We report preliminary results of a spectral line survey of NGC 7027 in the $\lambda$ 3 mm and 1.3 mm bands using the Arizona Radio Observatory (ARO) 12-m and 10-m telescopes. To a sensitivity limit of $\sim$10-20 mK, we have detected 34 lines, including hydrogen recombination lines and rotational transitions of CN, CO, CCH, CO$^+$, HCO$^+$, and their isotopes.

We developed a new quick pseudo-3D photoionization code based on Cloudy (Ferland et al.) and IDL (RSI) tools. The code is running the 1D photoionization code Cloudy various times, changing at each run the input parameters (e.g. inner radius, density law) according to an angular law describing the morphology of the object. Then a cube is generated by interpolating the outputs of Cloudy. In each cell of the cube, the physical conditions (electron temperature and density, ionic fractions) and the emissivities of lines are determined. Associated tools (VISNEB and VELNEB_3D) are used to rotate the nebula and to compute surface brightness maps and emission line profiles, given a velocity law and taking into account the effect of the thermal broadening and eventually the turbulence. Integrated emission line profiles are computed, given aperture shapes and positions (seeing and instrumental width effects are included). The main advantage of this tool is the short time needed to compute a model (a few tens of minutes).

We have studied the emission from the core of the Butterfly Nebula. We have tried to interpret the Balmer line profiles, double lines in emission. These profiles are not only observed in M2-9, but are also present in other objects of similar morphology.

During an ongoing search for small planetary nebulae in the southern hemisphere 24 candidates have been found and spectroscopically observed in a region of 45 square degrees.

We report on the progress of our on-going campaign to monitor the evolution of the VLTP objects V4334 Sgr and V605 Aql, as well as the suspected (V)LTP object CK Vul. V4334 Sgr does not show signs of increased ionization compared to our previous observations in 2004. We obtained the first radio detection of V605 Aql, indicating a strong increase in radio flux since 1987. We also present the first radio detection of CK Vul and discuss the expansion of the material ejected during the 1670 event.

Using the [O III] 5007 Planetary Nebula Luminosity Function (PNLF) distance indicator, we can double the number of known distances to nearby Type Ia SNe, and hence improve their zero point calibration while searching for systematic offsets in SN Ia luminosities between young populations (spiral galaxy) and old populations (ellipticals). We report three new PNLF distances and two new lower limits for five galaxies (NGC 524, 1316, 1380, 1448, & 4526) that have hosted well-observed Type Ia SNe. From the PNLF, we find a Hubble constant of 75 km/s/Mpc, whereas we derive H$_0$=72 from Cepheids and H$_0$=73 from SBF.

A better understanding of the nature of the molecular and ionized gas envelopes of planetary nebulae (PNe) is important both to our understanding of their contribution to the ISM and to the evolution of PNe themselves. Using HST's unprecedented resolution and sensitivity for near-IR observations, we are studying the distribution and intensity of molecular gas emission from PNe.

Hydrodynamical simulations played an important role in understanding the dynamics and shaping of planetary nebulae in the past century. However, hydrodynamical simulations were just a first order approach. The new millennium arrived with the generalized understanding that the effects of magnetic fields were necessary to study the dynamics of planetary nebulae. Thus, B-fields introduced a whole new number of physical possibilities for the modeling. In this paper, we review observational work done in the last 5 years and several works on the magnetohydrodynamics of proto-planetary nebulae, since all the effort has been focused on that stage, and discuss different scenarios for the origin of magnetized winds, and the binary-bipolarity relation.

We present 0.18$^{\prime\prime}$ resolution mid-infrared images of OH231.8+4.2 using the Gemini South telescope. The images show a bright central core of $\sim$1$^{\prime\prime}$ in size, with extended emissions in the lobes. We find evidence for different chemical composition of the dust in the core and the lobes from the narrow-band images.

The high-excitation planetary nebula NGC 7009 and its central star were observed with the Far Ultraviolet Spectroscopic Explorer (FUSE) through a 30$\,{\times}\,$30 arcsec (LWRS) aperture, and with the HIRS narrow slit (1.25$\,{\times}\,$20 arcsec) to isolate the inner and outer parts of the nebula from the central star. The high-resolution (15 km/s) nebular spectra (910-1187 Å) show strong emission from C III] and permitted transitions of He II N II, N III, S III, S IV, S VI and O VI, with stronger emission closer to the central star. In this paper we present results obtained on the spatial variation of these tracers of highly ionized gas. The hot central star of NGC 7009 is discussed in a separate paper by Sonneborn et al.

We have recently (Gonçalves et al. 2006) shown that previously reported enhanced N abundances in fast, low-ionization emission regions (FLIERs) of PNe, particularly in NGC 7009, may be due to ionization effects. We reached this conclusion through the 3D MOCASSIN photoionization modeling of the bright inner rim of NGC 7009 and its pair of FLIERs, assuming homogeneous elemental abundances throughout the nebula, for N as well as other elements. The (N$^+$/N)/(O$^+$/O) ratio predicted by our models is 0.60 for the rim and 0.72 for the knots, clearly in disagreement with the N$^+$/N=O$^+$/O assumption of the ionization correction factors (ICF) method. Therefore the ICFs are underestimated in both components, rim and knots, but more so in the knots. This effect is partly responsible for the apparent N overabundance claimed for FLIERs.

Based on the above results we are also investigating what would be the effect of the N/O ICF overestimation on the definition of Type I PNe which do not have FLIERs-like structures.

We report on our recent efforts to compute the X-ray emission from the hot, shocked stellar wind gas filling the inner cavity of planetary nebulae. To this end, we updated our 1D hydrodynamics code NEBEL by including a module that computes the heat transfer by thermal conduction across the contact discontinuity separating the hot shocked wind gas from the much cooler nebular material. Given the temperature and density structure of the hot bubble the X-ray emission is computed by means of the CHIANTI code. We find a reasonably close agreement of the computed X-ray luminosities with recent observations of Newton-XMM and Chandra. Our simulations also predict how the X-ray emission depends on the wind luminosity and the stellar parameters.

New results on the time variation of the radial abundance gradients in the galactic disk are presented on the basis of four different samples of planetary nebulae. These comprise both smaller, homogeneous sets of data, and larger but non-homogeneous samples. Four different chemical elements are considered, namely, O, S, Ar, and Ne. Other objects such as open clusters, cepheids and HII regions are also taken into account. Our analyses support our earlier conclusions in the sense that, on the average, the radial abundance gradients have flattened out during the last 6 to 8 Gyr, with important consequences for models of the chemical evolution of the Galaxy.

We present Spitzer/IRS spectra of a small sample of galactic OHPNe. This is a rare class of transition sources displaying both radio continuum and OH maser emission at 1612 MHz. Our observations show that they are heavily obscured O-rich stars whose mid-infrared spectra are dominated by the simultaneous presence of strong and broad amorphous silicate absorption features together with crystalline silicate emission features which sometimes appear also in absorption. Three of the sources observed are non-variable, confirming their post-AGB status, while another two seem to be still strongly variable. We propose that OHPNe represent the youngest population of high-mass PNe in the Galaxy.

The extreme carbon star, AFGL 3068, is losing mass at a rate in excess of 10$^{-4}$ M$_{\odot}$ yr$^{-1}$, and has so far been detected only in the infrared because it is hidden by a thick dust photosphere having a color temperature of $\sim$300K. Using the ACS camera on HST, we have imaged AFGL 3068 with broad-band filters at 0.6 and 0.8 $\mu$m and find a thin, apparently continuous spiral arc winding 4 or 5 times around the location of the star, from angular radii of 2 to 10 arcsec. We interpret this as the projection of nested spiral shells such as were predicted to occur when the mass-losing star is a member of a binary system. In this case, the illumination is presumably provided by ambient galactic starlight. Subsequent near-IR observations with the NIRC2 camera on the Keck II telescope using adaptive optics reveal that AFGL 3068 has two components separated by 0.11 arcsec, or 109 AU at a distance of 1 kpc. One very red component is presumably the mass-losing carbon star, while the other component is apparently a much bluer companion. Assuming each component has mass M(M$_{\odot}$), and ignoring the projection of the separation vector, we find the binary period to be 810 M$^{-0.5}$ yrs, strikingly comparable to the 710-yr separation of the shells obtained from the known outflow velocity of 14.7 km s$^{-1}$.

High-resolution 905-1187Å spectra of the central star of NGC 7009 obtained with the FUSE satellite provide new constraints on the mass loss and atmosphere parameters. The most prominent spectral feature is a very strong P-Cygni profile of O VI 1032-1038. The only other wind lines are S VI 933-44 (FUSE) and N V 1238-42 and O V 1371 from IUE spectra. C IV 1548-50 and P V 1118-28 are not present, indicating that the wind is very highly ionized. A lower limit on the mass loss rate ($\dot{M}>10^{-8} M_{\odot} $y$^{-1}, v_{\infty}=2450$ km s$^{-1}$) has been derived from an SEI analysis of these wind lines. Preliminary identification of several photospheric spectral features include several strong Fe VII and O VI lines between 1100 and 1170 Å.

Mass loss on the Asymptotic Giant Branch provides the origin of planetary nebulae. This paper reviews several relevant aspects of AGB evolution: pulsation properties, mass loss formalisms and time variable mass loss, evidence for asymmetries on the AGB, binarity, ISM interaction, and mass loss at low metallicity. There is growing evidence that mass loss on the AGB is already asymmetric, but with spherically symmetric velocity fields. The origin of the rings may be in pulsational instabilities causing mass-loss variations on time scales of centuries.

We present ELSA, a new modular software package, written in C, to analyze and manage spectroscopic data from emission-line objects. In addition to calculating plasma diagnostics and abundances from nebular emission lines, the software provides a number of convenient features including the ability to ingest logs produced by IRAF's splot task, to semi-automatically merge spectra in different wavelength ranges, and to automatically generate various data tables in machine-readable or LaTeX format. ELSA features a highly sophisticated interstellar reddening correction scheme that takes into account temperature and density effects as well as He II contamination of the hydrogen Balmer lines. Abundance calculations are performed using a 5-level atom approximation with recent atomic data, based on R. Henry's ABUN program. Downloading and detailed documentation for all aspects of ELSA are available at the following URL:

We present our recent results of the high dispersion spectroscopy of a Galactic halo planetary nebula, K 648, in the globular cluster M 15. The position-velocity diagrams of our spectra indicate the existence of collimated outflows in K 648. In the [N II$\lambda$6583 diagram, we found high velocity components with a velocity $\sim$60 km s$^{-1}$ in the central region of K648.

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.