest angular extent, 14′ × 4′, yet discovered.

We report sub-arcsecond narrow band imaging in the lines of H2 2.1218 μm, Brγ 2.16 μm, [Fe II] 1.664 μm of the Planetary Nebulae NGC 7027. Data were obtained at the 3.5 m telescope at Calar Alto Observatory (Spain), using MAGIC. A false color image was produced by combining these three narrow band images. Thus, and due to extraordinary seeing (0″.6 arcsecond) conditions, allow us to reveal the morphology of the excited molecular and ionized gas. The Brγ and the [Fe II] images allowed us to study the structure of the ionized gas at slightly different excitation levels, according to the ionization potentials of the ions involved in the corresponding transitions (13.6 eV to ionize hydrogen, versus 17.4 eV for iron ionizaton). Since NGC 7027 is a high excitation nebula, the iron is readily double– ionized in the hotter regions, thus what we really see in the [Fe II] image is the low–intermediate excitation zones. By studying the [Fe II] and Brγ images together we infer that: the (non–reddened) low–ionization gas morphology consists of a regular, smooth ring reminder of a projected cylindrical structure. In addition to a brightness level that is at least thirty times the brightness of the maximum [Fe II] emission, the ionized hydrogen image exhibit a strong brightness gradient between the mentioned ring and the outer regions, and the emission is comparatively negligible outside the ring–like feature of about 12 × 10 arcsec (the measures refer to the major and minor axes of the ellipse–like shape). The [Fe II] morphology is less so ring–like and regular, and it seems to indicate smaller scale structure, such as clumps and filaments, at the resolution scale–level. The dishomogeneity in the [Fe II] emission could be ascribed to gradients in the elemental distribution, as well (and more probably so) as to the plasma temperature and density inhomogeneities. The H2 molecular image completely embeds the ionized gas zones, up to a size of about 16 × 11 arcsec. The smaller size refers here to the waist of the markedly bipolar shape, similar to a projected peanut; the larger size is the dimension of the two main lobes. The highest brightness through the molecular filters corresponds to the inner ring, slightly less extended than the ionized one, and to an outer envelope that is not seen in the ionized gas, and has a maximum diagonal extension of about 24 arcsec. Spatially resolved low resolution spectra (R 200) were obtained in the H and K band.

A semi-analytical model has been constructed to calculate the TP-AGB evolution of low-and intermediate-mass stars (Marigo et al. 1996), starting from the first thermal pulse until the complete ejection of the envelope by stellar winds. We estimate the changes in the chemical composition of the envelope due to different processes: (i) the intershell nucleosynthesis and convective dredge-up; (ii) envelope burning in the most massive AGB stars (M ≥ 3–4M⊙); (iii) mass loss by stellar winds.

Emission lines arising from transitions in S II have been detected in a wide variety of astronomical sources, including planetary nebulae (Hyung, Keyes & Aller 1995). These transitions are used to derive information on emitting plasmas parameters (Te, Ne) through diagnostic line ratios, although to calculate these quantities reliably, accurate atomic data must be employed, especially for electron impact excitation rates.

The 2s21S0–2s2p 3P1 intercombination line at 1218.34 Å of Be-like O V has been observed in IUE spectra of gaseous nebulae such as RR Tel (Doschek & Feibelman 1993). However, the forbidden line at 1213 Å has not been detected to date in any astrophysical object, with the possible exception of the Sun, where Sandlin, Brueckner & Tousey (1977) very tentatively identify the line at 1213.90 Å in an off-limb spectrum.

The nature and origin of the hundreds of ionized knots, with cometary tails, in the Helix planetary nebula are both being unravelled by recent observations. Healey and Huggins (1990, AJ, 100, 511), Meaburn et al (1992, MNRAS, 255, 177) and Walsh and Meaburn (1993, ESO Messenger, 73, 35) all showed, in various ways, that these knots have dense (106 cm–3), dusty, molecular cores with ionized arcs of gas on the surfaces pointing towards the ionizing star. This structure is confirmed in detail by the HST imagery of O'Dell and Handron (1996, ApJ, in press).

The remarkable velocity structure of the different components of the hydrogen deficient planetary nebula Abell 30 have been revealed for the first time by obtaining spatially resolved profiles of the [O III] 5007 å lines with the Manchester echelle spectrometer combined with the 2.1 m San Pedro Mártir telescope.

The are often inconsistencies between the results of different methods for deriving electron temperatures from line strengths in PNe. Temperatures derived from forbidden lines ratios such as [OIII]4363/5007, are on average higher than those calculated from permitted lines. This is normally explained by assuming the existence of areas of higher temperatures which have more weight in a forbidden line analysis, the so-called ‘temperature fluctuations’. The magnitude of these fluctuations is expressed by the t2 parameter. See Peimbert (1967). A typical value is about 0.03, corresponding to fluctuations of ∼ 10%. Photoionization models have difficulty in explaining fluctuations of this magnitude (Kingdon & Ferland 1995).