Oxygen and silicon abundances in Cygnus OB2: Chemical homogeneity in a sample of OB slow rotators

Cygnus OB2 is a rich OB association in the Galaxy which has experienced intense star formation in the last 20-25 Myr. Its stellar population shows a correlation between age and Galactic longitude. Exploring the chemical composition of its stellar content we will be able to check the degree of homogeneity of the natal molecular cloud and possible effects of self-enrichment processes. Our aim is to determine silicon and oxygen abundances for a sample of eight early-type slow rotators in Cygnus OB2 in order to check possible inhomogeneities across the whole association and whether there exists a correlation of chemical composition with Galactic longitude. We have performed a spectroscopic analysis of a sample of late O and early B stars with low rotational velocity, which have been chosen so as to cover the whole association area. We have carried out an analysis based on equivalent widths of metal lines, the wings of the H Balmer lines and FASTWIND stellar atmosphere models to determine their stellar fundamental parameters as well as the silicon and oxygen surface abundances. We derive a rather homogeneous distribution of silicon and oxygen abundances across the region, with average values of 12+log(Si/H)=7.53$\pm$0.08 dex and 12+log(O/H)=8.65$\pm$0.12 dex. We find a homogeneous chemical composition in Cygnus OB2 with no clear evidence for significant chemical self-enrichment, despite indications of strong stellar winds and possible supernovae during the history of the region. Comparison with different scenarios of chemical enrichment by stellar winds and supernovae point to star forming efficiencies not significantly above 10%. The degree of homogeneity that we find is consistent with the observed Milky Way oxygen gradient based on HII regions. We also find that the oxygen scatter within Cygnus OB2 is at least of the same order than among HII regions at similar Galactocentric distance.Comment: 15 pages, 7 figures, accepted for publication in Astronomy & Astrophysic

Temporal dispersal patterns of Phaeomoniella chlamydospora, causal agent of Petri disease and esca, in vineyards

[EN] Although the fungus Phaeomoniella chlamydospora is the most commonly detected causal agent of Petri disease and esca, two important fungal grapevine trunk diseases, little is known about the dispersal patterns of P. chlamydospora inoculum. In this work, we studied the dispersal of P. chlamydospora airborne inoculum from 2016 to 2018 in two viticultural areas of eastern (Ontinyent) and northern (Logroño) Spain. The vineyards were monitored weekly from November to April using microscope slide traps, and P. chlamydospora was detected and quantified by a specific real-time quantitative (qPCR) method set up in this work. The method was found to be sensitive, and a good correlation was observed between numbers of P. chlamydospora conidia (counted by microscope) and DNA copy numbers (quantified by qPCR). We consistently detected DNA of P. chlamydospora at both locations and in all seasons but in different quantities. In most cases, DNA was first detected in the last half of November, and most of the DNA was detected from December to early April. When rain was used as a predictor of P. chlamydospora DNA detection in traps, false-negative detections were observed, but these involved only 4% of the total. The dispersal pattern of P. chlamydospora DNA over time was best described (R2 = 0.765 and concordance correlation coefficient = 0.870) by a Gompertz equation, with time expressed as hydrothermal time (a physiological time accounting for the effects of temperature and rain). This equation could be used to predict periods with a high risk of dispersal of P. chlamydosporaFinancial support for carrying out this research was provided by transnational funding bodies, being partners of the H2020 ERA-net project, CORE Organic Cofund, and the Cofund from the European Commission (PCI2018-093015/Project BIOVINE). Part of the research was funded by CAR (Government of La Rioja, Spain), project number R-03-16. C. Berlanas was supported by the FPI-INIA program from the INIA. D. Gramaje was supported by the Ramon y Cajal program, Spanish Government (RYC-2017-23098). Financial support for C. Berlanas during her 1-month stay at Universitat Polit`ecnica de Val`encia was provided by the Viticulture Research Network RedVitis (AGL2015-70931-REDT)González-Domínguez, E.; Berlanas, C.; Gramaje, D.; Armengol Fortí, J.; Rossi, V.; Berbegal Martinez, M. (2020). Temporal dispersal patterns of Phaeomoniella chlamydospora, causal agent of Petri disease and esca, in vineyards. Plant Disease. 110(6):1216-1225. https://doi.org/10.1094/PHYTO-10-19-0400-RS12161225110

Disentangling the spatial substructure of Cygnus OB2 from Gaia DR2

© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical SocietyFor the first time, we have explored the spatial substructure of the Cygnus OB2 association using parallaxes from the recent second Gaia data release. We find significant line-of-sight substructure within the association, which we quantify using a parametrized model that reproduces the observed parallax distribution. This inference approach is necessary due to the non-linearity of the parallax distance transformation and the asymmetry of the resulting probability distribution. Using a Markov Chain Monte Carlo ensemble sampler and an unbinned maximum likelihood test, we identify two different stellar groups superposed on the association. We find the main Cygnus OB2 group at ∼1760 pc, further away than recent estimates have envisaged, and a foreground group at ∼1350 pc. We also calculate individual membership probabilities and identify outliers as possible non-members of the association.Peer reviewe

Fatigue and fracture behavior of composites with metal matrix

Los materiales compuestos son un sistema formado por una mezcla o composición de dos o más micro - macro constituyentes que difieren en forma y composición química y son insolubles entre sí. Las funciones de la matriz en un material compuesto son: - Mantener la armadura en la posición de trabajo y distribuir la carga entre ellos. - Proteger el refuerzo del deterioro mecánico y químico. - Evitar la propagación de grietas. Los materiales compuestos también se pueden clasificar de acuerdo con el tipo de refuerzo. Las propiedades del material compuesto se basan en las propiedades de las fases constituyentes, sus proporciones relativas y la geometría de la armadura, la forma, tamaño, distribución y orientación. Los compuestos de matriz metálica contienen refuerzos cerámicos en una matriz de aleación metálica. La matriz puede ser una aleación de Al o Ti, mientras que los refuerzos pueden ser Al2O3 o SiC. Los compuestos de matriz metálica reforzados con partículas son los más económicos y los más populares. Estos compuestos ofrecen una mayor rigidez, resistencia a temperatura elevada y resistencia al desgaste.Ingeniería Industria

Proposal of Cooperative learning with Moodle

El objetivo de la investigación es mostrar que la utilización de Entornos Virtuales de Aprendizaje dentro de un enfoque constructivista y del aprendizaje cooperativo, permite al alumnado realizar un aprendizaje más globalizado e integrador. Se describen los nuevos roles que hemos de jugar como docentes y como los Entornos Virtuales de Aprendizaje nos permiten asumirlos, incluso sin el contacto diario con el alumno. Veremos también los indicadores que hemos tomado como referencia para esta investigación, que son las diferentes encuestas que se realizaron a los docentes de la Comunidad Valenciana en los cursos del servicio de formación del profesorado.The objective of this research is to show that the use of Virtual Learning Environments within a constructivist paradigm and the collaborative learning, allows students to build an integrated learning. New roles are available for teachers and as Virtual Learning Environments allow us to assume, even without the daily contact with the student. We will also see the indicators used as a reference for this research, which are the different surveys conducted for teachers of Valencia These indicators take into account different aspects that are part of the process of teaching and learning, such as motivation, objectives, content, methodology, evaluation,.

Massive stars in cygnus ob2

Esta tesis es un compendio de tres art´ıculos (m´as un cap´ıtulo adicional) donde se recogen los frutos de un estudio enfocado en Cygnus OB2, una de las asociaciones de formaci´on estelar OB m´as cercana, masiva y joven de nuestra Galaxia. Esta regi´on supone un excelente lugar donde estudiar las propiedades, formaci´on y evoluci´on de estrellas masivas en un entorno de formaci´on estelar muy activo. Nuestro objetivo principal es aumentar el conocimiento que existe actualmente de esta asociaci´on y su poblaci´on estelar. Para ello, hemos llevado a cabo cuatro estudios diferentes (aunque relacionados) d´onde se han caracterizado las principales propiedades f´ısicas de su poblaci´on masiva. En primer lugar presentamos un estudio de membres´ıa en la regi´on de Cygnus OB2 y sus alrededores con el fin de completar la poblaci´on de estrellas de tipo temprano conocida hasta el momento. Haciendo uso de nuevos datos observacionales, hemos incrementado el n´umero de miembros OB de la asociaci´on, a pesar de las limitaciones encontradas para obtener un censo completo. Adem´as, se ha investigado su distribuci´on de edad y extinci´on, as´ı como una posible correlaci´on entre edad y longitud Gal´actica. Dado que existen s´olidas indicaciones que apuntan a que muchas de las estrellas masivas de Cygnus OB2 ya han explotado como supernova a lo largo de su historia, hemos realizado un estudio qu´ımico de la asociaci´on con el prop´osito de detectar posibles inhomogeneidades y comprobar si tambi´en existe una correlaci´on entre composici´on qu´ımica y longitud Gal´actica que pudiera evidenciar procesos de autoenriquecimiento. Un problema persistente en estudios de estrellas masivas ha sido la poca precisi´on en sus distancias. Afortunadamente, el sat´elite Gaia ha proporcionado recientemente astrometr´ıa precisa de un gran n´umero de estrellas masivas Gal´acticas, incluidas aquellas pertenecientes a Cygnus OB2. Por lo tanto, hemos realizado un estudio de su estructura espacial interna, donde se ha cuantificado la subestructura observada a lo largo de la linea de visi´on mediante el uso de inferencia Bayesiana y la creaci´on de un modelo parametrizado que reproduce la distribuci´on de paralaje observada. Finalmente, presentamos el censo espectrosc´opico m´as completo de estrellas O creado hasta el momento en Cygnus OB2. Se han identificado nuevos sistemas binarios, y teniendo en cuenta los resultados derivados de los trabajos anteriores, hemos realizado el an´alisis espectroscopico cuantitativo de todas las estrellas aisladas. Se ha obtenido la distribuci´on de velocidad de rotaci´on y derivado sus principales par´ametros espectrosc´opicos y f´ısicos. Para concluir, se ha interpretado el estado evolutivo de la asociaci´on a partir del diagrama Hertzsprung-Russell (HRD) y su an´alogo espectrosc´opico (sHRD).This thesis is a compendium of three published articles (plus an additional unpublished work) that represents the fruits of research focused on the massive Cygnus OB2 star-forming region. It is one of the nearest, most massive and youngest Galactic OB association and it provides an excellent target to study massive star properties, formation and evolution in a very active environment. Our main goal is to increase our current knowledge of the Cygnus OB2 association and its massive star population. With this aim, we have carried out four different (but related) studies where the main physical properties of the Cygnus OB2 massive population have been characterized. Firstly, we present a membership study of Cygnus OB2 and its surroundings for completing the currently known population of early-type stars in the region. From new spectroscopic observations, we have increased the number of OB stars known in the area in spite of the existing limitations for completing the whole census. We also investigated the age and extinction distribution of the region, and whether there exists a correlation between the observed age spread and Galactic longitude. Since there exist firm indications that many massive stars of Cygnus OB2 have exploded as supernovae during the history of the region, we include a chemical analysis of a sample of OB stars in Cygnus OB2 for checking possible inhomogeneities across the whole association and whether there also exists a correlation of chemical composition with Galactic longitude that could be caused by self-enrichment processes. A persistent problem for massive star studies has been always the inaccuracy of their distances. Fortunately, the second data release of the Gaia satellite has provided high-quality astrometry for a large number of Galactic massive stars, including those in Cygnus OB2. Thus, a study of the spatial substructure of the association is also included in this work, where we have quantified the line-of-sight substructure within the association by using an inference approach and creating a parametrized model that reproduces the observed parallax distribution. Finally, we present the most complete spectroscopic census of O stars done so far in Cygnus OB2. We have updated the binary fraction currently known in the association, and taking into account the results derived in all previous studies, we performed the quantitative spectroscopic analysis of all the isolated stars. We obtained the distribution of rotational velocities and derived physical and spectroscopic parameters, providing new temperature and gravity scales for O-type stars. To conclude, we interpret the evolutionary status of the region using the Hertzsprung-Russell diagram and its spectroscopic version

Fungal trunk pathogens associated with Juglans regia in the Czech Republic

[EN] Juglans regia L. (English walnut) trees with cankers and dieback symptoms were observed in two regions in the Czech Republic. Isolations were made from diseased branches. In total, 138 fungal isolates representing 10 fungal species were obtained from wood samples and identified based on morphological characteristics and molecular methods: Cadophora novi-eboraci, Cadophora spadicis, Cryptovalsa ampelina, Diaporthe eres, Diplodia seriata, Dothiorella omnivora, Eutypa lata, Ewypella sp., Peroneutypa scoparia, and Phaeoacremonium sicilianum. Pathogenicity tests conducted under field conditions with all species using the mycelium-plug method indicated that Eutypa lata and Cadophora spp. were highly virulent to woody stems of walnut. This is the first study to detect and identify fungal trunk pathogens associated with diseased walnut trees in Europe.This work was supported by the Ministerstvo Skolstvi, Mladeze a Telovychovy (EFRR "Multidisciplinary Research to Increase Application Potential of Nanomaterials in Agricultural Practice," project CZ.02.1.01/0.0/0.0/16_025/0007314). This research was also supported by the Technologicka Agentura Ceske Republiky (project TJ02000096)Eichmeier, A.; Pecenka, J.; Spetik, M.; Necas, T.; Ondrasek, I.; Armengol Fortí, J.; León Santana, M.... (2020). Fungal trunk pathogens associated with Juglans regia in the Czech Republic. Plant Disease. 104:761-771. https://doi.org/10.1094/PDIS-06-19-1308-RES76177110

MEGARA-GTC stellar spectral library – II. MEGASTAR first release

MEGARA is an optical integral field and multi-object fibre-based spectrograph for the 10.4 m Gran Telescopio CANARIAS that offers medium-to-high spectral resolutions (FWHM) of R ≃ 6000, 12 000, 20 000. Commissioned at the telescope in 2017, it started operation as a common-user instrument in 2018. We are creating an instrument-oriented empirical spectral library from MEGARA-GTC stars observations, MEGASTAR, crucial for the correct interpretation of MEGARA data. This piece of work describes the content of the first release of MEGASTAR, formed by the spectra of 414 stars observed with R ≃ 20 000 in the spectral intervals 6420–6790 Å and 8370–8885 Å, and obtained with a continuum average signal-to-noise ratio around 260. We describe the release sample, the observations, the data reduction procedure and the MEGASTAR data base. Additionally, we include in Appendix A an atlas with the complete set of 838 spectra of this first release of the MEGASTAR catalogue.This work has been supported by MINECO-FEDER grants AYA2016-75808-R, AYA2016-79724-C4-3-P, RTI2018-096188-BI00, AYA2017-90589-REDT and has been partially funded by FRACTAL, INAOE, and CIEMAT

Spectroscopic characterization of the known O-star population in Cygnus OB2. Evidence of multiple star-forming bursts

Context. Cygnus OB2 provides a unique insight into the high-mass stellar content in one of the largest groups of young massive stars in our Galaxy. Although several studies of its massive population have been carried out over the last decades, an extensive spectroscopic study of the whole known O-star population in the association is still lacking. Aims. We aim to carry out a spectroscopic characterization of all the currently known O stars in Cygnus OB2, determining the distribution of rotational velocities and accurate stellar parameters to obtain an improved view of the evolutionary status of the region. Methods. Based on existing and new optical spectroscopy, we performed a detailed quantitative spectroscopic analysis of all the known O-type stars identified in the association. For this purpose, we used the user-friendly iacob-broad and iacob-gbat automatized tools, FASTWIND stellar models, and astrometry provided by the Gaia second data release. Results. We created the most complete spectroscopic census of O stars carried out so far in Cygnus OB2 using already existing and new spectroscopy. We present the spectra for 78 O-type stars, from which we identify new binary systems, obtain the distribution of rotational velocities, and determine the main stellar parameters for all the stars in the region that have not been detected as double-line spectroscopic binaries. We also derive radii, luminosities, and masses for those stars with reliable Gaia astrometry, in addition to creating the Hertzsprung-Russell Diagram to interpret the evolutionary status of the association. Finally, we inspect the dynamical state of the population and identify runaway candidates. Conclusions. Our spectroscopic analysis of the O-star population in Cygnus OB2 has led to the discovery of two new binary systems and the determination of the main stellar parameters, including rotational velocities, luminosities, masses, and radii for all identified stars. This work has shown the improvement reached when using accurate spectroscopic parameters and astrometry for the interpretation of the evolutionary status of a population, revealing, in the case of Cygnus OB2, at least two star-forming bursts at ~3 and ~5 Myr. We find an apparent deficit of very fast rotators in the distribution of rotational velocities. The inspection of the dynamical distribution of the sample has allowed us to identify nine O stars with peculiar proper motions and discuss a possible dynamical ejection scenario or past supernova explosions in the region.We acknowledge financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) under the grants AYA2012-39364-C02-01, AYA 2015-68012-C2-01, Severo Ochoa SEV-2015-0548 and PGC2018-093741-B-C21/C22 (MICIU/AEI/FEDER, UE)

MEGASTAR - III. Stellar parameters and data products for DR1 late-type stars

© The Authors 2023. This work is part of the grants I+D+i RTI2018-096188-B-I00 and PID2019-107408GB-C41, which have been funded by Ministerio de Ciencia e Innovación and Agencia Estatal de Investigación (MCIN/AEI/10.13039/501100011033). It has been also partially funded by FRACTAL, INAOE and CIEMAT. S.R.B. thanks the financial support by MCIN/AEI/10.13039/501100011033 (contract FJC 2020-045785-I) and NextGeneration EU/PRTR and MIU (UNI/551/2021) through a Margarita Salas grant. This work is based on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos, in the island of La Palma. This work is based on data obtained with MEGARA instrument, funded by European Regional Development Funds (ERDF), through Programa Operativo Canarias FEDER 2014-2020. The authors thank the support given by Dr. Antonio Cabrera and Dr. Daniel Reverte, GTC Operations Group staff, during the preparation and execution of the observations at the GTC. This research made use of Astropy (Astropy Collaboration et al. 2018), a community-developed core Python package for Astronomy. This research has made use of the SIMBAD database and the VizieR catalogue access tool, CDS, Strasbourg, France (DOI: 10.26093/cds/vizier). The original description of the VizieR service was published in A&AS 143, 23. This work has made use of data from the European Space Agency (ESA) mission Gaia (https: //www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos. esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. We are very grateful to the reviewer whose comments and suggestions have helped to improve the manuscript.MEGARA is the optical integral field and multi-object spectrograph at the Gran Telescopio Canarias. We have created MEGASTAR, an empirical library of stellar spectra obtained using MEGARA at high resolution R = 20 000 (FWHM), available in two wavelength ranges: one centered in Hα, from 6420 to 6790 Å and the other centered in the Ca ii triplet, from 8370 to 8885 Å (HR-R and HR-I VPH-grating configurations). In this work, we use MEGASTAR spectra, combination of these two short wavelength intervals, to estimate the stellar parameters namely effective temperature, surface gravity and metallicity (and their associated errors) for a sample of 351 MEGASTAR members with spectral types earlier than B2. We have applied a χ^(2) technique by comparing MEGASTAR data to theoretical stellar models. For those stars with stellar parameters derived in the literature, we have obtained a good agreement between those published parameters and ours. Besides the stellar parameters, we also provide several products like the rectified spectra, radial velocities and stellar indices for this sample of stars. In a near future, we will use MEGASTAR spectra and their derived stellar parameters to compute stellar population evolutionary synthesis models, which will contribute to a better interpretation of star clusters and galaxies spectra obtained with MEGARA.Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEMinisterio de Ciencia e InnovaciónAgencia Estatal de InvestigaciónFRACTALNextGeneration EU/PRTR and MIU through a Margarita Salas grantEuropean Regional Development Funds (ERDF), through Programa Operativo Canarias FEDER 2014-2020INAOECIEMATpu