Asteroseismology of delta Scuti stars in open clusters: Praesepe

The present paper provides a general overview of the asteroseismic potential of delta Scuti stars in clusters, in particular focusing on convection diagnostics. We give a summarise of the last results obtained by the authors for the Praesepe cluster of which five delta Scuti stars are analysed. In that work, linear analysis is confronted with observations, using refined descriptions for the effects of rotation on the determination of the global stellar parameters and on the adiabatic oscillation frequency computations. A single, complete, and coherent solution for all the selected stars is found, which lead the authors to find important restrictions to the convection description for a certain range of effective temperatures. Furthermore, the method used allowed to give an estimate of the global parameters of the selected stars and constrain the cluster.Comment: 6 pages, 1 figure. Accepted for publication in Communications in Asteroseismolog

Measuring mean densities of delta Scuti stars with asteroseismology. Theoretical properties of large separations using TOUCAN

We aim at studying the theoretical properties of the regular spacings found in the oscillation spectra of delta Scuti stars. We performed a multi-variable analysis covering a wide range of stellar structure and seismic properties and model parameters representative of intermediate-mass, main sequence stars. The work-flow is entirely done using a new Virtual Observatory tool: TOUCAN (the VO gateway for asteroseismic models), which is presented in this paper. A linear relation between the large separation and the mean density is predicted to be found in the low frequency frequency domain (i.e. radial orders spanning from 1 to 8, approximately) of the main-sequence, delta Scuti stars' oscillation spectrum. We found that such a linear behavior stands whatever the mass, metallicity, mixing length, and overshooting parameters considered in this work. The intrinsic error of the method is discussed. This includes the uncertainty in the large separation determination and the role of rotation. The validity of the relation found is only guaranteed for stars rotating up to 40 percent of their break-up velocity. Finally, we applied the diagnostic method presented in this work to five stars for which regular patterns have been found. Our estimates for the mean density and the frequency of the fundamental radial mode match with those given in the literature within a 20 percent of deviation. Asteroseismology has thus revealed an independent direct measure of the average density of delta Scuti stars, analogous to that of the Sun. This places tight constraints on the mode identification and hence on the stellar internal structure and dynamics, and allows a determination the radius of planets orbiting around delta Scuti stars with unprecedented precision. This opens the way for studying the evolution of regular patterns in pulsating stars, and its relation with stellar structure and evolution.Comment: 11 pages, 6 figures, A&A in pres

CNO behaviour in planet-harbouring stars. II. Carbon abundances in stars with and without planets using the CH band

Context. Carbon, oxygen and nitrogen (CNO) are key elements in stellar formation and evolution, and their abundances should also have a significant impact on planetary formation and evolution. Aims. We present a detailed spectroscopic analysis of 1110 solar-type stars, 143 of which are known to have planetary companions. We have determined the carbon abundances of these stars and investigate a possible connection between C and the presence of planetary companions. Methods. We used the HARPS spectrograph to obtain high-resolution optical spectra of our targets. Spectral synthesis of the CH band at 4300\AA was performed with the spectral synthesis codes MOOG and FITTING. Results. We have studied carbon in several reliable spectral windows and have obtained abundances and distributions that show that planet host stars are carbon rich when compared to single stars, a signature caused by the known metal-rich nature of stars with planets. We find no different behaviour when separating the stars by the mass of the planetary companion. Conclusions. We conclude that reliable carbon abundances can be derived for solar-type stars from the CH band at 4300\AA. We confirm two different slope trends for [C/Fe] with [Fe/H] because the behaviour is opposite for stars above and below solar values. We observe a flat distribution of the [C/Fe] ratio for all planetary masses, a finding that apparently excludes any clear connection between the [C/Fe] abundance ratio and planetary mass.Comment: 10 pages, 10 figures. Accepted to A&

C/O vs Mg/Si ratios in solar type stars: The HARPS sample

Aims. We present a detailed study of the Mg/Si and C/O ratios and their importance in determining the mineralogy of planetary companions. Methods. Using 499 solar-like stars from the HARPS sample, we determine C/O and Mg/Si elemental abundance ratios to study the nature of the possible planets formed. We separated the planetary population in low-mass planets ( < 30 $\rm M_{\odot}$) and high-mass planets ( > 30 $\rm M_{\odot}$) to test for possible relation with the mass. Results. We find a diversity of mineralogical ratios that reveal the different kinds of planetary systems that can be formed, most of them dissimilar to our solar system. The different values of the Mg/Si and C/O ratios can determine different composition of planets formed. We found that 100\% of our planetary sample present C/O < 0.8. 86\% of stars with high-mass companions present 0.8 > C/O > 0.4, while 14\% present C/O values lower than 0.4. Regarding Mg/Si, all stars with low-mass planetary companion showed values between 1 and 2, while 85% of the high-mass companion sample does. The other 15\% showed Mg/Si values below 1. No stars with planets were found with Mg/Si > 2. Planet hosts with low-mass companions present C/O and Mg/Si ratios similar to those found in the Sun, whereas stars with high-mass companions have lower C/O.Comment: 9 pages, 12 figues. Accepted in A&

Situación de los recursos hídricos en Nicaragua

Nicaragua, conocido como el país de lagos y volcanes, es abundante en recursos hídricos superficiales y subterráneos. Sus dos grandes lagos de origen tectónico, Xolotlán de 1.040 km2 y Cocibolca de 8.200 km2; sus 21 cuencas hidrográficas con un potencial de 152.596 millones de m3; un sinnúmero de lagunas de origen volcánico y dos lagos artificiales forman parte de sus riquezas. En la Región del Pacífico se desarrollan los acuíferos de mayor potencial mientras que en la región Atlántica la abundancia de recursos hídricos superficiales ha relegado el desarrollo de los subterráneos. En esta zona del Pacífico se concentra la mayor densidad poblacional y es donde se realiza la mayor actividad agrícola e industrial del país; lo que ha conllevado, en algunos casos a la explotación excesiva de los acuíferos, y a una degradación progresiva de la calidad del agua, que amenaza la disponibilidad futura de agua para usos vitales de la población. Se han encaminado esfuerzos en la solución a estos problemas, con un enfoque integral de cuencas, que actualmente está poco a poco resultando en conservación y restauración de las recursos hídricos

Experimental measurement of the quality factor of a Fabry-P\'erot open-cavity axion haloscope

The axion is a hypothetical boson arising from the most natural solution to the problem of charge and parity symmetry in the strong nuclear force. Moreover, this pseudoscalar emerges as a dark matter candidate in a parameter space extending several decades in mass. The Dark-photons \& Axion-Like particles Interferometer (DALI) is a proposal to search for axion dark matter in a range that remains under-examined. Currently in a design and prototyping phase, this haloscope is a multilayer Fabry-P\'erot interferometer. A proof-of-principle experiment is performed to observe the resonance in a prototype. The test unveils a quality factor per open cavity of a few hundred over a bandwidth of the order of dozens of megahertz. The result elucidates a physics potential to find the, so far elusive, axion, in a sector which can simultaneously solve the symmetry problem in the strong interaction and the enigma of dark matter.Comment: 5 pages, 6 figure

Intelligent control of temperature with dynamic voltage-frequency scaling (DVFS) in embedded processors

[EN] The increment in computing power of embedded processors has fueled a revolution in many application domains such as mobile computing or robotics. Dissipating the energy consumed by those processors on a very small area has made power management a first-order constraint. On one hand, it is impossible to directly apply active dissipation techniques. On the other hand, design requirements prevent the correct behaviour of known passive detection techniques. To alleviate this problem, we present a new control approach to keep the temperature of the system controlled through the Dynamic Voltage and Frequency Scaling (DVFS) system. The solution includes a feedback control scheme together with a supervisor that adjusts the control parameters based on the system load. To ease experimentation without compromising real use, the code can run in user space and as a Linux kernel driver. The experiments in a real platform prove that, compared to the current control methodology, our approach handles the processor’s temperature with more precision, keeping similar performance levels in the execution of well known benchmarks.[ES] El aumento de la capacidad de cálculo de los procesadores embebidos ha generado una revolución en numerosos dominios de aplicación como la computación móvil o la robótica. La disipación del consumo producido por estos cálculos en una superficie tan pequeña hace que la disipación de energía suponga un problema de primer orden. Por un lado, no es posible aplicar técnicas de disipación activas y, por otro, las exigencias de diseño impiden una correcta disipación pasiva. Para resolver este problema, este trabajo presenta una metodología de control para el mantenimiento de una temperatura bajo control mediante el uso de escalado dinámico de la frecuencia del procesador (DVFS, Dynamic Voltage Frequency Scaling). La solución incluye un esquema de control de temperatura basado en realimentación junto con un supervisor que ajusta los parámetros del controlador en base al tipo de carga del trabajo. La estrategia de control propuesta se ha implementado tanto en espacio de usuario como driver dentro del kernel de Linux. Los experimentos realizados en una plataforma real demuestran que, comparado con el control existente en la actualidad, nuestra propuesta es capaz de gestionar la temperatura del procesador con más precisión, manteniendo niveles similares de eficiencia en la ejecución de benchmarks conocidos.Este artículo ha sido financiado parcialmente por los proyectos PGC2018-098817-A-I00 (MCIU/AEI/FEDER, UE), MIG20201006, PID2019-105660RB-C21 ( MINECO/AEI/FEDER), Grupos T58 20R y T45 20R ( Gobierno de Aragón) y FEDER 2014-2020 “Construyendo Europa desde Aragón”. Los autores agradecen el apoyo recibido.Hernández-Almudi, P.; Suárez, D.; Montijano, E.; Merino, J. (2021). 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