bluuebunny/crossref_metadata_2025 huggingface dataset:
Historical overview of planetary nebulae research
Authors: Kwok Sun
Published: August 2012

Planetary nebulae (PNs) were first discovered over 200 years ago and our understanding of these objects has undergone significant evolution over the years. Developments in astronomical optical spectroscopy and atomic physics have shown that PNe are gaseous objects photoionized by UV radiation from a hot central star. Studies of the kinematics of the nebulae coupled with progress in theories of stellar evolution have led to the identification that PNe are evolved stars and progenitors of white dwarfs. Development of infrared and millimeter-wave technology in the 1970s made us realize that there is significant amount of neutral matter (molecules and dust) in PNe. The link of PNe to the stellar winds from their progenitor asymptotic giant branch (AGB) stars and subsequent dynamical interactions are now believed to be the underlying causes of the morphological structures of PNe. The role of PNe as prolific molecular factories producing complex molecules and organic solids has significant implications on the chemical enrichment of the Galaxy.

In this paper, we discuss the misconceptions and errors that we have encountered in our journey of understanding the nature of PN. The various detours and dead ends that had happened during our quest to pin down the evolutionary status and causes of nebulae ejection will be discussed. As there are still many unsolved problems in PN research, these lessons of history have much to offer for future progress in this field.
Spitzer IRS spectra of compact Galactic planetary nebulae: The link between dust, evolution, and metallicity
Authors: Stanghellini L. , García-Hernández D. A. , García-Lario P. , Davies J. E. , Shaw R. A. , Villaver E. , Manchado A. , Perea-Calderón J. V.
Published: August 2012

A sample of ~150 compact Galactic PNe has been observed with the Spitzer/IRS spectrograph to characterize their dust properties. These PNe are likely to be at the onset of the PN evolutionary phase, and are therefore ideal for probing dust evolution. The molecular emission features in these Galactic PN spectra are similar to those found in our Magellanic Cloud sample, except that we found a sizable fraction of PNe with mixed-chemistry dust which are not observed in the Clouds. We also found that the distribution among dust types depends strongly on the metallicity of the parent population, implying that the metallicity of the progenitors affects the evolution of a PN from its early stages.
Observational studies of mass loss from AGB stars
Authors: Matsuura Mikako
Published: August 2012

It is important to properly describe the mass-loss rate of AGB stars, in order to understand their evolution from the AGB to PN phase. The primary goal of this study is to investigate the influence of metallicity on the mass-loss rate, under well determined luminosities. The luminosity of the star is a crucial parameter for the radiative driven stellar wind. Many efforts have been invested to constrain the AGB mass-loss rate, but most of the previous studies use Galactic objects, which have poorly known distances, thus their luminosities. To overcome this problem, we have studied mass loss from AGB stars in the Galaxies of the Local Group. The distance to the stars have been independently measured, thus AGB stars in these galaxies are ideal for understanding the mass-loss rate. Moreover, these galaxies have a lower metallicity than the Milky Way, providing an ideal target to study the influence of metallicity on the mass-loss rate. We report our analysis of mass loss, using the Spitzer Space Telescope and the Herschel Space Observatory. We will discuss the influence of AGB mass-loss on stellar evolution, and explore AGB and PN contribution to the lifecycle of matter in galaxies.
Asymptotic giant branch evolution: Where do we stand?
Authors: Marigo Paola
Published: August 2012

I provide a synthetic overview of the present status of stellar models for the asymptotic giant branch phase, one of the most complex and still uncertain stages of stellar evolution. In particular I will focus on two aspects that are most relevant in the context of the planetary nebulæ progeny, namely: the chemical composition of the AGB ejecta, and the mass of the bare CO core left after the ejection of the stellar mantle at the AGB tip. Recent progress, present uncertainties, and future perspectives to constrain AGB models are briefly discussed.
Shaping proto-planetary nebulae by binary systems
Authors: Riera A. , Velázquez P. F. , Steffen W. , Raga A. C. , Cantó J.
Published: August 2012

We present the results of 3D hydrodynamic simulations aimed to explore the binary scenario for shaping bipolar, point- and mirror-symmetric proto-Planetary Nebulae. We consider a jet launched by the secondary star of a binary system, located at the center of the PPN, which propagates within a circumstellar medium swept previously up by the wind of the giant companion. As a result of the presence of the companion star, the accretion disk around the jet source is likely to precess. We have carried out 3D hydrodynamical simulations with the YGUAZÚ-A code including the combination of an orbital motion plus a precession. Our results show that to produce a multipolar nebula, it is necessary to have a precessing jet in a binary system with a time-dependent ejection velocity.
Ongoing surveys for close binary central stars and wider implications
Authors: Miszalski Brent
Published: August 2012

Binary central stars have long been invoked to explain the vexing shapes of planetary nebulae (PNe) despite there being scant direct evidence to support this hypothesis. Modern large-scale surveys and improved observing strategies have allowed us to significantly boost the number of known close binary central stars and estimate at least 20% of PNe have close binary nuclei that passed through a common-envelope (CE) phase. The larger sample of post-CE nebulae appears to have a high proportion of bipolar nebulae, low-ionisation structures (especially in SN1987A-like rings) and polar outflows or jets. These trends are guiding our target selection in ongoing multi-epoch spectroscopic and photometric surveys for new binaries. Multiple new discoveries are being uncovered that further strengthen the connection between post-CE trends and close binaries. These ongoing surveys also have wider implications for understanding CE evolution, low-ionisation structure and jet formation, spectral classification of central stars, asymptotic giant branch (AGB) nucleosynthesis and dust obscuration events in PNe.
Reduce, reuse, recycle: Planetary nebulae as green galactic citizens
Authors: Kwitter Karen B. , Henry Richard B. C.
Published: August 2012

We review gas-phase abundances in PNe and describe their dual utility as archives of original progenitor metallicity via the α elements, as well as sources of processed material from nucleosynthesis during the star's evolution, i.e., C, N, and s-process elements. We describe the analysis of PN spectra to derive abundances and discuss the discrepancies that arise from different choices at each step. Abundance results for the Milky Way and Magellanic Clouds from various groups of investigators are presented; the observational results are compared with theoretical predictions of AGB stellar yields. Finally, we suggest areas where more work is needed to improve our abilities to determine abundances in PNe.
Atomic processes in planetary nebulae
Authors: Liu Xiaowei
Published: August 2012

Progress in the study of the atomic processes in planetary nebulae (PNe) is reviewed, focusing on the literature published since the last IAU symposium on PNe five years ago. High quality photoionization cross sections and recombination coefficients are now available for the first six ions of the trans-iron elements selenium and krypton, enabling robust modeling of their ionization structure and consequently converting the measured ionic abundances to elemental abundances. Major progress has been achieved in utilizing the recombination spectra of helium and heavy element ions to probe the nebular physical conditions. New ab initio, density-dependent effective recombination coefficients have been calculated for the recombination spectra of O ii and N ii, down to very low temperatures (~ 100–300 K). Plasma diagnostics based entirely on those heavy element recombination lines are developed and applied to the observations. It is shown that these heavy element recombination lines originate predominately from cold plasmas of temperatures ~ 1,000 K, in agreement with the predictions of the bi-abundance model that has been proposed to explain the dichotomy of nebular plasma diagnostics and abundance determinations using collisional excited lines (CELs) on the one hand and optical recombination lines (ORLs) on the other.
Magnetic fields during the evolution towards planetary nebulae
Authors: Vlemmings Wouter
Published: August 2012

Magnetic fields appear ubiquitous throughout the envelopes of evolved stars. However, their origin and role in the formation of planetary nebulae is still unclear. As observations of magnetic fields are complicated and time consuming, the observed samples of AGB and post-AGB stars and planetary nebulae are still small. Still, magnetic energy seems to dominate the energy budget out to a distance of several tens of AU from the central star and the field morphology often appears to be well ordered. A short summary is given of the current observations and the potential of new instruments such as ALMA is discussed.
Understanding the immediate progenitors of planetary nebulae
Authors: Sahai R. , Morris M. R. , Contreras C. Sánchez , Claussen M. J.
Published: August 2012

Pre-Planetary Nebulae (PPNe) are believed to represent a relatively short, intermediate evolutionary phase in the evolution of AGB stars to Planetary Nebulae (PNe). Our unbiased, high-resolution imaging surveys with HST of young PNe and PPNe show very strong morphological similarities between these classes, enabling us to extend our morphological scheme for PPN classification to young PNe, preserving virtually all of the primary and secondary descriptors, and adding a few new ones. These morphological surveys show that the primary shaping of PNe begins during the PPNe and/or late-AGB phase, and the key to understanding the shaping process lies in the study of these PNe progenitors. Here we present results from two recent studies of PNe progenitors: (i) Hα emission with very broad wings and P-Cygni profiles as probes of the region where the fast post-AGB outflows that do the shaping are most likely launched from, and (ii) equatorial waists with large-sized dust grains and large masses.
Central stars of planetary nebulae: The white dwarf connection
Authors: Werner Klaus
Published: August 2012

This paper is focused on the transition phase between central stars and white dwarfs, i.e. objects in the effective temperature range 100 000 – 200 000 K. We confine our review to hydrogen-deficient stars because the common H-rich objects are subject of the paper by Ziegleret al. in these proceedings. We address the claimed iron-deficiency in PG1159 stars and [WC] central stars. The discovery of new Neviiand Neviiilines in PG1159 stars suggests that the identification of Oviiand Oviiilines that are used for spectral classification of [WCE] stars is wrong. We then present evidence for two distinct post-AGB evolutionary sequences for H-deficient stars based on abundance analyses of the He-dominated O(He) stars and the hot DO white dwarf KPD 0005+5106. Finally, we report on evidence for an H-deficient post-super AGB evolution sequence represented by the hottest known, carbon/oxygen-atmosphere white dwarf H 1504+65 and the recently discovered carbon-atmosphere “hot DQ” white dwarfs.
Modeling the diffuse X-ray emission of planetary nebulae with different chemical composition
Authors: Steffen Matthias , Sandin Christer , Jacob Ralf , Schönberner Detlef
Published: August 2012

Based on time-dependent radiation-hydrodynamics simulations of the evolution of Planetary Nebulae (PNe), we have carried out a systematic parameter study to address the non-trivial question of how the diffuse X-ray emission of PNe with closed central cavities is expected to depend on the evolutionary state of the nebula, the mass of the central star, and the metallicity of stellar wind and circumstellar matter. We have also investigated how the model predictions depend on the treatment of thermal conduction at the interface between the central ‘hot bubble’ and the ‘cool’ inner nebula, and compare the results with recent X-ray observations. Our study includes models whose properties resemble the extreme case of PNe with Wolf-Rayet type central stars. Indeed, such models are found to produce the highest X-ray luminosities.
Planets, evolved stars, and how they might influence each other.
Authors: Villaver Eva
Published: August 2012

Over the last 20 years planetary searches have revealed a wealth of systems orbiting stars on the main sequence. Most of these low-mass stars eventually will evolve into the Giant phases before entering the planetary nebulae (PNe) stage. In the last years, the presence of planets has also been discovered around more massive evolved stars, mostly, along the Red Giant but also along the Horizontal Branch. Moreover, disks have been found around White Dwarfs presumably formed by tidally disrupted asteroids. In all, there is evidence that an evolved (ing) star might influence the survival of planets. In this review I will try to summarize such evidence but furthermore I will present the other side of the story, that is, how the presence of a planet might alter the evolution of stars and with that the PN formation.
The ionization of galaxies by their planetary nebulae
Authors: Stasińska Grażyna
Published: August 2012

Recent studies have shown that nuclei of planetary nebulae and their remnants (dubbed HOLMES for “hot low-mass evolved stars”) can easily explain two long-standing problems of extragalactic astronomy: the observed emission-line spectra of ellipticals and LINER-like galaxies and the ionization and heating of the diffuse interstellar medium in spirals. They are summarized in this contribution. It is emphasized that the computation of grids of stellar evolution models until the white dwarf stage is essential not only for the study of planetary nebulae but also for the study of the ionization of galaxies.
PNe in NGC 300: Their abundances and chemical gradients
Authors: Peña Miiriam , Stasinska Grazyna , Bresolin Fabio , Tsamis Yiannis
Published: August 2012

Spectrophotometric data of a number of planetary nebulae and compact HII regions of NGC 300 have been obtained with the FORS 2 spectrograph of the VLT. We present a preliminary analysis of such data.
Planetary nebulae populations in external galaxies
Authors: Arnaboldi Magda
Published: August 2012

This review highlights the properties of the planetary nebulae in external galaxies as tracers of light, of the stellar population properties, and of the distances and kinematics of the parent galaxies. Recent results on the kinematics of the outer regions in giant elliptical galaxies and on the luminosity specific PN numbers (the α parameter) in these systems are presented, based on current surveys of planetary nebulae with the Planetary Nebulae Spectrograph (PN.S) and other instruments. Finally a brief discussion is given of planetary nebulae as tracers of the diffuse light in the nearby clusters, such as Virgo and Hydra I.
The frontier of ground-based observations
Authors: Käufl Hans U.
Published: August 2012

The ESO VLT on Paranal is in transition from first generation instrumentation to second generation, or at least to substantially upgraded instrumentation. The new instrumentation shall establish multipicity gain, high image definition or integral field imaging spectroscopy. Starting from observational highlights, status and trends for groundbased instrumentation will be revisited with emphasis on the field of PNe in all evolutionary phases. This review will concentrate on spectroscopy and scientific cases where groundbased observations offer a particular advantage. To the extent possible, a projection will be given as to the potential of the extremely large telescopes on the horizon, which will work best in the (near-)infrared.
Distance mapping technique and the 3-D structure of BD +30°3639
Authors: Akras Stavros , Steffen Wolfgang
Published: August 2012

We present a new kinematic analysis technique called distance mapping. It uses the observed proper motion vectors and the 3-D velocity field to determine the distance for each vector. From this information we generate maps that can be use as a constraint to morpho-kinematic modeling with SHAPE. It is applied to BD +30°3639, using the internal proper motion measurements by Li et al. (2002). We determine its distance at 1.40 kpc ± 0.15 kpc.
Planetary nebulae and their mimics: The MASH-MEN Project
Authors: Boissay Rozenn , Parker Quentin A. , Frew David J. , Bojicic Ivan
Published: August 2012

The total number of true, likely and possible planetary nebulae (PN) now known in the Milky Way is about 3000, approximately twice the number known a decade ago. The new discoveries are a legacy of the recent availability of wide-field, narrowband imaging surveys, primarily in the light of Hα. The two most important are the AAO/UKST SuperCOSMOS Hα survey SHS and the Isaac Newton photometric Hα survey IPHAS, which are responsible for most of the new discoveries. A serious problem with previous PN catalogs is that several different kinds of astrophysical objects are able to mimic PN in some of their observed properties leading to significant contamination. These objects include H~II regions and Strömgren zones around young O/B stars, reflection nebulae, Wolf-Rayet ejecta, supernova remnants, Herbig-Haro objects, young stellar objects, B[e] stars, symbiotic stars and outflows, late-type stars, cataclysmic variables, low redshift emission-line galaxies, and even image/detector flaws. PN catalogs such as the Macquarie/AAO/Strasbourg Hα Planetary Nebula catalog (MASH) have been carefully vetted to remove these mimics using the wealth of new wide-field multi-wavelength data and our 100% follow-up spectroscopy to produce a compilation of new PN discoveries of high purity. During this process significant numbers of PN mimics have been identified. The aim of this project is to compile these MASH rejects into a catalog of Miscellaneous Emission Nebulae (MEN) and to highlight the most unusual and interesting examples. A new global analysis of these MEN objects is underway before publishing the MEN catalog online categorizing objects by type together with their spectra and multi-wavelength images.
Identification of three new protoplanetary nebulae exhibiting the unidentified feature at 21 μm
Authors: Cerrigone Luciano , Hora Joseph L. , Umana Grazia , Trigilio Corrado , Hart Alexa , Fazio Giovanni
Published: August 2012

Since its discovery, the feature at 21 μm has been detected in all C-rich proto-PNe of intermediate spectral type (A–G) and – weakly – in a few PNe and AGB stars, but the nature of its carriers remains unknown. In this paper, we show the detection of this feature in the spectra of three new stars obtained with the Spitzer Space Telescope. In the attempt to relate the unidentified feature to other dust features, we retrieved mid-IR spectra of all the 21 μm sources currently known from ISO and Spitzer archives and noticed a correlation between the flux emitted in the 21 μm feature and that emitted at 7 and 11 μm (PAH bands and HAC broad emission). Such a correlation may point to a common nature of the carriers.
Searching for binary central stars of planetary nebulae with Kepler
Authors: Douchin Dimitri , Jacoby George H. , De Marco Orsola , Howell Steve B. , Kronberger Mattias
Published: August 2012

The Kepler Observatory offers unprecedented photometric precision (<1 mmag) and cadence for monitoring the central stars of planetary nebulae, allowing the detection of tiny periodic light curve variations, a possible signature of binarity. With this precision free from the observational gaps dictated by weather and lunar cycles, we are able to detect companions at much larger separations and with much smaller radii than ever before. We have been awarded observing time to obtain light-curves of the central stars of the six confirmed and possible planetary nebulae in the Kepler field, including the newly discovered object Kn 61, at cadences of both 30 min and 1 min. Of these six objects, we could confirm for three a periodic variability consistent with binarity. Two others are variables, but the initial data set presents only weak periodicities. For the central star of Kn 61, Kepler data will be available in the near future.
Excitation of emission lines by fluorescence and recombination in IC 418
Authors: Escalante Vladimir , Morisset Cristophe , Georgiev Leonid
Published: August 2012

We predict intensities of lines of CII, NI, NII, OI and OII and compare them with a deep spectroscopic survey of IC 418 to test the effect of excitation of nebular emission lines by continuum fluorescence of starlight. Our calculations use a nebular model and a synthetic spectrum of its central star to take into account excitation of the lines by continuum fluorescence and recombination. The NII spectrum is mostly produced by fluorescence due to the low excitation conditions of the nebula, but many CII and OII lines have more excitation by fluorescence than recombination. In the neutral envelope, the NI permitted lines are excited by fluorescence, and almost all the OI lines are excited by recombination. Electron excitation produces the forbidden optical lines of OI, but continuum fluorescence excites most of the NI forbidden line intensities. Lines excited by fluorescence of light below the Lyman limit thus suggest a new diagnostic to explore the photodissociation region of a nebula.
Integral stellar-nebular model of NGC 7009
Authors: Fierro Celia R. , Peimbert Antonio , Georgiev Leonid , Morisset Christophe , Arrieta Anabel
Published: August 2012

We developed a self-consistent stellar-nebular model for NGC 7009. This model reproduces the available observations ranging from optical to UV. The combined approach to the modeling process produces more constraints and thus more trustworty results. After obtaining the model, we perform a comparative study of the chemical composition of He, N, O, Ne, Cl, and S in the nebula and its central star. Concluding that the stellar composition agrees with the nebular composition with t2 ≠ 0.00.
Green's functions for polarized radiative transfer equation in different geometries
Authors: Freimanis Juris
Published: August 2012

A review of some earlier exact analytic solutions of monochromatic stationary vector radiative transfer equation in homogeneous infinite medium is given. It is stressed that Green's functions for plane-parallel, spherical and cylindrical symmetry are expressed through derivatives and integrals from basically one and the same set of functions.
On relation between nebular morphology and infrared photometric properties
Authors: Górny Slawomir K. , Siódmiak Natasza
Published: August 2012

We report on the ongoing study of the infrared properties of different types of planetary nebulae based on the data from recent photometric and spectroscopic infrared surveys. We present our first results concerning the relation between nebular morphology and infrared properties using the observations from the AKARI mission.
Ablation and Wind Mass-Loading in the Born-Again Planetary Nebula A 30
Authors: Guerrero Martín A. , Chu You-Hua , Hamann Wolf-Rainer , Oskinova Lidia , Schönberner Detlef , Todt Helge , Steffen Matthias , Ruiz Nieves , Gruendl Robert A. , Blair William P.
Published: August 2012

We present XMM-Newton and Chandra observations of the born-again planetary nebula A 30. These X-ray observations reveal a bright unresolved source at the position of the central star whose X-ray luminosity exceeds by far the model expectations for photospheric emission and for shocks within the stellar wind. We suggest that a “born-again hot bubble” may be responsible for this X-ray emission. Diffuse X-ray emission associated with the petal-like features and one of the H-poor knots seen in the optical is also found. The weakened emission of carbon lines in the spectrum of the diffuse emission can be interpreted as the dilution of stellar wind by mass-loading or as the detection of material ejected during a very late thermal pulse.
X-ray spectra of wind-driven bubbles with chemical gradients
Authors: Jacob Ralf , Sandin Christer , Schönberner Detlef , Steffen Matthias
Published: August 2012

As a tool helping to interpret diffuse X-ray emission of PNe, and as a supplement to our RHD simulations, we have started to construct a grid of theoretical X-ray spectra of wind-blown bubbles with temperature and density profiles according to thermal conduction theory. We investigate how the X-ray spectra depend on chemical composition (e.g. H-rich vs. H-deficient) and how temperature and abundance determinations reflect gradients of temperature and chemical composition within the bubbles. These synthetic models shall allow to quickly perform detailed parameter studies without the need for dedicated hydrodynamical simulations. We report on ideas and goals.
The influence of binarity on the morpho-kinematics of planetary nebulae
Authors: Jones David , Tyndall Amy A. , Lloyd Myfanwy , Santander-García Miguel
Published: August 2012

The role of central star binarity in the shaping of planetary nebulae (PNe) has been the subject of much debate, with single stars believed to be incapable of producing the most highly collimated morphologies. However, observational support for binary-induced shaping has been sadly lacking. Here, we highlight the results of a continuing programme to spatio-kinematically model the morphologies of all PNe known to contain a close binary central star. Spatio-kinematical modelling is imperative for these objects, as it circumvents the degeneracy between morphology and orientation which can adversely affect determinations of morphology based on imaging alone. Furthermore, spatio-kinematical modelling accurately determines the orientation of the nebular shell, allowing the theoretically predicted perpendicular alignment, between nebular symmetry axis and binary orbital plane, to be tested. To date, every PN subjected to this investigation has displayed the predicted alignment, indicating that binarity has played an important role in the formation and evolution of these nebulae. The further results from this programme will be key, not only in determining whether binary interaction is responsible for shaping the studied PNe, but also in assessing the importance of binarity in the formation and evolution of all PNe in general.
Grids of synthetic spectra for H-poor central stars of planetary nebulae (CSPNe)
Authors: Keller Graziela R. , Bianchi Luciana , Herald James E. , Maciel Walter J.
Published: August 2012

We present comprehensive grids of model spectra from far-UV to IR, covering the parameter space of [WC] (Keller et al. 2011) and PG1159 stars. Models are calculated with the CMFGEN code, accounting for non-LTE, line blanketing, wind, clumping, and including ions previously neglected. The grids are available at http://dolomiti.pha.jhu.edu/planetarynebulae.html. We used them to analyse UV and far-UV spectra of NGC6905's and NGC5189's central stars.
The growth of the outflows from evolved stars: A live poster
Authors: Liimets Tiina , Corradi Romano L. M. , Balick Bruce , Santander-García Miguel
Published: August 2012

We present our long-term monitoring, using both ground-based telescopes and the HST, of the expansion in the plane of the sky of the outflows from evolved stars. They include the PN M2–9 (suspected of hosting a symbiotic nucleus), the classical nova remnant GK Per, the symbiotic Miras R Aqr, Hen 2–147 and Hen 2–104, and the proto-PNe CRL 618, CRL 2688, and Hen 3–1475.
Radial abundance gradients from planetary nebulae and young objects: Age effects
Authors: Maciel Walter J. , Rodrigues Thaise , Costa Roberto
Published: August 2012

We discuss the effects on the time variation of the gradients resulting from our determinations of the age distributions of CSPN. The main conclusions are: (i) for most CSPN with accurate radial velocities the kinematic ages are usually under 3 Gyr, so that the differences between the gradients of these objects and of younger objects are expected to be small; (ii) results based on age-metallicity relations suggest that there is an older PN population for which the gradients are steeper, in agreement with open cluster data.
Spectral analysis of PG 1034+001, the exciting star of Hewett 1
Authors: Mahsereci Marin , Ringat Ellen , Rauch Thomas , Werner Klaus , Kruk Jeffrey W.
Published: August 2012

PG 1034+001 is an extremely hot, helium-rich DO-type star that excites the planetary nebula Hewett 1 and large parts of the surrounding interstellar medium. We present preliminary results of an ongoing spectral analysis by means of non-LTE model atmospheres that consider most elements from hydrogen to nickel. This analysis is based on high-resolution ultraviolet (FUSE, IUE) and optical (VLT/UVES, Keck) data. The results are compared with those of PG 1034+001's spectroscopic twin, the DO star PG 0038+199.
Gaia future contribution to the study of PNe
Authors: Manteiga Minia , Arcay Bernardino , Ulla Ana , Aller Alba , Miranda Luis. F. , Isasi Yago ,   Gaia DPAC
Published: August 2012

Gaia, the forthcoming astrometric ESA survey, is expected to substantially improve our knowledge about the distances to galactic planetary nebulae (PNe). We present an overview of Gaia mission and focus in some aspects which are relevant for the study of PNe. In particular, we present our simulations on Gaia spectrophotometric observations obtained by means of GOG (Gaia Object Generator) for a catalogue of proto-PNe and PNe (Suárez et al. 2006) which can be used as templates to classify and study the suitability of Gaia spectrophotometry to infer physical properties of the sources.
Luminosity and abundance correlations in a carefully-studied sample of PNe
Authors: McKeever Jean , Balick Bruce , Lutz Julie , Braxton Kelsey , Gomez Thomas , Kwitter Karen , Henry Richard C.B.
Published: August 2012

We have searched for correlated trends in He/H, N/H, O/H, Ne/H, Ar/H, Cl/H, and S/H abundances with their luminosities, Peimbert types, galactocentric radius, emission-line luminosities, diameters, morphologies, surface brightnesses among Galactic planetary nebulae (PNe) using a database of 119 PNe with well measured properties. We report selected highlights.
Peculiar CNO photospheric abundances in the central star of NGC 2392
Authors: Méndez Roberto H. , Urbaneja Miguel A. , Kudritzki Rolf-Peter , Prinja Raman K.
Published: August 2012

Using new, high signal-to-noise CFHT ESPaDOnS visual spectrograms, and archive IUE and FUSE UV spectrograms, together with state-of-the-art non-LTE hydrodynamical model atmospheres, we have obtained accurate He, C, N, O photospheric abundance determinations in the central stars of NGC 2392, IC 4593, and NGC 6826. We compare with the corresponding nebular abundances, taken from the literature. The central star of NGC 2392 shows high He, N, and very low C, O abundances. We propose that these peculiar abundances must have originated in a common-envelope phase of interaction with a close binary companion. If we assume that the companion is more evolved than the visible central star, this offers a way of solving the old mystery of the discrepant He II Zanstra temperature of NGC 2392.
Planetary nebulae in the VISTA Magellanic Cloud (VMC) Survey
Authors: Miszalski Brent , Napiwotzki Ralph , Cioni Maria-Rosa L. , Groenewegen Martin A. T. , Oliveira Jose M. , Udalski Andrzej , Nie Jia-Cai
Published: August 2012

The multi-epoch YJKs sub-arcsecond photometry of the VMC survey provides a long anticipated deep near-infrared (NIR) window into further understanding the stellar populations of the Magellanic Clouds. The first year of observations consisted of six tiles covering ~9% of the Large Magellanic Cloud (LMC) survey region and contains 102 objects previously classified as planetary nebulae (PNe). A large proportion of the sample were found to be contaminated by non-PNe. These initial results underline the importance of establishing a clean catalogue of LMC PNe before they are applied in areas such as the planetary nebula luminosity function (PNLF) and searches for binary central stars. As the VMC survey progresses it will play a fundamental role in cleaning extant PN catalogues and a complementary role in the discovery of new PNe.
Early results from ChanPLaNS: Mystery of hard X-ray emitting CSPNe
Authors: Montez Rodolfo , Kastner J. H. , Balick B. , Behar E. , Blackman E. , Bujarrabal V. , Chu Y.-H. , Corradi R. , De Marco O. , Frank A. , Frew D. , Guerrero M. , Kwok S. , Lopez J. A. , Miszalski B. , Nordhaus J. , Parker Q. , Sahai R. , Sandin C. , Schoenberner D. , Soker N. , Sokoloski J. , Steffen W. , Ueta T. , Villaver E. , Zijlstra A.
Published: August 2012

We are presently using the Chandra X-ray Observatory to conduct the first systematic X-ray survey of planetary nebulae (PNe) in the solar neighborhood. The Chandra Planetary Nebula Survey (ChanPlaNS) is a 570 ks Chandra Cycle 12 Large Program targeting 21 high-excitation PNe within ~1.5 kpc of Earth. When complete, this survey will provide a suite of new X-ray diagnostics that will inform the study of late stellar evolution, binary star astrophysics, and wind interactions. Among the early results of ChanPlaNS (when combined with archival Chandra data) is a surprisingly high detection rate of relatively hard X-ray emission from CSPNe. Specifically, X-ray point sources are clearly detected in roughly half of the ~30 high-excitation PNe observed thus far by Chandra, and all but one of these X-ray-emitting CSPNe display evidence for a hard (few MK) component in their Chandra spectra. Only the central star of the Dumbbell appears to display “pure” hot blackbody emission from a ~200 kK hot white dwarf photosphere in the X-ray band. Potential explanations for the“excess” hard X-ray emission detected from the other CSPNe include late-type companions (heretofore undetected, in most cases) whose coronae have been rejuvenated by recent interactions with the mass-losing WD progenitor, non-LTE effects in hot white dwarf photospheres, self-shocking variable winds from the central star, and slow (re-)accretion of previously ejected red giant envelope mass.
∊ Aur in eclipse: Post-AGB primary and disk-shaped secondary
Authors: Muthumariappan Chinnathambi , Parthasarathy Mudumba , Jayakumar Kanniah , Appakutty Manickam
Published: August 2012

We present physical and chemcal properties of the disk in the eclipsing binary system ∊ Aur by solving 2D radiative transfer problem. We also present preliminary results of our high resolution spectroscopic monitoring of K I, Na, and Hα line profiles variation during the totality phase of the recent eclipse of ∊ Aur.
Processing of polycyclic aromatic hydrocarbons in evolved planetary nebulae
Authors: Ohsawa Ryou , Onaka Takashi , Sakon Itsuki , Yamamura Issei , Matsuura Mikako , Kaneda Hidehiro
Published: August 2012

We investigate the infrared emission bands from Polycyclic Aromatic Hydrocarbons (PAHs) in Galactic planetary nebulae (PNe). PAHs in PNe are assumed to be in transition from circumstellar to interstellar PAHs. We select 15 evolved PNe taking account of effective stellar temperatures and obtain infrared spectra of PNe from AKARI (2.5–5 μm) and Spitzer (5–14 μm) observations. Their evolutionary phase is estimated using [SIV]10.51/[NeII]12.81. We find that the near-infrared PAH bands are significantly enhanced along with stellar evolution sequence. We also find that the ratio of 3.4 to 3.3 μm bands is enhanced. The enhancement might indicate some chemical processing, such as hydrogenation, on small PAHs.
Low dispersion spectroscopy of point-symmetric planetary nebulae
Authors: Olguín Lorenzo , Vázquez Roberto , Contreras María E. , Sabin Laurence , Guillén Pedro F.
Published: August 2012

We present an observational study of three oint-ymmetric lanetary ebulae (PS-PNe): PC 19, He 2-429, and He 1-1, whose kinematics has been previously reported in the literature. The study includes an analysis of physical conditions and chemical abundances. We found that the abundances of He 2-429 and He 1-1 correspond to a Peimbert Type I PNe while those of PC 19 are in good agreement with a Type IV PN. Kinematic evidence derived from proper motion measurement support PC 19 classification and suggest that the progenitor star was a low-mass low-metallicity member of the galactic halo population.
He I temperatures in planetary nebulae
Authors: Peimbert Antonio , Peimbert Manuel
Published: August 2012

It is well established that PNe are not thermally homogeneous, beyond what chemically homogeneous photoionization models predict. To discriminate between the different scenarios proposed in the literature, we have determined the temperature based on He I lines for a dozen PNe. We compare these determinations with those derived from the Balmer continua. We find that the He I temperatures agree with the Balmer temperatures and that both are lower than those derived from CELs; suggesting that most PNe are chemically homogeneous.
Filling factor and temperature variations in planetary nebulae
Authors: Peimbert Manuel , Peimbert Antonio
Published: August 2012

We have found a strong correlation between small filling factors and large t2 values in planetary nebulae. We have also found that in general the filling factor for Type I PNe is smaller than for Type II PNe. These results imply that the abundance correction due to temperature inhomogeneities in general is larger for Type I PNe than for Type II PNe. This difference permits to reproduce the expected abundance difference between PNe of Type I and II predicted by Galactic chemical evolution models.
H2O maser polarization of the water fountains IRAS 15445–5449 and IRAS 18043–2116
Authors: Pérez-Sánchez Andrés F. , Vlemmings Wouter H. T. , Chapman Jessica M.
Published: August 2012

We present the morphology and linear polarization of the 22-GHz H2O masers in the high-velocity outflow of two post-AGB sources, d46 (IRAS 15445–5449) and b292 (IRAS 18043–2116). The observations were performed using The Australia Telescope Compact Array. Different levels of saturated maser emission have been detected for both sources. We also present the mid-infrared image of d46 overlaid with the distribution of the maser features that we have observed in the red-shifted lobe of the bipolar structure. The relative position of the observed masers and a previous radio continuum observation suggests that the continnum is produced along the blue-shifted lobe of the jet. It is likely due to synchrontron radiation, implying the presence of a strong magnetic field in the jet. The fractional polarization levels measured for the maser features of d46 indicate that the polarization vectors are tracing the poloidal component of the magnetic field in the emitting region. For the H2O masers of b292 we have measured low levels of fractional linear polarization. The linear polarization in the H2O maser region of this source likely indicates a dominant toroidal or poloidal magnetic field component.
Nebula around R Corona Borealis
Authors: Rao N. Kameswara , Lambert David L.
Published: August 2012

The star R Corona Borealis (R CrB) shows forbidden lines of [O II], [N II], and [S II] during the deep minimum when the star is fainter by about 8 to 9 magnitudes from normal brightness, suggesting the presence of nebular material around it. We present low and high spectral resolution observations of these lines during the ongoing deep minimum of R CrB, which started in July 2007. These emission lines show double peaks with a separation of about 170 km/s. The line ratios of [S II] and [O II] suggest an electron density of about 100 cm−3. We discuss the physical conditions and possible origins of this low density gas. These forbidden lines have also been seen in other R Coronae Borealis stars during their deep light minima and this is a general characteristic of these stars, which might have some relevance to their origins.
Spectral analysis of the O(He)-type central stars of the planetary nebulae K 1-27 and LoTr 4
Authors: Reindl Nicole , Ringat Ellen , Rauch Thomas , Werner Klaus , Kruk Jeffrey. W.
Published: August 2012

The four known O(He) stars are the only amongst the hottest post-AGB stars whose atmospheres are composed of almost pure helium. Thus, their evolution deviates from the hydrogen-deficient post-AGB evolutionary sequence of carbon-dominated stars like e.g. PG 1159 stars. The origin of the O(He) stars is still not explained. They might be either post-early AGB stars or the progeny of R Coronae Borealis stars. We present preliminary results of a non-LTE spectral analysis based on FUSE and HST/COS observations.
The multi-polar planetary nebula NGC 5189
Authors: Sabin Laurence , Vázquez Roberto , Lopéz Jose A. , García-Diaz Maria-Teresa
Published: August 2012

NGC 5189 is a particularly interesting planetary nebula (PN) displaying multiple bipolar structures. This type of morphology is generally attributed to multiple mass loss events believed to originate from a precessing central source. In order to better understand this, once dubbed chaotic PN, we have investigated optical imaging combined with low- and high- resolution spectroscopic data to dissect its components. The imaging reveals three and possibly four well defined bipolar lobes showing a misalignment with respect to the central torus, although sharing the same geometric center. The high nitrogen levels detected in the elongated filaments/condensations surrounding the nebula and at the torus location highlight the presence of low ionization structures as well as the possible occurrence of shocks in the areas perturbed by large dynamical motions. Finally the kinematical study indicates moderate expansion velocities (35 km.s−1 in the western lobe, 33 km.s−1 in the central region and 44 km.s−1 in the eastern lobe). We also notice the asymmetry of the [NII] distribution and the velocities inside NGC 5189 between its North-West and South-East components.
New planetary nebulae with ISM interaction discovered with IPHAS
Authors: Sabin Laurence , Corradi Romano L. M. , Parker Quentin , Mampaso Antonio , Zijlstra Albert
Published: August 2012

The low surface brightness usually associated with nebulae mixing with the ISM has long been a substantial obstacle in the observation and statistical study of these interactions. Thanks to the detection capability of the INT Photometric H-alpha Survey (IPHAS), in terms of sensitivity and imaging resolution, we were able to detect and select tens of examples of candidate Planetary Nebulae apparently at different stages of interaction with the interstellar medium (PNe-ISM hereafter) following the Wareing et al. (2007) classification. A spectroscopic investigation was conducted with the San Pedro Martir 2.1m telescope (SPM) in Mexico and we present the first results involving a proper classification and analysis of our candidates. The main difficulty is visually separating PNe-ISM from other faint asymmetric nebulosities such as old HII regions, SNRs and general diffuse H-alpha structures. This investigation is a first step in a more comprehensive study of PNe-ISM as more candidates are uncovered by the IPHAS team.
The role of heat conduction to the formation of [WC]-type planetary nebulae
Authors: Sandin Christer , Steffen Matthias , Jacob Ralf , Schönberner Detlef , Rühling Ute , Hamann Wolf-Rainer , Todt Helge
Published: August 2012

X-ray observations of young Planetary Nebulæ (PNe) have revealed diffuse emission in extended regions around both H-rich and H-deficient central stars. In order to also reproduce physical properties of H-deficient objects, we have, at first, extended our time-dependent radiation-hydrodynamic models with heat conduction for such conditions. Here we present some of the important physical concepts, which determine how and when a hot wind-blown bubble forms. In this study we have had to consider the, largely unknown, evolution of the CSPN, the slow (AGB) wind, the fast hot-CSPN wind, and the chemical composition. The main conclusion of our work is that heat conduction is needed to explain X-ray properties of wind-blown bubbles also in H-deficient objects.
Studies of planetary nebulae with SOFIA: Current and future prospects
Authors: Sankrit Ravi
Published: August 2012

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is introduced, its basic properties are presented, and the relevance of the observatory to Planetary Nebula studies is described.
A detailed look at chemical abundances in the Magellanic Clouds
Authors: Shaw Richard A. , Lee Ting-Hui , Stanghellini Letizia , Davies James E. , García-Hernández D. Anibal , García-Lario Pedro , Perea-Calderón Jose-Vicente , Villaver Eva , Manchado Arturo , Palen Stacy , Balick Bruce
Published: August 2012

We determine elemental abundances of He, N, O, Ne, S, and Ar in Magellanic Cloud planetary nebulae (PNe) using direct methods and a large set of observed ions, minimizing the need for ionization correction factors. In contrast to prior studies, we find a clear separation between Type I and non-Type I PNe in these low-metallicity environments, and no evidence that the O-N nucleosynthesis cycle is active in low-mass progenitors. We find that the S/O abundance ratio is anomalously low compared to H ii regions, confirming the “sulfur anomaly” found for Galactic PNe. We also found that Ne/O is elevated in some cases, raising the possibility that Ne yields in low-mass AGB stars may be enhanced at low metallicity.
Radiative transfer model of the dust structures of CRL 2688
Authors: Vinković Dejan , Balick Bruce
Published: August 2012

New Hubble images of the reflection nebula CRL 2688 from 0.6 to 1.6μm reveal significant variations of color and opacity in the distribution of scattered starlight. We have constructed a detailed radiation-transfer model consisting principally of an optically thick equatorial disk-like structure; bipolar lobes with density enhancements along the polar axis and at the base of lobes; an optically thin extended envelope containing spherical density-enhanced shells to mimic the outer rings of CRL 2688; and a pair of near-stellar caps that collimate and redden the dispersing starlight near its source. Our model nicely reproduces all of the basic features detected in the HST images, including the famous searchlights and arcs, as well as the measured spectral energy distribution (“SED”) of CRL 2688. Assuming a distance of 420 pc we estimate the light originates in a giant star with a temperature T ~ 7000 K and a luminosity L = 5500 ± 1100 L⊙.
Towards a Legal Framework for Coastal Adaptation: Assessing the First Steps in Europe and Australia
Authors: Verschuuren Jonathan , McDonald Jan
Published: August 2012

In light of the urgent need for coastal adaptation policies and the impediments to their implementation, this article examines the early experience with coastal adaptation policies in the EU (in particular the Netherlands and the UK) and Australia, with a view to identifying the important features of an effective regulatory framework for coastal adaptation. We conclude that an integrated approach to coastal adaptation law is currently needed to lay the foundations for the required long-term strategy. Such an approach would establish processes by which adaptation objectives are agreed for each part of the coast, ensure land use planning that can accommodate future change and does not expose new communities to risk, integrate coastal adaptation with biodiversity and coastal zone policy, allocate regulatory responsibility in a way that promotes subsidiarity and consistency, and ensure that funds are available for future measures.