Metalicidad de estrellas gigantes con planetas

Presentamos 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

Possible chromospheric activity cycles in AD Leo

AD Leo (GJ 388) is an active dM3 flare star extensively observed both in the quiescent and flaring states. Since this active star is near the fully-convective boundary, to study in detail its long-term chromospheric activity could be an appreciable contribution for the dynamo theory. Here, we analyze with the Lomb-Scargle periodogram the Ca II K line-core fluxes derived from CASLEO spectra obtained between 2001 and 2013 and the V magnitude from the ASAS database between 2004 and 2010. From both totally independent time-series, we obtain a possible activity cycle of period $\sim7$ years and a less-significant shorter one of $\sim2$ years. A tentative interpretation is that a dynamo operating near the surface could be generating the longer cycle, while a second dynamo operating in the deep convection zone could be responsible for the shorter one. Based on the long duration of our observing program at CASLEO and the fact that we observe simultaneously different spectral features, we also analyze the relation between simultaneous measurements of the Na I index ($R^{\prime}_D$), H$\alpha$ and Ca II K fluxes at different activity levels of AD Leo, including flares.Comment: 21 pages, 3 figures.Accepted for publication in ApJ

Estrellas evolucionadas con planetas : abundancias químicas y propiedades planetarias

Tesis (Doctor en Astronomía)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía y Física, 2015.Actualmente es un hecho aceptado que las estrellas de secuencia principal que albergan planetas gigantes son, en promedio, más ricas en metales que aquéllas sin planetas detectados. Sin embargo, en el caso de las estrellas evolucionadas, especialmente las gigantes, los resultados han sido más dispares o controversiales por lo que el tema permanece abierto. Por otro lado, aún se debate fuertemente si las estrellas de secuencia principal con planetas gigantes poseen menor abundancia de litio que aquéllas sin planetas detectados. El estudio de las abundancias químicas de varios elementos, como así también la exploración de sus relaciones con las propiedades planetarias cuenta con varios antecedentes en estrellas de secuencia principal con planetas, pero sólo se ha realizado ocasionalmente en estrellas evolucionadas con planetas. Este tipo de estudios es fundamental tanto para identificar las variables observables que controlan el proceso de formación y evolución de los sistemas planetarios, como también para estudiar el efecto de la formación planetaria en la estructura y evolución de las estrellas huéspedes. Así, en este trabajo presentamos parámetros fundamentales y abundancias químicas de 15 elementos para una muestra de 223 estrellas evolucionadas, incluyendo 86 con planetas. A partir de estos parámetros analizamos: i) diferencias químicas entre estrellas con y sin planetas; ii) diferencias entre las propiedades de los planetas alrededor de gigantes y subgigantes; y iii) correlaciones entre las propiedades planetarias y las abundancias químicas de sus estrellas huéspedes

Fish toxicity of commercial herbicides formulated with glyphosate

We report here the acute and chronic toxicity of two commercial formulations of herbicides whose active ingredient is glyphosate (Glacoxan® and Estrella®). The acute toxicity was tested toward two fish species Danio rerio and Poecilia reticulata by evaluating the mortality. The chronic toxicity was assessed in D. rerio by measuring the biochemical parameters glutamic pyruvic transaminase (AST) and glutamic oxaloacetic transaminase (ASL). In addition the analysis of haematological parameters (morphological study) was carried out. The results indicate that both herbicides produce acute toxicity toward the two tested species. In addition the biochemical parameters displayed high values as a sign of chronic toxicity. Thereby, indicating that both herbicides may produce environmental damage.Fil: Jofré, Diego Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia; ArgentinaFil: Germanó García, María José. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia; ArgentinaFil: Salcedo, Rodrigo Emiliano. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Morales, Mirta. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia; ArgentinaFil: Alvarez, María. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia; ArgentinaFil: Enriz, Ricardo Daniel. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gianinni, Fernando. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia; Argentin

A compositional link between rocky exoplanets and their host stars

Stars and planets both form by accreting material from a surrounding disk. Because they grow from the same material, theory predicts that there should be a relationship between their compositions. In this study, we search for a compositional link between rocky exoplanets and their host stars. We estimate the iron-mass fraction of rocky exoplanets from their masses and radii and compare it with the compositions of their host stars, which we assume reflect the compositions of the protoplanetary disks. We find a correlation (but not a 1:1 relationship) between these two quantities, with a slope of >4, which we interpret as being attributable to planet formation processes. Super-Earths and super-Mercuries appear to be distinct populations with differing compositions, implying differences in their formation processes.Comment: Authors' version of the manuscript. Published in Scienc

Evaluation of an Active Humidification System for Inspired Gas

ObjectivesThe effectiveness of the active humidification systems (AHS) in patients already weaned from mechanical ventilation and with an artificial airway has not been very well described. The objective of this study was to evaluate the performance of an AHS in chronically tracheostomized and spontaneously breathing patients.MethodsMeasurements were quantified at three levels of temperature (T°) of the AHS: level I, low; level II, middle; and level III, high and at different flow levels (20 to 60 L/minute). Statistical analysis of repeated measurements was performed using analysis of variance and significance was set at a P<0.05.ResultsWhile the lowest temperature setting (level I) did not condition gas to the minimum recommended values for any of the flows that were used, the medium temperature setting (level II) only conditioned gas with flows of 20 and 30 L/minute. Finally, at the highest temperature setting (level III), every flow reached the minimum absolute humidity (AH) recommended of 30 mg/L.ConclusionAccording to our results, to obtain appropiate relative humidity, AH and T° of gas one should have a device that maintains water T° at least at 53℃ for flows between 20 and 30 L/m, or at T° of 61℃ at any flow rate