bluuebunny/crossref_metadata_2025_split huggingface dataset:
Are planetary nebulae derived from multiple evolutionary scenarios?
Authors: Frew David J. , Parker Quentin A. 
Published: August 2012

AbstractOur understanding of planetary nebulae has been significantly enhanced as a result of several recent large surveys (Parkeret al., these proceedings). These new discoveries suggest that the ‘PN phenomenon’ is in fact more heterogeneous than previously envisaged. Even after the careful elimination of mimics from Galactic PN catalogues, there remains a surprising diversity in the population of PNe and especially their central stars. Indeed, several evolutionary scenarios are implicated in the formation of objects presently catalogued as PNe. We provide a summary of these evolutionary pathways and give examples of each. Eventually, a full census of local PNe can be used to confront both stellar evolution theory and population synthesis models.
X-ray observations of central stars of planetary nebulae and their winds
Authors: Guerrero Martín A. 
Published: August 2012

AbstractThe photospheric emission from the hottest central stars of planetary nebulae (CSPNe) is capable to extend into the X-ray domain, with emission peaking at 0.1-0.2 keV and vanishing above 0.4 keV. Unexpected, intriguing hard X-ray emission with energies greater than 0.5 keV has been reported for several CSPNe and for a number of white dwarfs (WDs). Different mechanisms may be responsible for the hard X-ray emission from CSPNe and WDs: coronal emission from a late-type companion, shocks in fast winds as in OB stars, leakage from underneath the star photosphere, or accretion of material from a disk, a companion star, or the circumstellar medium. Therefore, the hard X-ray emission associated with CSPNe may have significant implications for our understanding of the formation of PNe: binary companions, disks, and magnetic fields are thought to play a major role in the shaping of PNe, whereas clumping in the stellar wind may have notable effects in the PN evolution by modifying the stellar mechanical energy output. Here I present the results of different observational efforts to search for hard X-ray emission from CSPNe and discuss the different mechanisms for the production of hard X-rays.
Post-AGB stars in the LMC and SMC
Authors: Van Winckel Hans , van Aarle Els , Wood Peter R. , Kamath Devika , Evans Tom Lloyd , De Smedt Kenneth , Gorlova Nadya , Gielen Clio 
Published: August 2012

AbstractGalactic post-AGB stars show a large diversity in chemical compositions as well as in the kinematical and geometrical properties of their circumstellar material. The theoretical interpretation is hampered by the lack of good distances to almost all Galactic objects. We therefore initiated a large project to study systematically post-AGB stars in the Large and Small Magellanic Cloud (LMC, SMC respectively). Here we report on our preliminary results.
M31 Planetary nebulae as seen by the Panchromatic Hubble Andromeda Treasury
Authors: Rosenfield Philip A. , Johnson L. Clifton , Girardi Léo , Dalcanton Julianne J. , Williams Benjamin F. , Bianchi Luciana , Marigo Paola , Caldwell Nelson , Seth Anil C. , Gordon Karl , Lan Dustin 
Published: August 2012

AbstractWe present a preliminary analysis of known planetary nebulae (PNe) in M31 that were observed in the first year of the Panchromatic Hubble Andromeda Treasury HST Multi-cycle program. We use the properties of this sample to discuss PNe from this new multi-band survey.
The central planetary nebulae populations of external galaxies with SAURON
Authors: Sarzi Marc 
Published: August 2012

AbstractThanks to SAURON integral-field observations we uncovered the planetary nebulae (PNe) populations inhabiting the central and nuclear regions of our galactic neighbours M32 and M31, respectively, and discuss the significant differences between their corresponding PNe luminosity functions in light of the properties of their parent stellar populations. In particular, we conclude that the lack of bright PNe in the nuclear regions of M31 is likely linked to the nearly Solar value for the stellar metallicity, consistent with previous suggestions that a larger metallicity would bias the horizontal-branch (HB) populations toward bluer colors, leading to fewer red HB stars capable of producing PNe and more blue HB stars that instead could contribute to the far-UV flux observed in metal-rich early-type galaxies and, incidentally, in the nucleus of M31.
Combined modelling of the He2-131 planetary nebula and of its central star
Authors: Arrieta Anabel , Morisset Christophe , Hillier D. John , Stasińska Grażyna , Georgiev Leonid N. 
Published: August 2012

AbstractWe present a unified model of the central star and the ionized gas of the planetary nebula He2-131. Preliminary values of the nebular and stellar parameters are given together with those of the chemical composition.
Spectral analysis of mid-IR excesses of central stars of planetary nebulae
Authors: Bilikova Jana , Chu You-Hua , Su Kate Y.L. , Gruendl Robert 
Published: August 2012

AbstractIn our Spitzer 24 μm survey of hot white dwarfs (WDs) we found 9 WDs with IR excesses, 7 of them are still central stars of planetary nebulae (CSPNs). We have thus carried out a Spitzer archival survey of CSPNs, and found additional objects with IR excesses. To date, a total of 13 CSPNs show IR excesses from Spitzer observations. These mid-IR excesses are indicative of the presence of circumstellar dust, which could be produced by collisions or disruption of sub-planetary objects. To further assess the nature of these IR excesses, we have obtained Spitzer IRS, Gemini NIRI and Michelle, and KPNO 4m echelle spectra of these objects. In this poster, we summarize the spectroscopic observations and discuss the nature of these IR excesses.
VISIR-VLT images of the water maser: Emitting planetary nebula K3-35
Authors: Blanco Mónica W. , Guerrero Martín A. , Miranda Luis F. , Lagadec Eric , Suárez Olga 
Published: August 2012

AbstractK3-35 is an extremely young bipolar planetary nebula that contains a precessing bipolar jet and a small (radius 80 AU) water maser equatorial ring. We have obtained VISIR-VLT images of K3-35 in the PAH1 (λ=8.6 μm), [S iv] (λ=10.6 μm), and SiC (λ=11.85 μm) filters to analize the mid-IR morphology and the temperature structure of its dust emission. The images show the innermost nebular regions undetected at optical wavelegths and the precessing bipolar jets. The temperature map shows variations in the temperature in the equatorial zone and in regions associated to its jets.
A barium-rich binary central star in Abell 70
Authors: Boffin Henri M. J. , Miszalski Brent , Frew David J. , Acker Agnes , Köppen Joachim , Moffat Anthony F. J. , Parker Quentin A. 
Published: August 2012

AbstractWe have found the central star of Abell 70 (PN G038.1–25.4, hereafter A 70) to be a binary consisting of a G8 IV-V secondary and a hot white dwarf. The secondary shows enhanced Ba II and Sr II features, firmly classifying it as a barium star. The nebula is found to have Type-I chemical abundances with helium and nitrogen enrichment, which combined with future abundance studies of the central star, will establish A 70 as a unique laboratory for studying s-process AGB nucleosynthesis.
Herschel/HIFI observations of molecular lines from young planetary nebulae
Authors: Bujarrabal Valentín , Santander-García Miguel , Alcolea Javier , Soria Rebeca ,   the HIFISTARS team
Published: August 2012

AbstractWe present results from systematic Herschel/HIFI observations of molecular lines in the FIR/sub-mm from young planetary nebulae. The high spectral resolution provided by the hetorodyne spectrometer HIFI allows properly studying the line profiles, whose structure corresponds to the various kinematics of the most massive nebular components, including fast bipolar outflows and slow shells. In particular, we have studied the excitation properties of the high-velocity (dense) flows. In some cases we find typical temperatures of the fast gas over 100-200 K, though in others it remains cool, ≲30K. We argue that the thermodynamics of the molecule-rich bipolar outflows is driven by fast radiative cooling, after the passage of the shock that accelerated it.
Could some meteoritic stardust have originated from the winds of post-AGB stars and planetary nebula nuclei?
Authors: Buntain Joelene , Lugaro Maria , Karakas Amanda 
Published: August 2012

AbstractAfter very dense and slow winds erode the outer layer of an asymptotic giant branch (AGB) star down to a thin H-rich layer (≃10−3 M⊙) the star becomes a post-AGB star and evolves at constant luminosity towards hotter temperatures. It may then becomes a planetary nebula nucleus (PNN) at the centre of a planetary nebula (PN). During these phases, the thin H-rich surface layer of the star is eroded by winds. Stardust oxide and silicate grains are recovered from meteorites. The origin of the “Group II grains” that show enrichments in 17O and depletions in 18O is currently explained by invoking the occurrence of some kind of extra-mixing process in AGB stars. We suggest instead that these grains originated from the winds of post-AGB stars and PNN. These winds show the signature of H-burning. We will do this by comparing our predictions from stellar models to the compositions observed in Group II stardust oxide and silicate grains. We find that the composition of the thin H-rich layer lost in the post-AGB and PNN winds is close to that of Group II grains, however the match with the Al ratios needs to be improved. Considering the uncertainities in the 25Mg and 26Al proton capture rates may be helped in this respect.
Molar extinction coefficient of fullerenes and related hydrogenated derivatives “fulleranes”
Authors: Cataldo Franco , Iglesias-Groth Susana , Manchado Arturo 
Published: August 2012

AbstractFullerenes, the carbon molecules with 60 and 70 atoms, were recently detected in a series of planetary nebulae, in protoplanetary nebulae and in other astrophysical objects. The detection and the quantitative determination of these molecules was made possible by the measurement of their reference infrared spectra and the relative molar extinction coefficients and integrated molar absorptivity on laboratory scale. It is expected that also fulleranes the hydrogenated derivatives of C60 and C70 may be present in the same objects where fullerenes were detected. This prompted us to synthesize the hydrogenated fullerenes, to record their infrared spectra and the measure the molar extinction coefficients and integrated molar absorptivity on laboratory scale to have a reference in the search of these fullerene derivatives in space
A detailed spatiokinematic model of the multipolar planetary nebula NGC 7026
Authors: Clark David M. , López Jose Alberto , Steffen Wolfgang , Richer Michael G. 
Published: August 2012

AbstractWe present the most extensive, long-slit, high-resolution coverage of the complex planetary nebula (PN), NGC 7026. Ten spectra were acquired using the Manchester Echelle Spectrometer at San Pedro Martir Observatory in Baja California, Mexico, and each shows exquisite detail, revealing the intricate structure of this object. Incorporating these spectra into the 3-dimensional visualization and kinematic program, Shape, and using HST images of NGC 7026, we have produced a detailed structural and kinematic model of this PN. Knowledge of the 3-D structure of this nebula is relevant to understand the physics behind the extended X-ray emission in this object.
Radio planetary nebulae in the Magellanic Clouds
Authors: Crawford Evan J. , Filipović Miroslav D. , Bojičić Ivan S. , Cohen Martin , Payne Jeff L. , De Horta Ain Y. , Reid Warren 
Published: August 2012

AbstractWe present preliminary results of our deep Australia Telescope Compact Array (ATCA) radio-continuum survey of the Magellanic Clouds Planetary Nebulae.
Physical parameters and chemical abundances in bipolar PNe
Authors: Costa Roberto D. D. , Faes Daniel M. , Morisset Christophe 
Published: August 2012

AbstractBipolar nebulae constitute a large subset of the planetary nebulae population. We present the first results of a project aimed to map physical parameters and chemical abundances across extended planetary nebulae with bipolar structure. These results can be used as input and constraints into numerical simulations in order to reproduce their properties in the visual band of the spectrum. This provides a way to examine the non-homogeneity present in this kind of object, as well as a tool to derive their intrinsic properties, like tridimensional geometry and matter distribution, central star properties, distance, and other properties in a self-consistent way. Here we show our results for two of these objects: IC 4406 and NGC 6572.
Estimating the binary fraction of planetary nebulae central stars
Authors: Douchin D. , De Marco O. , Frew D. J. , Jacoby G. H. , Passy J.-C. , Hillwig T. , Howell S. B. , Bond H. , Peyaud A. , Zijlstra A. , Napiwotzki R. , Jasniewicz G. , Parker Q. 
Published: August 2012

AbstractDuring the past 20 years, the idea that non-spherical planetary nebulae might need a binary or planetary interaction to be shaped was discussed by various authors. It is now generally agreed that the varied morphologies of planetary nebulae cannot be fully explained solely by single star evolution. Observationally, more binary central stars of planetary nebulae have been discovered, opening new possibilities to understand the connections between binarity and morphology. So far, ≃45 binary central stars of planetary nebulae have been detected, most being close systems detected via flux variability. In order to determine the PN binary fraction, one needs a method that can detect wider binaries. We present here recent results concentrating on binary infrared excess observations aimed at detecting binaries of any separation.
3D ionization structure and kinematics of NGC 2392
Authors: Dufour Reginald J. , Sick Jonathan N. , Hartigan Patrick M. , Henry Richard B. C. , Kwitter Karen B. , Bohigas Joaquin 
Published: August 2012

AbstractWe discuss the 3D morphology, ionization structure, and kinematics of NGC 2392, the “Eskimo,” based on new and archival HST imagery and new long-slit echelle spectroscopy. High spatial resolution ionization maps of the nebula were made from HST WFPC2 imagery and compared with their velocity structure in various emission lines from echelle spectra taken with the 4m telescope at Kitt Peak. The imagery and spectra were then compared to map the kinematics of the nebula in several emission lines and decode the 3-dimensional morphology and ionization structure of the nebula, including that of C+2 from C III] 1909 Å for the first time.
Herschel observations of NGC 7027
Authors: Exter Katrina M. , van Hoof Peter A.M , Van de Steene Griet C. , Ottensamer Roland , Wesson Roger , Barlow Mike J. , Ferland Gary J. , Porter Ryan L. ,   the MESS consortium
Published: August 2012

AbstractWe present our analysis of the spectra of NGC 7027 taken with the PACS and SPIRE instruments of the Herschel satellite.
Abundances and ADFs in planetary nebulae with [WC] central stars
Authors: García-Rojas Jorge , Peña Miriam , Morisset Cristophe , Ruiz Maria-Teresa 
Published: August 2012

AbstractWe present preliminary results obtained from the analysis of very deep echelle spectra of a dozen planetary nebulae with [WC] or weak emission lines (wels) central stars. The computed abundance discrepancy factors (ADFs) are moderate, with values lower than 4. In principle, no evidence of the H-poor metal enriched inclusions proposed by Liu et al. (2000) have been found. However, a detailed analysis of the data is in progress.
Planetary nebulae as tracers of the kinematic structure of the starburst galaxy IC 10
Authors: Gonçalves Denise R. , Teodorescu Ana M. , Alves-Brito Alan , Méndez Roberto H. , Magrini Laura 
Published: August 2012

AbstractThe Local Group dwarf irregular galaxy IC 10 is the nearest starburst galaxy (at 725 kpc) and presents extended and complex HI kinematics. It is believed that IC 10 is still experiencing an intense and very recent burst of star formation, likely triggered by infalling gas from an extended envelope which is counter-rotating with respect to the galaxy proper rotation. In this contribution we summarize our preliminary results (Gonçalves et al. 2011, in prep.) obtained by performing a kinematic analysis of the PN population of IC 10. Our aim is to explore the kinematic connection of its intermediate to old stellar populations with that obtained from HI observations. Some PNe were found at large galactocentric distances and could therefore represent a trace of past tidal interactions.
Deep spectroscopy of the dwarf spheroidal NGC 185
Authors: Gonçalves Denise R. , Magrini Laura , Martins Lucimara P. , Teodorescu Ana M. , Quireza Cintia , Lanfranchi Gaia 
Published: August 2012

AbstractDwarf galaxies are crucial to understand the formation and evolution of galaxies, since they constitute the most abundant galaxy population. Abundance ratios and their variations due to star formation and inflow/outflow of gas are key constraints to chemical evolution models. The determination of these abundances in the dwarf galaxies of the Local Universe is thus of extreme importance. NGC 185 is one of the four brightest dwarf companions of M31, but unlike the other three it has an important content of gas and dust. Interestingly enough, in an optical survey of bright nearby galaxies NGC 185 was classified as a Seyfert galaxy based on its integrated emission-line ratios in the nuclear regions. However, although its emission lines formally place it in the category of Seyfert it is probable that this galaxy does not contain a genuine active nucleus. In this contribution, we resume, firstly, our results of an empirical study of the galaxy, on which we characterise its emission-line population and obtain planetary nebulae abundance ratios (Gonçalves et al. 2012). And, secondly, we discuss our attempt to identify the possible ionization mechanisms for NGC 185 enlighting the controversial classification of this galaxy dwarf spheroidal (dSph) as well as Seyfert, via stellar population synthesis and chemical evolution modelling (Martins et al. 2011).
The curious conundrum regarding sulfur and oxygen abundances in planetary nebulae
Authors: Henry Richard B. C. , Speck Angela , Karakas Amanda I. , Ferland Gary J. 
Published: August 2012

AbstractWe carefully consider numerous explanations for the sulfur abundance anomaly in planetary nebulae. No one rationale appears to be satisfactory, and we suggest that the ultimate explanation is likely to be a heretofore unidentified feature of the nebular gas which significantly impacts the sulfur ionization correction factor.
Chemical evolution models for NGC 6822 using planetary nebulae abundances
Authors: Hernández-Martínez Liliana , Carigi Leticia , Peña Miriam , Peimbert Manuel 
Published: August 2012

AbstractWe present chemical evolution models for the dwarf irregular NGC 6822, using chemical abundances of Planetary Nebulae (PNe) and HII regions and also the mass of gas (Mgas) as observational constraints. Chemical evolution models have been calculated to reproduce the abundances as derived from both, collisionally excited lines (CELs) and recombination lines (RLs). In our models, the chemical contribution of low and intermediate mass stars (LIMS) is time delayed, while for the massive stars the chemical contribution is instantaneous, as in Franco & Carigi (2008). The chemical contribution of SNIa is included in our model, thus we are also able to reproduce the observational Fe/H abundance obtained from A stars.
On the production of multicharge ions in planetary nebulae
Authors: Ibadov Subhon 
Published: August 2012

AbstractProduction of multicharge ions due to generation of hot expanding plasma blobs, short-living “compound particles”, at high-velocity collisions between dust grains of a planetary nebula and dust particles of the interstellar medium is analytically considered. Dependence of the multiplicity of charge of produced ions on the relative velocity of colliding dust particles is determined.
Trigonometric parallax measurements of post-AGB stars with VERA
Authors: Imai Hiroshi , Tafoya Daniel ,   VERA collaboration
Published: August 2012

AbstractA trigonometric parallax distance is measurable for a planetary nebula if it harbors H2O (or OH) maser spots. We have demonstrated it for H2O maser sources, K3-35, IRAS 19312+1950 and IRAS 18286-0959 using the VLBI Exploration of Radio Astrometry (VERA). They are post-AGB stars and exhibit peculiar morpho-kinematical structures like a bipolar planetary nebula or a bipolar molecular jet (water fountain). The luminosities and secular motions of these sources derived from the trigonometric distances and proper motions of the H2O masers suggest that their parental stars may be intermediate-mass (2M⊙ < M* < 8 M⊙) evolved stars.
The nature of the Galactic bulge: A view from bulge planetary nebulae and globular clusters
Authors: Kholtygin Alexander F. , Milanova Yulia V. , Nikiforov Igor' I. , Vasyakina Olga V. 
Published: August 2012

AbstractModern data concerning the planetary nebulae (PNe) in the bulge, bar and disk of the Milky Way are used to study the chemical history of bulge. We show that the abundance pattern is similar for PNe in the bulge and Peimbert's type II PNe. We also found that the globular clusters (GCs), especially their metal-rich disk subsystem, form on metallicity maps a bar-like structure which parameters are very close to those for the Galactic bar. These results evidence an old age of the Galactic bulge and bar. We propose a scenario of the successive star formation in the bulge, bar and thin disk.
Investigation of the recombination of the retarded shell of “born-again” CSPNe by time-dependent radiative transfer models
Authors: Koskela Antti , Dalnodar Silvia , Kissmann Ralf , Reimer Anita , Ostermann Alexander , Kimeswenger Stefan 
Published: August 2012

AbstractA standard planetary nebula stays more than 10 000 years in the state of a photoionized nebula. As long as the timescales of the most important ionizing processes are much smaller, the ionization state can be characterized by a static photoionization model and simulated with codes like CLOUDY (Ferland et al. 1998). When the star exhibits a late helium flash, however, its ionizing flux stops within a very short period. The star then re-appears from its opaque shell after a few years (or centuries) as a cold giant star without any hard ionizing photons. Describing the physics of such behavior requires a fully time-dependent radiative transfer model. Pollacco (1999), Kerber et al. (1999) and Lechner & Kimeswenger (2004) used data of the old nebulae around V605 Aql and V4334 Sgr to derive a model of the pre-outburst state of the CSPN in a static model. Their argument was the long recombination time scale for such thin media. With regard to these models Schönberner (2008) critically raised the question whether a significant change in the ionization state (and thus the spectrum) has to be expected after a time of up to 80 years, and whether static models are applicable at all.
New faint planetary nebulae from the DSS and SDSS
Authors: Kronberger Matthias , Jacoby George H. , Ciardullo Robin , Crisp Richard D. , De Marco Orsola , Douchin Dimitri , Frew David J. , Harmer Dianne , Howell Mike , Howell Steve B. , Parker Quentin A. , Patchick Dana , Rector Travis , Riddle Dave , Teutsch Philipp 
Published: August 2012

AbstractHaving surveyed ≈ 10% of the sky, we have identified more than 130 PN candidates by surveying multicolour Digitized Sky Survey (DSS), Sloan Digitized Sky Survey (SDSS), and combined [O III], Hα and [S II] images. In a first imaging and spectroscopy campaign, 51 objects were identified as true and probable PNe. This work presents an additional 17 probable or possible PNe identified since that study. The majority of these candidates are situated at Galactic latitudes |b| > 5^, with the exception of seven objects located closer to the Galactic plane. Using the techniques described here that do not require any new survey data, we anticipate that many more PNe are waiting to be found, perhaps as many as 90.