1,721,000 research outputs found
Metalicidad de estrellas gigantes con planetas
Full text linkPresentamos una determinación homogénea de metalicidades correspondiente a 31 estrellas gigantes (incluyendo 5 que albergan planetas) con el objetivo de verificar los recientes resultados que establecen que la metalicidad de este tipo de objetos podría depender de la lista de líneas espectrales utilizada y por lo tanto haber llevado a distintos grupos a subestimar o sobreestimar la metalicidad para este tipo de objetos (Santos et al. 2009). Además, comparamos la distribución de metalicidad de las estrellas gigantes con la obtenida para 22 estrellas de secuencia principal con planetas y analizamos los resultados en el marco de las hipótesis más importantes que explican el alto contenido metálico de las estrellas enanas que albergan planetas gigantes.We present an homogeneous metallicity determination for 31 giant stars (including 5 exoplanet host) to confirm recent results that stablish the metallicity of this kind of objects could depend on the spectral line list and therefore it could be the responsable for overestimating or subestimating the metallicity of these objects (Santos et al. 2009). Furthermore, we compare the giant stars metallicity distribution with a 22 main-sequence exoplanet host-stars’s and analyze our results in the context of the most important hypothesis that explain the high metal content of main-sequence stars with giant planets.Fil: Jofré, Emiliano. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Saffe, Carlos. Consejo Nacional de Investigaciones Cientiâficas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; Argentina. Universidad Nacional de San Juan; Argentin
Elemental abundance studies of CP stars. The Silicon stars HD 87405 and HD 146555
Full text linkIn this paper we present an analysis of the Ap(Si) stars HD 87405 and HD 146555 using an ATLAS9 model atmospheres. These Chemically Peculiar (CP) stars belong to the southern hemisphere open clusters NGC 3114 and NGC 6087, respectively. For HD 87405 and HD 146555, C and Ca (only one line) are mostly solar, Mg and S are slightly underabundant, while Si is overabundant by factors between ? 4-6. Heavier elements are all overabundant, Ti, Cr by factors of ? 50, while Mn is nearly ? 50 and ? 120 times overabundant for HD 87405 and HD 146555, respectively. Fe is ? 10 times solar, Sr, Y, Zr are overabundant by factors between ? 100-1000 and rare earth by factors of ? 1000 or more. This work is part of our current study for verifying a possible tendence of abundances with the age of CP stars in open clusters.Fil: Saffe, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Levato, Orlando Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; Argentin
Metalicidad de estrellas con exoplanetas y discos de polvo
Full text linkWe present an uniform comparison among three different kind of objects: cool-Jupiter exoplanet host-stars, stars with dust disks and exoplanet host-stars with dust disks. The goal of this contribution was to determine why stellar objects originally surrounded by planetesimals evolve to different final configurations, from stars with planets to stars with debris disks.Realizamos una comparación uniforme de las metalicidades de tres grupos de objetos diferentes: estrellas con planetas del tipo Júpiter frío, estrellas con discos de polvo y estrellas que poseen tanto planetas como discos de polvo. El objetivo de esta contribución fue el de indagar sobre los motivos por los cuales objetos estelares que originalmente son circundados por planetesimales, evolucionan hacia configuraciones finales distintas, que van desde estrellas con compañeras de masa planetaria hasta estrellas rodeadas por discos de partículas sólidas.Fil: Petrucci, Romina Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio(i); ArgentinaFil: Saffe, Carlos. Consejo Nacional de Investigaciones Cientiâficas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales; ArgentinaFil: Jofré, E.. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
CN and CH bands in Exoplanet Host Stars
Full text linkEn este trabajo medimos la intensidad de las bandas moleculares CN y CH en una muestra de estrellas con y sin exoplanetas (indices δS3839, δS4142 y δCH4300). El índice δS3839 parece ser menor en estrellas sin exoplanetas. El hecho de que la banda CN aumente con la metalicidad, puede explicar al menos en parte las diferentes distribuciones observadas en estrellas con y sin exoplanetas. Advertimos que hasta el momento las muestras son relativamente pequeñas.We measured the strength of CN and CH molecular bands in a sample of stars with and without exoplanets (indices δS3839, δS4142 and δCH4300). The index δS3839 seem to present smaller values for stars without exoplanets. No correlation is found between molecular bands and exoplanet parameters, supporting the primordial hypothesis of planet formation. The CN band strength seem to increase with C, N and Fe abundances. This could explain at least in part the dissimilar distributions of CN observed for stars with and without exoplanets. We caution that this is an initial result based in relatively small number of objects.Fil: Saffe, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Jofre, Jorge Emiliano. Universidad Nacional de Córdoba; ArgentinaFil: Petrucci, Romina. Universidad Nacional de Córdoba; Argentin
Line Identification of the Si Star HD 87240
Full text linkLine identifications are presented for the peculiar Apstar HD7240 (delta = - 59° 51´ 00.1´´) in the spectral region lambdalambda 3710-5520. This object is a member of the southern open cluster NGC114. Comparison of this object with other field silicon stars shows that it shares many of their line anomalies.Se presentan las identificaciones de las líneas de la estrella peculiar tipo Ap Si HD 87240 ( δ = − 59 ◦ 51 0 00 . 1 00 ) en el intervalo espectral λλ3710–5520. Este objeto es miembro del cúmulo abierto meridional NGC 3114. La comparación de este objeto con otras estrellas Ap Si del campo muestra que tienen en común muchas de las anomalías en sus líneas.Fil: Saffe, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Levato, Orlando Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: López García, Z.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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