Modeling the dust emission from PN IC418

We construct a detailed model for the IR dust emission from the PN IC 418. We succeed to reproduce the emission from 2 to 200$\mu$m. We can determine the amount of emitting dust as well as its composition, and compare to the depletion of elements determined for the photoionized region.Comment: Poster contribution (2 pages, 1 figure) to IAU Symposium 283: "Planetary Nebulae: An Eye to the Future" held in Puerto de la Cruz, Tenerife, Spain in July 25th-29th 2011. Few typos correcte

La programación de la producción en el sector del automóvil. El problema de la segmentación.

La Gestión de la Cadena de Suministro en el sector del automóvil, así como las relaciones entre ensamblador y proveedores de primera línea han adquirido una gran importancia en los últimos años. Se constata la importancia que los procesos de negocio de s

The second release of the Toru\'n catalogue of Galactic post-AGB objects: new classification scheme

The investigation of post-AGB objects (proto-planetary nebulae) is very important from the standpoint of physical and chemical changes occurring during the late stages of stellar evolution. The Toru\'n catalogue of Galactic post-AGB and related objects is an evolutive catalogue containing astrometric, photometric and spectroscopic data as well as HST images for all known post-AGB objects and candidates in our Galaxy. This free-access catalogue can serve as an ideal tool to study different groups of post-AGB objects, especially due to the fact that all information is gathered in one place. The second release of our catalogue introduces a simple classification scheme of post-AGB objects and includes a significant number of new objects, photometric data, spectra and images. Here, using objects from the catalogue we consider the problem of the termination of the AGB phase.Comment: 1 figure, poster during IAUS 283, Planetary Nebulae: an Eye to the Futur

A Detailed Look at Chemical Abundances in Magellanic Cloud Planetary Nebulae. I. The Small Magellanic Cloud

We present an analysis of elemental abundances of He, N, O, Ne, S, and Ar in Magellanic Cloud planetary nebulae (PNe), and focus initially on 14 PNe in the Small Magellanic Cloud (SMC). We derived the abundances from a combination of deep, high dispersion optical spectra, as well as mid-infrared (IR) spectra from the Spitzer Space Telescope. A detailed comparison with prior SMC PN studies shows that significant variations among authors of relative emission line flux determinations lead to systematic discrepancies in derived elemental abundances between studies that are >~0.15 dex, in spite of similar analysis methods. We used ionic abundances derived from IR emission lines, including those from ionization stages not observable in the optical, to examine the accuracy of some commonly used recipes for ionization correction factors (ICFs). These ICFs, which were developed for ions observed in the optical and ultraviolet, relate ionic abundances to total elemental abundances. We find that most of these ICFs work very well even in the limit of substantially sub-Solar metallicities, except for PNe with very high ionization. Our abundance analysis shows enhancements of He and N that are predicted from prior dredge-up processes of the progenitors on the AGB, as well as the well known correlations among O, Ne, S, and Ar that are little affected by nucleosynthesis in this mass range. We identified MG_8 as an interesting limiting case of a PN central star with a ~3.5 M_sun progenitor in which hot-bottom burning did not occur in its prior AGB evolution. We find no evidence for O depletion in the progenitor AGB stars via the O-N cycle, which is consistent with predictions for lower-mass stars. We also find low S/O ratios relative to SMC H_II regions, with a deficit comparable to what has been found for Galactic PNe.Comment: 9 figures, 6 tables; to be published in Ap

The nature of dust in compact Galactic planetary nebulae from Spitzer spectra

We present the Spitzer/IRS spectra of 157 compact Galactic PNe. These young PNe provide insight on the effects of dust in early post-AGB evolution, before much of the dust is altered or destroyed by the hardening stellar radiation field. Most of the selected targets have PN-type IRS spectra, while a few turned out to be misclassified stars. We inspected the group properties of the PN spectra and classified them based on the different dust classes (featureless, carbon-rich dust; oxygen-rich dust; mixed-chemistry dust) and subclasses (aromatic and aliphatic; crystalline and amorphous). All PNe are characterized by dust continuum and more than 80% of the sample shows solid state features above the continuum, in contrast with the Magellanic Cloud sample where only ~40% of the entire sample displays solid state features; this is an indication of the strong link between dust properties and metallicity. The Galactic PNe that show solid state features are almost equally divided among the CRD, ORD, and MCD. We analyzed dust properties together with other PN properties and found that (i) there is an enhancement of MCD PNe toward the Galactic center; (ii) CRD PNe could be seen as defining an evolutionary sequence, contrary to the ORD and MCD PNe; (iii) C- and O-rich grains retain different equilibrium temperatures, as expected from models; (iv) ORD PNe are highly asymmetric and CRD PNe highly symmetric; point-symmetry is statistically more common in MCD. We find that the Galactic Disk sample does not include MCD PNe, and the other dust classes are differently populated from high to low metallicity environments. The MCPNe seem to attain higher dust temperatures at similar evolutionary stages, in agreement with the observational findings of smaller dust grains in low metallicity interstellar environments.Comment: The Astrophysical Journal, in press (76 pages, 36 figures and 6 Tables

Birth and early evolution of a planetary nebula

The final expulsion of gas by a star as it forms a planetary nebula --- the ionized shell of gas often observed surrounding a young white dwarf --- is one of the most poorly understood stages of stellar evolution. Such nebulae form extremely rapidly (about 100 years for the ionization) and so the formation process is inherently difficult to observe. Particularly puzzling is how a spherical star can produce a highly asymmetric nebula with collimated outflows. Here we report optical observations of the Stingray Nebula which has become an ionized planetary nebula within the past few decades. We find that the collimated outflows are already evident, and we have identified the nebular structure that focuses the outflows. We have also found a companion star, reinforcing previous suspicions that binary companions play an important role in shaping planetary nebulae and changing the direction of successive outflows.Comment: 9 pages + 3 figures. To appear in Nature, 2 April 199

Estructuras de licuefacción sísmica en el yacimiento romano de La Magdalena, Complutum s. IV AD (Madrid, España)

la antigua ciudad romana de Complutum (Alcalá de Henares, Madrid) fue fundada en el s. I AD y fue una de las ciudades más importantes de Hispania. Complutum fue destruida, abandonada bruscamente, reubicada y reconstruida en una nueva localización en el s. IV AD. Las causas de la destrucción y la nueva localización de la ciudad son aún una incógnita para la arqueología. En este trabajo se muestran diferentes efectos arqueosismológicos de terremotos (EAEs) afectando al yacimiento de La Magdalena (una explotación agrícola situada a 4 km al NE del núcleo urbano de Complutum). El efecto geológico de origen sísmico que afectó al yacimiento es la licuefacción. Se pueden observar diques de arena y cráteres de gravas por explosión afectando a instalaciones romanas, como cisternas, casas o tumbas. Simultáneamente al abandono de La Magdalena también fueron abandonadas de forma brusca la ciudad de Complutum y varias villas romanas a lo largo del valle del Henares, en algunos casos con EAEs que pueden asociarse al mismo evento que destruyó el yacimiento de La Magdalena. Estos EAEs podrían estar generados por un terremoto de Mw = 5.0-6,6, utilizando los límites empíricos de licuefacción y ruptura cosísmica de la fallaInstituto Geológico y Minero de España, EspañaDepartamento de Geología, Escuela Politécnica Superior de Ávila, Universidad Salamanca, EspañaTrébede, Patrimonio Cultural, S.L., EspañaUniversidad de Salamanca, EspañaFacultad de Ciencias, Universidad Autónoma de Madrid, EspañaDepartamento de Ingeniería del Terreno, Escuela Politécnica Superior de Ávila, Universidad de Salamanca, EspañaDepartamento de Edafología, Escuela Técnica Superior de Ingenieros Agrónomos, Universidad Politécnica de Madrid, EspañaFacultad de Ciencias, Universidad Nacional de Educación a Distancia, EspañaDepartamento de Geología, Universidad de Alcalá de Henares, Españ