Spectral type, temperature and evolutionary stage in cool supergiants

In recent years, temperature scales in cool supergiants (CSGs) have been disputed, and the possibility that spectral types (SpTs) do not depend primarily on temperature has been raised. We explore the relations between different observed parameters and the capability of deriving accurate intrinsic stellar parameters from them through the analysis of the largest spectroscopic sample of CSGs to date from SMC and LMC. We explore possible correlations between different observational parameters, also making use of near- and mid-infrared colours and literature on photometric variability. Direct comparison between the behaviour of atomic lines (Fe I, Ti I, and Ca II) in the observed spectra and synthetic atmospheric models provides compelling evidence that effective temperature is the prime underlying variable driving the SpT sequence in CSGs. However, there is a clear correlation between SpT and luminosity, with later ones tending to correspond to more luminous stars with heavier mass loss. The population of CSGs in the SMC is characterised by a higher degree of spectral variability, early spectral types (centred on type K1) and low mass-loss rates (at least as measured by dust-sensitive mid-infrared colours). The population in the LMC displays less spectroscopic variability and later spectral types. The distribution of spectral types is not single-peaked. Instead, the brightest CSGs have a significantly different distribution from less luminous objects, presenting mostly M subtypes (centred on M2), and increasing mass-loss rates for later types. In conclusion, the observed properties of CSGs in the SMC and the LMC cannot be described correctly by standard evolutionary models. The very strong correlation between spectral type and bolometric luminosity, supported by all data from the Milky Way, cannot be reproduced at all by current evolutionary tracks.Comment: 25 pages, 24 figure

La arquitectura bioclimática y el cambio climático

La arquitectura siempre había sido bioclimática, pero dejó de serlo en el siglo XX. En caso de volver a ser entendida como tal, podría contribuir a la reducción de emisiones de gases de efecto invernadero. El sector de la construcción, entendiendo por tal todo lo relacionado con la edificación –sin entrar en las obras públicas de infraestructuras, ya que el concepto bioclimático difícilmente se aplicaría a un túnel, un puente o una presa– consume una parte sustancial de la energía y de los recursos producidos, con lo que se convierte en una de las principales fuentes de emisión de gases de efecto invernadero. Si a ello se une el consumo de sectores difusos, como son el consumo doméstico y el del transporte, ambos en gran medida ligados a ese hecho edificatorio, tenemos un panorama en el que se apunta que las acciones más efectivas para reducir las emisiones de CO2 a la atmósfera tiene que ver con las buenas prácticas en el sector de la edificación. La arquitectura bioclimática, que es básicamente la única arquitectura que se ha venido desarrollando por la humanidad hasta la revolución industrial, y la mayoritaria hasta bien entrado el siglo XX, puede mostrar el camino para racionalizar el sector de la construcción y sus efectos en las emisiones de gases de efecto invernadero. Los pasos dados hasta el momento son tímidos, a veces contradictorios, y poco más que anecdóticos en el contexto global, pero tienen la virtud de servir como experimento y como muestra para validar soluciones y elaborar nuevas propuestas. El camino está aún prácticamente por andar

New Cepheid variables in the young open clusters Berkeley 51 and Berkeley 55

As part of a wider investigation of evolved massive stars in Galactic open clusters, we have spectroscopically identified three candidate classical Cepheids in the little-studied clusters Berkeley 51, Berkeley 55 and NGC 6603. Using new multi-epoch photometry, we confirm that Be 51 #162 and Be 55 #107 are bona fide Cepheids, with pulsation periods of 9.83±0.01 d and 5.850±0.005 d respectively, while NGC 6603 star W2249 does not show significant photometric variability. Using the period-luminosity relationship for Cepheid variables, we determine a distance to Be 51 of 5.3 +1.0 −0.8 kpc and an age of 44 +9 −8 Myr, placing it in a sparsely-attested region of the Perseus arm. For Be 55, we find a distance of 2.2±0.3 kpc and age of 63 +12 −11 Myr, locating the cluster in the Local arm. Taken together with our recent discovery of a long-period Cepheid in the starburst cluster VdBH222, these represent an important increase in the number of young, massive Cepheids known in Galactic open clusters. We also consider new Gaia (data release 2) parallaxes and proper motions for members of Be 51 and Be 55; the uncertainties on the parallaxes do not allow us to refine our distance estimates to these clusters, but the well-constrained proper motion measurements furnish further confirmation of cluster membership. However, future final Gaia parallaxes for such objects should provide valuable independent distance measurements, improving the calibration of the period-luminosity relationship, with implications for the distance ladder out to cosmological scales

A quantitative examination of the impact of featured articles in Wikipedia

This paper presents a quantitative examination of the impact of the presentation of featured articles as quality content in the main page of several Wikipedia editions. Moreover, the paper also presents the analysis performed to determine the number of visits received by the articles promoted to the featured status. We have analyzed the visits not only in the month when articles awarded the promotion or were included in the main page, but also in the previous and following ones. The main aim for this is to assess the attention attracted by the featured content and the different dynamics exhibited by each community of users in respect to the promotion process. The main results of this paper are twofold: it shows how to extract relevant information related to the use of Wikipedia, which is an emerging research topic, and it analyzes whether the featured articles mechanism achieve to attract more attention

Temporal characterization of the requests to Wikipedia

This paper presents an empirical study about the temporal patterns characterizing the requests submitted by users to Wikipedia. The study is based on the analysis of the log lines registered by the Wikimedia Foundation Squid servers after having sent the appropriate content in response to users' requests. The analysis has been conducted regarding the ten most visited editions of Wikipedia and has involved more than 14,000 million log lines corresponding to the traffic of the entire year 2009. The conducted methodology has mainly consisted in the parsing and filtering of users' requests according to the study directives. As a result, relevant information fields have been finally stored in a database for persistence and further characterization. In this way, we, first, assessed, whether the traffic to Wikipedia could serve as a reliable estimator of the overall traffic to all the Wikimedia Foundation projects. Our subsequent analysis of the temporal evolutions corresponding to the different types of requests to Wikipedia revealed interesting differences and similarities among them that can be related to the users' attention to the Encyclopedia. In addition, we have performed separated characterizations of each Wikipedia edition to compare their respective evolutions over time

Diferencias de género en una muestra de adolescentes a través de la composición del autoconcepto real e ideal

[Resumen] Cada vez es más común encontrar publi- caciones, trabajos, estudios, tesis…que abor- dan las diferencias de género en la población adulta y menos en adolescentes. En este tra- bajo se han estudiado las diferencias de género en adolescentes a través de la cons- trucción de su autoconcepto. La finalidad de este artículo es comprobar si los participan- tes de este estudio mantienen rasgos consi- derados propios de los hombres para los chi- cos, y rasgos considerados propios de las mujeres para las chicas, y si eso les gustaría que cambiase o no, es decir, comprobar si mantienen o mantendrían los estereotipos de género. Para ello, analizaremos la composi- ción del autoconcepto de los y las adolescen- tes, tanto el autoconcepto real, cómo son, como el ideal, cómo les gustaría ser. El estu- dio se ha realizado con una muestra de 338 adolescentes, 188 chicos y 150 chicas, de la ciudad de Salamanca, estudiantes de Secundaria y con edades comprendidas entre los 12 y los 18 años.[Abstract] Publications, projects, researches and the- sis about gender differences in adult popula- tion are becoming more and more common, the ones about adolescent population aren’t so frequent. In this project, gender differences in adolescent population have been studied through the construction of their self concept. The purpose of this article is to prove if the participants of this project own the characte- ristics that are considered to be typical for men concerning the boys and typical for women concerning the girls, to sum up, to prove if the adolescent population owns or would own the gender stereotypes. Therefore, we have analyzed boys and girls’ self concept, their real self concept, how they are, as well as their ideal one, how they would like to be. The study has been realized with 338 students of Secondary School that are between 12 and 18 years old, 188 boys and 150 girls of the city of Salamanca, Spain

NGC 3105: a young open cluster with low metallicity

NGC 3105 is a young open cluster hosting blue, yellow and red supergiants. This rare combination makes it an excellent laboratory to constrain evolutionary models of high-mass stars. It is poorly studied and fundamental parameters such as its age or distance are not well defined. We intend to characterize in an accurate way the cluster as well as its evolved stars, for which we derive for the first time atmospheric parameters and chemical abundances. We identify 126 B-type likely members within a radius of 2.7$\pm$0.6 arcmin, which implies an initial mass, $M_{cl}\approx$4100 M$_{\odot}$. We find a distance of 7.2$\pm$0.7 kpc for NGC 3105, placing it at $R_{GC}$=10.0$\pm$1.2 kpc. Isochrone fitting supports an age of 28$\pm$6 Ma, implying masses around 9.5 M$_{\odot}$ for the supergiants. A high fraction of Be stars ($\approx$25 %) is found at the top of the main sequence down to spectral type b3. From the spectral analysis we estimate for the cluster a $v_{rad}$=+46.9$\pm$0.9 km s$^{-1}$ and a low metallicity, [Fe/H]=-0.29$\pm$0.22. We also have determined, for the first time, chemical abundances for Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y, and Ba for the evolved stars. The chemical composition of the cluster is consistent with that of the Galactic thin disc. An overabundance of Ba is found, supporting the enhanced $s$-process. NGC 3105 has a low metallicity for its Galactocentric distance, comparable to typical LMC stars. It is a valuable spiral tracer in a very distant region of the Carina-Sagittarius spiral arm, a poorly known part of the Galaxy. As one of the few Galactic clusters containing blue, yellow and red supergiants, it is massive enough to serve as a testbed for theoretical evolutionary models close to the boundary between intermediate and high-mass stars.Comment: 18 pages, 13 figures. Accepted for publication in A&

No surviving evolved companions to the progenitor of supernova SN 1006

Type Ia supernovae are thought to occur as a white dwarf made of carbon and oxygen accretes sufficient mass to trigger a thermonuclear explosion$^{1}$. The accretion could occur slowly from an unevolved (main-sequence) or evolved (subgiant or giant) star$^{2,3}$, that being dubbed the single-degenerate channel, or rapidly as it breaks up a smaller orbiting white dwarf (the double- degenerate channel)$^{3,4}$. Obviously, a companion will survive the explosion only in the single-degenerate channel$^{5}$. Both channels might contribute to the production of type Ia supernovae$^{6,7}$ but their relative proportions still remain a fundamental puzzle in astronomy. Previous searches for remnant companions have revealed one possible case for SN 1572$^{8,9}$, though that has been criticized$^{10}$. More recently, observations have restricted surviving companions to be small, main-sequence stars$^{11,12,13}$, ruling out giant companions, though still allowing the single-degenerate channel. Here we report the result of a search for surviving companions to the progenitor of SN 1006$^{14}$. None of the stars within 4' of the apparent site of the explosion is associated with the supernova remnant, so we can firmly exclude all giant and subgiant companions to the progenitor. Combined with the previous results, less than 20 per cent of type Iae occur through the single degenerate channel.Comment: Published as a letter in Nature (2012 September 27