We consider a small sample of oxygen-rich, asymptotic giant branch stars in the Large Magellanic Cloud, observed by the Spitzer Space Telescope, exhibiting a peculiar spectral energy distribution, ...which can hardly be explained by the common assumption that dust around Asymptotic Giant Branch stars is primarily composed of silicate grains. We suggest that this uncommon class of objects is the progeny of a metal-poor generation of stars, with metallicity Z ∼ 1-2 × 10−3, formed ∼100 Myr ago. The main dust component in the circumstellar envelope is solid iron. In these stars the poor formation of silicates is set by the strong nucleosynthesis experienced at the base of the envelope, which provokes a scarcity of magnesium atoms and water molecules, required for the silicate formation. The importance of the present results to interpret the data from the incoming James Webb Space Telescope is also discussed.
We discuss the evolution of stars through the asymptotic giant branch, focusing on the physical mechanisms potentially able to alter the surface chemical composition and on how changes in the ...chemistry of the external regions affect the physical properties of the star and the duration of this evolutionary phase. We focus on the differences between the evolution of low-mass stars, driven by the growth of the core mass and by the surface carbon enrichment, and that of their higher mass counterparts, which experience hot bottom burning. In the latter sources, the variation of the surface chemical composition reflects the equilibria of the proton capture nucleosynthesis experienced at the base of the convective envelope. The pollution expected from this class of stars is discussed, outlining the role of mass and metallicity on the chemical composition of the ejecta. To this aim, we considered evolutionary models of 0.7–8 M⊙ stars in a wide range of metallicities, extending from the ultra-metal-poor domain to super-solar chemistries.
ABSTRACT
A correlation between astrophysical high-energy neutrinos and blazars has been suggested by various authors. In particular, a likely association between IceCube events and intermediate- and ...high-energy peaked BL Lac objects has led to a sample of 47 objects having a high probability of being neutrino sources. In the first paper of this series we reported optical spectroscopy of 17 objects, which together with data taken from the literature covered 80 per cent of the sample. Here, we present spectroscopy obtained at large aperture telescopes of a further 17 objects (plus four additional targets), which completes the sample coverage. For 12 objects we are able to determine the redshift (0.07 < z < 1.6), while for the others we set a lower limit on it, based on either the robust detection of intervening absorption systems or on an estimation derived from the absence of spectral signatures of the host galaxy. With these new data we expand and reinforce the main results of our previous papers, namely the fact that in terms of their broad-band properties our sources appear to be indistinguishable from the rest of the blazar population and the relatively large (>34 per cent and possibly as high as 80 per cent) fraction of masquerading BL Lac objects, for which the low equivalent width of the emission lines is due to the brightness of the boosted continuum, rather than being an intrinsic property, in our sample.
Gamma-ray bursts (GRBs) are divided into two populations
; long GRBs that derive from the core collapse of massive stars (for example, ref.
) and short GRBs that form in the merger of two compact ...objects
. Although it is common to divide the two populations at a gamma-ray duration of 2 s, classification based on duration does not always map to the progenitor. Notably, GRBs with short (≲2 s) spikes of prompt gamma-ray emission followed by prolonged, spectrally softer extended emission (EE-SGRBs) have been suggested to arise from compact object mergers
. Compact object mergers are of great astrophysical importance as the only confirmed site of rapid neutron capture (r-process) nucleosynthesis, observed in the form of so-called kilonovae
. Here we report the discovery of a possible kilonova associated with the nearby (350 Mpc), minute-duration GRB 211211A. The kilonova implies that the progenitor is a compact object merger, suggesting that GRBs with long, complex light curves can be spawned from merger events. The kilonova of GRB 211211A has a similar luminosity, duration and colour to that which accompanied the gravitational wave (GW)-detected binary neutron star (BNS) merger GW170817 (ref.
). Further searches for GW signals coincident with long GRBs are a promising route for future multi-messenger astronomy.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Context.
The study of stars that evolve through the asymptotic giant branch (AGB) proves crucial in several astrophysical contexts because these objects provide important feedback to the host system ...in terms of the gas that is poured into the interstellar medium after being exposed to contamination from nucleosynthesis processes, and in terms of the dust that forms in their wind. Most of the studies conducted so far have been focused on AGB stars with solar and sub-solar chemical composition, whereas the extremely metal-poor domain has been poorly explored.
Aims.
We study the evolution of extremely metal-poor AGB stars with metallicities down to Fe/H = −5 to understand the main evolutionary properties and the efficiency of the processes able to alter their surface chemical composition, and to determine the gas and dust yields.
Methods.
We calculated two sets of evolutionary sequences of stars in the 1−7.5
M
⊙
mass range that evolved from the pre-main sequence to the end of the AGB phase. To explore the extremely metal-poor chemistries, we adopted the metallicities
Z
= 3 × 10
−5
and
Z
= 3 × 10
−7
, which correspond to Fe/H = −3 and Fe/H = −5, respectively. The results from stellar evolution modelling were used to calculate the yields of the individual chemical species. We also modelled dust formation in the wind to determine the dust produced by these objects.
Results.
The evolution of AGB stars in the extremely metal-poor domain we explored proves highly sensitive to the initial mass of the star.
M
≤ 2
M
⊙
stars experience several third-dredge-up events, which favour the gradual surface enrichment of
12
C and the formation of significant quantities of carbonaceous dust, ∼0.01
M
⊙
. The
13
C and nitrogen yields are found to be significantly smaller than in previous explorations of low-mass metal-poor AGB stars because the proton ingestion episodes experienced during the initial AGB phases are weaker.
M
≥ 5
M
⊙
stars experience hot bottom burning, and their surface chemistry reflects the equilibria of a very advanced proton-capture nucleosynthesis; little dust production takes place in their wind. Intermediate-mass stars experience both third dredge-up and hot bottom burning: they prove efficient producers of nitrogen, which is formed by proton captures on
12
C nuclei of primary origin dredged up from the internal regions.
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FMFMET, NUK, UL, UM, UPUK
Resumen El presente artículo tiene como objetivo principal analizar los rasgos del sentido de vida, motivación y sentido de propósito, como los más influentes en la permanencia en los estudios de un ...grupo de madres adolescentes. Se trabajó desde un paradigma interpretativo, con un enfoque cualitativo y un método fenomenológico; la información se recopiló mediante el uso de técnicas como la entrevista en profundidad y grupos focales, aplicados a once madres adolescentes con edades entre los 14 y 17 años, estudiantes del sistema educativo formal diurno público; pertenecientes a tres instituciones urbanas ubicadas en la Gran Área Metropolitana en los meses de octubre y noviembre de 2015. Los resultados obtenidos permiten identificar los rasgos de sentido de vida: motivación al logro y sentido de propósito como factores determinantes para que estas jóvenes permanezcan estudiando, además se resalta la labor que desde la orientación se puede llevar a cabo con madres adolescentes.
A correlation between astrophysical high-energy neutrinos and blazars has been suggested by various authors. In particular, a likely association between IceCube events and intermediate and ...high-energy peaked BL Lac objects has led to a sample of 47 objects having a high probability of being neutrino sources. In the first paper of this series we reported optical spectroscopy of 17 objects, which together with data taken from the literature covered 80 per cent of the sample. Here we present spectroscopy obtained at large aperture telescopes of a further 17 objects (plus four additional targets), which completes the sample coverage. For twelve objects we are able to determine the redshift (0.07 < z <1.6), while for the others we set a lower limit on it, based on either the robust detection of intervening absorption systems or on an estimation derived from the absence of spectral signatures of the host galaxy. With these new data we expand and reinforce the main results of our previous papers, namely the fact that in terms of their broad-band properties our sources appear to be indistinguishable from the rest of the blazar population and the relatively large (>34 per cent and possibly as high as 80 per cent) fraction of masquerading BL Lac objects, for which the low equivalent width of the emission lines is due to the brightness of the boosted continuum, rather than being an intrinsic property, in our sample.
Los trastornos del espectro autista (TEA) se caracterizan por deficiencias generalizadas en la comunicación social, estereotipias e intereses restringidos. Los TEA presentan una alta prevalencia de ...trastornos psiquiátricos adicionales que empeoran su funcionamiento diario y reducen la calidad de vida de ellos y sus familias.
En el esfuerzo de identificar características ambientales que expliquen esta alta comorbilidad, esta investigación se ha centrado en la sintomatología de estrés y malestar psicológico de los padres como posibles factores de riesgo. Se realizó un estudio transversal de asociación entre estrés y malestar psicológico de padres de niños preescolares con TEA (2-6 años) y su relación con psicopatología coexistente en niños con TEA.
Altos niveles de estrés y malestar psicológico en los padres están asociados ya desde la primera infancia con psicopatología coexistente en dicha población, específicamente con problemas emocionales y conductuales (p < 0,05). Sin embargo, se necesitan futuros estudios longitudinales para entender mejor la relación causal entre estas variables y su posible relación bidireccional.
The Autistic Spectrum Disorders (ASD) are characterised by general deficits in social communication, stereotypes, and restricted interests. The ASD have a high prevalence of additional psychiatric disorders that make their daily functioning worse, and reduces the quality of life of them and their families.
In an effort to identify family environmental characteristics that may influence in the course of additional psychiatric disorders, this study has focused on the symptoms of parental stress and psychological distress as possible risk factors. A cross-section study was carried out on the relationship between the stress and psychological distress of the parents and its relationship with co-existing psychopathology in a population of pre-school children with ASD (2-6 years).
High levels of stress and psychological distress of the parents arealready associated, since early childhood, with co-existing psychiatric symptoms, specifically with emotional and behavioural problems (p < 0.05). However, further longitudinal studies are needed for a better understanding of the causal relationship between these variables and their possible bidirectional relationship.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
La técnica del doble picado no suele utilizarse en el clarinete por la dificultad que entraña. El objetivo es demostrar que la técnica puede ser desempeñada con el clarinete utilizando las TIC. Se ...puso en práctica la técnica en 13 clarinetistas con el Título de Grado Profesional o cursando estudios superiores. Estos la estudiaron mediante 29 ejercicios tras realizar una primera grabación de 2 ejercicios. Tras 8 semanas de estudio se realizó la última grabación para ver si la calidad de la técnica era mayor. La implementación de las TIC consistió en el uso de Audacity (para grabar), Sibelius7 (para escribir los ejercicios), ZyMi (para grabaciones y estudio) y los espectrogramas en Sonic Visualiser de los audios pregrabados (para valorar si existe evolución de la calidad del doble picado). Una vez que fueron analizados los espectrogramas y se escucharon las grabaciones en Sonic Visualiser, se observó que en la primera grabación la calidad del doble picado fue bastante deficiente en los registros agudo y sobreagudo de muchos de los participantes. Sin embargo, en la última grabación todos ellos consiguieron realizar los dos ejercicios con gran calidad en todos los registros. Como conclusión, puede decirse que el doble picado puede ser ejecutado por cualquier clarinetista y que, para ello, es muy recomendable la utilización de las TIC. La utilización de ZyMi y Sonic Visualiser permitió ver en los espectrogramas si la ejecución era precisa en cuanto a tempo, calidad del sonido, articulación, duración e igualdad de las notas.
Aims: We aim to understand the variation of the surface chemistry that occurs during the AGB phase by analysing results from observations of single post-AGB stars in the Magellanic Clouds. We also ...aim at reconstruct dust formation processes, that are active in the circumstellar envelope of AGB stars. Methods: We study likely single post-AGB sources in the Magellanic Clouds that exhibit a double-peaked (shell-type) spectral energy distribution (SED). We interpret their SED by comparing with results from radiative transfer calculations, to derive the luminosity and the dust content of the individual sources. Additionally, we compare the observationally derived stellar parameters and the photospheric chemical abundances of the target sample with results from stellar evolution modelling of AGB and post-AGB stars. This allows for the characterization of the individual sources in terms of initial mass and formation epoch of the progenitors. Results: We find that amongst our target sample of 13 likely single post-AGB stars with shell-type SED, 8 objects are carbon stars descending from ~1-2.5 Msun progenitors. 5 of the 13 objects are of lower mass, descending from M<1 Msun stars. Based on the dust mineralogy, we find that these 5 stars are surrounded by silicate dust, and thus failed to become carbon stars. The dust optical depth and the luminosity of the stars are correlated, owing to the faster evolutionary time-scale brighter stars, which makes the dusty layer to be closer to the central object. From our detailed analysis of the SEDs, we deduce that the dust currently observed around post-AGB stars was released after the onset of the central star contraction and an increase in the effective temperature to ~3500-4000 K.
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