229 research outputs found
Detection of a multi-shell planetary nebula around the hot subdwarf O-type star 2MASS J19310888+4324577
(Abridged) The origin of hot subdwarf O-type stars (sdOs) remains unclear
since their discovery in 1947. Among others, a post-Asymptotic Giant Branch
(post-AGB) origin is possible for a fraction of sdOs. We are involved in a
comprehensive ongoing study to search for and to analyze planetary nebulae
(PNe) around sdOs with the aim of establishing the fraction and properties of
sdOs with a post-AGB origin. We use deep Halpha and [OIII] images of sdOs to
detect nebular emission and intermediate resolution, long-slit optical
spectroscopy of the detected nebulae and their sdO central stars. These data
are complemented with other observations for further analysis of the detected
nebulae. We report the detection of an extremely faint, complex PN around 2MASS
J19310888+4324577 (2M1931+4324), a star classified as sdO in a binary system.
The PN shows a bipolar and an elliptical shell, whose major axes are oriented
perpendicular to each other, and high-excitation structures outside the two
shells. WISE archive images show faint, extended emission at 12 and 22 microns
in the inner nebular regions. The internal nebular kinematics is consistent
with a bipolar and a cylindrical/ellipsoidal shell, in both cases with the main
axis mainly perpendicular to the line of sight. The nebular spectrum only
exhibits Halpha, Hbeta and [OIII]4959,5007 emission lines, but suggests a very
low-excitation ([OIII]/Hbeta = 1.5), in strong contrast with the absence of
low-excitation emission lines. The spectrum of 2M1931+4324 presents narrow,
ionized helium absorptions that confirm the previous sdO classification and
suggest an effective temperature >= 60000 K. The binary nature of 2M1931+4324,
its association with a complex PN, and several properties of the system provide
strong support for the idea that binary central stars are a crucial ingredient
in the formation of complex PNe.Comment: 8 pages, 7 figures, accepted in Astronomy and Astrophysic
Hemi-Synthesis and Anti-Oomycete Activity of Analogues of Isocordoin
Indexación: Web of Science; Scopus.An efficient synthesis of a series of 4-oxyalkyl-isocordoin analogues (2–8) is reported for the first time. Their structures were confirmed by1H-NMR,13C-NMR, and HRMS. Their anti-oomycete activity was evaluated by mycelium and spores inhibition assay against two selected pathogenic oomycetes strains: Saprolegnia parasitica and Saprolegnia australis. The entire series of isocordoin derivatives (except compound 7) showed high inhibitory activity against these oomycete strains. Among them, compound 2 exhibited strong activity, with minimum inhibitory concentration (MIC) and minimum oomyceticidal concentration (MOC) values of 50 µg/mL and 75 µg/mL, respectively. The results showed that 4-oxyalkylated analogues of isocordoin could be potential anti-oomycete agents.http://www.mdpi.com/1420-3049/22/6/96
The origin of the planetary nebula M 1-16. A morphokinematic and chemical analysis
We investigated the origin of the Planetary Nebula (PN) M 1-16 using
narrow-band optical imaging, and high- and low-resolution optical spectra to
perform a detailed morpho-kinematic and chemical studies. M 1-16 is revealed to
be a multipolar PN that predominantly emits in [O III] in the inner part of the
nebula and [N II] in the lobes. A novel spectral unsharp masking technique was
applied to the position-velocity (PV) maps to reveal a set of multiple
structures at the centre of M 1-16 spanning radial velocities from
40kms to 20kms, with respect to the systemic velocity.
The morpho-kinematic model indicates that the deprojected velocity of the lobe
outflows are 100kms, and particularly the larger lobes and
knots have a deprojected velocity of 350kms; the inner
ellipsoidal component has a deprojected velocity of 29kms. A
kinematical age of 8700yr has been obtained from the model assuming a
homologous velocity expansion law and a distance of 6.21.9kpc. The
chemical analysis indicates that M 1-16 is a Type I PN with a central star of
PN (CSPN) mass in the range of 0.618-0.713M and an initial mass
for the progenitor star between 2.0 and 3.0M (depending on
metallicity). An 140000K and log=2.3
was estimated using the 3MdB photoionisation models to reproduce the ionisation
stage of the PN. All of these results have led us to suggest that M 1-16 is an
evolved PN, contrary to the scenario of proto-PN suggested in previous studies.
We propose that the mechanism responsible for the morphology of M 1-16 is
related to the binary (or multiple star) evolution scenario.Comment: A&A in press. 11 pages, 9 figure
On the Origin of the -4.4 eV Band in CdTe(100)"
We calculate the bulk- (infinite system), (100)-bulk-projected- and
(100)-Surface-projected Green's functions using the Surface Green's Function
Matching method (SGFM) and an empirical tight-binding hamiltonian with
tight-binding parameters (TBP) that describe well the bulk band structure of
CdTe. In particular, we analyze the band (B--4) arising at --4.4 eV from the
top of the valence band at according to the results of Niles and
H\"ochst and at -4.6 eV according to Gawlik {\it et al.} both obtained by
Angle-resolved photoelectron spectroscopy (ARPES). We give the first
theoretical description of this band.Comment: 17 pages, Rev-TEX, CIEA-Phys. 02/9
Multiple and Precessing Collimated Outflows in the Planetary Nebula IC 4634
With its remarkable double-S shape, IC 4634 is an archetype of
point-symmetric planetary nebulae (PN). In this paper, we present a detailed
study of this PN using archival HST WFPC2 and ground-based narrow-band images
to investigate its morphology, and long-slit spectroscopic observations to
determine its kinematics and to derive its physical conditions and excitation.
The data reveal new structural components, including a distant string of knots
distributed along an arc-like feature 40"-60" from the center of the nebula, a
skin of enhanced [O III]/H-alpha ratio enveloping the inner shell and the
double-S feature, and a triple-shell structure. The spatio-kinematical study
also finds an equatorial component of the main nebula that is kinematically
independent from the bright inner S-shaped arc. We have investigated in detail
the bow shock-like features in IC 4634 and found that their morphological,
kinematical and emission properties are consistent with the interaction of a
collimated outflow with surrounding material. Indeed, the morphology and
kinematics of some of these features can be interpreted using a 3D numerical
simulation of a collimated outflow precessing at a moderate, time-dependent
velocity. Apparently, IC 4634 has experienced several episodes of
point-symmetric ejections oriented at different directions with the outer
S-shaped feature being related to an earlier point-symmetric ejection and the
outermost arc-like string of knots being the relic of an even much earlier
point-symmetric ejection. There is tantalizing evidence that the action of
these collimated outflows has also taken part in the shaping of the innermost
shell and inner S-shaped arc of IC 4634.Comment: 16 pages, 11 figures, accepted for publication in The Astrophysical
Journa
“Desarrollo habitacional preventivo en Mendoza – Instituto de Vivienda Social”
La investigación está dirigida al estudio de las causas determinantes del desarrollo conflictivo delhábitat popular en el gran Mendoza y centros urbanos de la provincia, manifestado en la tomacompulsiva de tierras, edificaciones y viviendas desocupadas por familias en situaciones críticasde vivienda. Abarcada la problemática, la investigación prosigue con la formulación dedirectrices para el establecimiento de políticas socio-habitacionales preventivas de laconflictividad habitacional, de aplicación por los organismos de gobierno, las organizaciones nogubernamentales y las entidades de vivienda de base comunitaria.Como base conceptual de las políticas habitacionales se profundiza sobre el concepto devivienda digna, en función de los requerimientos básicos de habitabilidad humana y los recursospropios de las comunidades con necesidades básicas no satisfechas de vivienda y la asistenciaexterna, técnica y financiera, necesaria para alcanzar soluciones habitacionales sostenibles.La situación actual muestra: i) una permanente repetición de situaciones conflictivas, producto deasentamientos ilegales en situación de carencia; ii) los desalojos forzosos en ocupacionesilegales de bienes inmuebles y la carencia de políticas públicas que prevean la extensión de lasáreas residenciales, haciendo asequible el acceso a la tierra para las familias de bajos ingresos:iii) el insuficiente desarrollo de la capacidad de los gobiernos municipales para atender laproblemática habitacional en forma preventiva.Por tanto existe la necesidad imperiosa de contribuir desde el área de investigación académicaa la solución al problema y el compromiso de las universidades frente a las problemáticassociales agudasLos objetivos generales han sido: planificar el desarrollo habitacional de manera previsible yanticipatoria a las necesidades de espacio habitable digno, acorde con el crecimientopoblacional vegetativo y aportes migratorios, además de colaborar con actores públicos yprivados responsables de la gestión habitacional y contribuir al esclarecimiento del ejercicio delderecho de las comunidades a la habitabilidad en condiciones de decencia y equidad social.Asimismo se pretende promover el acceso a la vivienda social no discriminatoria en morfología,dimensiones y condiciones de habitualidad.Se realizaron mesas de trabajo preparatorias con el IPV y otros actores comprometidos con elproyecto como las cooperativas de vivienda y se formularon las técnicas a utilizar paraelaboración de diagnósticos y pronóstico de la situación habitacional tratada. Se formularonlineamientos estratégicos, conceptuales y metodológicos.de políticas habitacionales de carácterpreventivo y directrices propositivas.Los beneficios del proyecto transfieren a las comunidades y personas afectadas por la crisishabitacional y a la sociedad en general, al reducirse las diferencias en la calidad residencial delos distintos estratos socio-económicos de la población provincial. También a las institucionespúblicas y privadas y comunitarias involucradas en la gestión del hábitat social para la mitigaciónde los conflictos socio-habitacionales, producto de la actual falta de políticas preventivasLos documentos e instrumentos básicos se transfieren a la Cátedra e Instituto de Vivienda Socialy otras unidades académicas de la Universidad de Mendoza como así también a las redesacadémicas y de organizaciones solidarias de hábitat y vivienda
First release of the IPHAS catalogue of new extended planetary nebulae
Date of Acceptance: 30/06/2014We present the first results of our search for new, extended planetary nebulae (PNe) based on careful, systematic, visual scrutiny of the imaging data from the Isaac Newton Telescope Photometric Ha Survey of the Northern Galactic plane (IPHAS). The newly uncovered PNe will help to improve the census of this important population of Galactic objects that serve as key windows into the late-stage evolution of low- to intermediate-mass stars. They will also facilitate study of the faint end of the ensemble Galactic PN luminosity function. The sensitivity and coverage of IPHAS allows PNe to be found in regions of greater extinction in the Galactic plane and/or those PNe in a more advanced evolutionary state and at larger distances compared to the general Galactic PN population. Using a set of newly revised optical diagnostic diagrams in combination with access to a powerful, new, multiwavelength imaging data base, we have identified 159 true, likely and possible PNe for this first catalogue release. The ability of IPHAS to unveil PNe at low Galactic latitudes and towards the Galactic Anticentre, compared to previous surveys, makes this survey an ideal tool to contribute to the improvement of our knowledge of the whole Galactic PN population.Peer reviewe
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