We report the detection of nebular emission lines in the optical and mid-infrared spectra of IRAS 17347–3139, a heavily obscured OH/IR star which may be rapidly evolving from the AGB to the PN stage. The presence of emission lines is interpreted as a clear indication that the ionization of its circumstellar envelope has already started. This source belongs to the rare class of objects known as ‘OHPNe’ displaying both OH maser and radio continuum emission. However, unlike the rest of stars in this class, prominent C-rich dust features are detected in its mid-infrared spectrum, which makes the analysis of this star particularly interesting.

We present preliminary results from the first X-ray gratings spectrometer observations of a planetary nebula (PN). We have used the Chandra X-ray Observatory Low Energy Transmission Gratings Spectrometer (LETGS) to observe the bright, diffuse X-ray source within the well-studied BD +30°3639. The LETGS spectrum of BD +30°3639 displays prominent and well-resolved emission lines of H-like C, O, and Ne and He-like O and Ne. Initial modeling indicates a plasma temperature $T_X \sim 2.5\times10^6$ K and abundance ratios of C/O $\sim20$, N/O $\stackrel{<}{\sim}1$, Ne/O $\sim4$, and Fe/O $\stackrel{<}{\sim}0.1$. These results suggest that the X-ray-emitting plasma is dominated by the shocked fast wind from the emerging PN core, where this wind gas likely originated from the intershell region of the progenitor asymptotic giant branch star.

Planetary nebulae are useful kinematic tracers of the stars in all galaxy types. I review recent observationally-driven developments in the study of galaxy mass profiles. These have yielded surprising results on spiral galaxy disk masses and elliptical galaxy halo masses. A key remaining question is the coupling between PNe and the underlying stellar populations.

We have observed the bipolar post-AGB candidate OH 231.8+4.2, using the mid-infrared interferometer MIDI and the infrared camera with the adaptive optics system NACO on the Very Large Telescope. The NACO images at 2.12 and 3.8 $\mu$m show a bipolar outflow and a flared disk or torus. An unresolved core ($<$200 mas in FWHM) is found at the centre of OH 231.8+4.2 in the 3.8 $\mu$m image. This compact source is resolved with the interferometer. The fringes from the four baselines consistently show the presence of a compact circumstellar material with an inner radius of 30–40 mas, which is equivalent to 40–50 AU at 1.3 kpc. This clearly shows that the mid-infrared compact source is not the central star (3 AU) but circumstellar material.

The results of long term observations of photometric ($UBV$) and spectral variability of several PNe are presented. For the most variable nebulae, IC 4997 and NGC 6572, showing both photometric and spectral changes in time, the main physical parameters ($T_{e}$, $N_{e}$ and $T_{*}$) and their time variations were estimated and discussed.

We present a $K\prime$-band speckle image and $HK$-band polarimetric images of the proto-planetary nebula Frosty Leo obtained using the 6 m SAO telescope and the 8 m Subaru telescope, respectively. Our speckle image revealed clumpy structures in the hourglass-like bipolar nebula. The polarimetric data, for the first time, detected an elongated region with small polarizations and polarization vector alignment on the east side of the central star. We have performed radiative transfer calculations to model the dust shell of Frosty Leo. We found that micron-size grains in the equatorial dense region and small grains in the bipolar lobes are required to explain the total intensity images, the polarization images, and the spectral energy distribution.

We present the results of time-resolved photometry and spectroscopy of the central star of the planetary nebula NGC 6026 and time-resolved photometry of the central star of the planetary nebula NGC 6337. The results of period analysis give an orbital period of 0.528088 days for NGC 6026 and a photometric period of 0.173474 days for NGC 6337. In the case of NGC 6337 it appears that the photometric period accurately reflects the orbital period and that the variability is the result of an irradiated hemisphere on the cool companion. For NGC 6026 however, radial velocities from spectroscopy show that the orbital period is twice the photometric period. In this case, the photometric variability is due to an ellipsoidal effect in which one of the stars fills, or nearly fills, its Roche lobe. Based on the data and modeling using the Wilson-Devinney code, we discuss the physical parameters of the two systems. We also relate the physical parameters to the shape and orientation of the nebulosity.

We present Spitzer/MIPS far-infrared (FIR) mapping of O-rich AGB star, R Hya.

Molecular line emission in the mm- and submm-wave domains is found to be a very useful tool to study planetary nebulae (PNe). Molecular lines, particularly the low-$J$ transitions of carbon monoxide, are known to probe most of the nebular material in young PNe and protoplanetary nebulae (PPNe). Many quantitative results on these objects have been so obtained, including general structure, total mass and density distribution, kinetic temperatures, velocity fields, etc. In more evolved PNe, however, the molecular line intensity (or even detection) is quite uncertain, due to photodissociation. Molecular lines often trace just certain parts of these nebulae, like equatorial tori or axial clumps. Other molecules are in general more affected by photodissociation than CO, but photo- or shock-induced chemistry produces high abundances of radicals and large molecules in some intermediate-evolution objects. The presence of rotating disks in some objects is finally discussed.

While photoionization codes have been carefully intercompared, a fundamental need for clean tests against real nebulae remains. NGC 2610 is a high-excitation planetary nebula which, even at HST resolution, is smooth and symmetric. Helium is He$^{++}$ throughout this nebula, which has a high electron temperature (20,000 K) resulting in strong UV lines. It is the best object we know of to test the performance of photoionization codes without the complication of low ionization knots or filaments. Its large angular diameter (40$\prime\prime$) allows spatial gradients to be observed. In 2001 and 2003, we obtained HST STIS long-slit observations to test against models. Observed lines cover wavelengths from 1240Å to 6563Å. Interstellar reddening is small.

We have constructed photoionization models of this nebula, and compare one with our observations. Most lines are in good agreement. The most discordant line is [Ne IV] $\lambda$2424, which is observed to be twice as strong as predicted. Collisional excitation of H$^0$ is the most important coolant, responsible for 30% of the total. Observations of the Balmer decrement in this nebula can put useful constraints on H$^0$ collision strengths.

We have observed SBS 1150+599A spectroscopically in the UV using HST to derive C/H $\sim$ 7.6 and N/H $\sim$ 7.0 for the first time. The central star temperature is now better constrained to $\sim$130,000K, but still is not well determined. This uncertainty dominates the error in O/H, which has been the subject of debate, yet with these data, SBS 1150+599A has the lowest O/H of any PN. Furthermore, the physics of this object are so extreme that minor differences in atomic modeling impact the composition analysis strongly. We also find that the binary central star, based on photometric and kinematic variations, exhibits CV-like properties with an amplitude of 13% and an orbital period of 3.924 hours.

Despite many studies, the post-AGB phase is still not well understood. To make progress in this field, we searched for information about proto-planetary nebulae and built a catalogue of post-AGB objects. Based on collected data we were able to trace the evolution of stars in their late stages making a distinction between carbon and oxygen-rich objects. We focused our attention on spectral features seen in ISO data and clues for AGB nucleosynthesis. Together with the newest HST images of post-AGB objects we can study correlations between morphological types and chemical and physical properties of stars to improve our understanding of stellar evolution.

Historically, Planetary Nebula research has been a ground for much development in atomic physics. In the last five years the combination of a generation of powerful observatories, the development of ever more sophisticated spectral modeling codes, and important efforts on mass production of high quality atomic data have led to important progress in our understanding of the atomic spectra of PNe. In this paper I review such progress, including identification of heavy species (beyond the iron peak elements), observations of hyperfine emission lines and analysis of isotopic abundances, fluorescent processes, and new techniques for diagnosing physical conditions based on recombination spectra. Finally I discuss the new trends on the research of atomic processes in PNe.

We present a powerful new tool to disentangle the 3-D geometry and kinematic structure of gaseous nebulae. The method consists of combining commercially available digital animation software to simulate the 3-D structure and expansion pattern of the nebula with a dedicated, purpose built rendering software and graphical user interface that produce the final images and long slit spectra which are compared to the real data.

The Local Group (LG) represents the best environment to study in detail the PN population in a large number of morphological types of galaxies. The closeness of the LG galaxies allows one to investigate the faintest side of the PN luminosity function and to detect PNe also in the less luminous galaxies, the dwarf galaxies, where a small number of them is expected.

A review of the results of the most recent imaging surveys in the LG is presented. Some applications of the surveys for PNe to the study of the star formation history of the host galaxies are analyzed. In addition, these new observational data are an invaluable resource for follow-up spectroscopy to derive the chemical properties of not only PNe, but also other important emission-line sources like HII regions. These are fundamental tools for the discussion of the chemical evolution of the host galaxies, mapping the history of their chemical enrichment at different epochs. The latest results on this subject are presented.

The San Pedro Mártir Kinematic Catalogue of Planetary Nebulae aims at providing detailed kinematic information for galactic planetary nebulae (PNe) and bright PNe in the Local Group. The database provides long-slit, Echelle spectra and images where the location of the slits on the nebula are indicated. As a tool to help interpret the 2D line profiles or position-velocity data, an atlas of synthetic emission line spectra accompanies the Catalogue. The atlas has been produced with the code SHAPE and contains synthetic spectra for all the main morphological groups for a wide range of spatial orientations and slit locations over the nebula.

The determinations of element abundances in red-giant stars and in particular in AGB stars are reviewed and the resulting abundances are compared with those obtained for planetary nebulae in the Galaxy and in nearby galaxies. The problems, possibilities and implications of such comparisons when estimating yields from low-mass and intermediate-mass stars are illustrated and commented on.

We are currently undertaking a systematic search of new Galactic planetary nebulae (PNe) in the IPHAS (INT Photometric H-Alpha Survey) data. We employ two methods to search for PNe of different sizes: a visual search through continuum subtracted H-Alpha mosaics for extended PNe and a (point) source catalog based search for small diameter PNe. Here we present the methodology and first results of the small diameter PNe search.

We identify emission lines of post-iron peak elements in very high signal-to-noise spectra of a sample of planetary nebulae. Analysis of lines from ions of Kr and Xe reveals enhancements in most of the PNe, in agreement with theories of $s$-process in AGB stars. Surprisingly, we did not detect lines from Br even though $s$-process calculations indicate that it should be produced with Kr at detectable levels.

We present the results of a high-resolution H$_2$ imaging and spectroscopic study of four bipolar proto-planetary nebulae: IRAS 16594–4656, Hen 3-401, Rob 22, and IRAS 17150–3224. These reveal the locations and kinematics of the H$_2$ emission and the shaping of the nebulae by their collimated fast winds.