257 research outputs found

    Fitting isochrones to open cluster photometric data III. Estimating metallicities from UBV photometry

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    The metallicity is a critical parameter that affects the correct determination fundamental characteristics stellar cluster and has important implications in Galactic and Stellar evolution research. Fewer than 10 % of the 2174 currently catalog open clusters have their metallicity determined in the literature. In this work we present a method for estimating the metallicity of open clusters via non-subjective isochrone fitting using the cross-entropy global optimization algorithm applied to UBV photometric data. The free parameters distance, reddening, age, and metallicity simultaneously determined by the fitting method. The fitting procedure uses weights for the observational data based on the estimation of membership likelihood for each star, which considers the observational magnitude limit, the density profile of stars as a function of radius from the center of the cluster, and the density of stars in multi-dimensional magnitude space. We present results of [Fe/H] for nine well-studied open clusters based on 15 distinct UBV data sets. The [Fe/H] values obtained in the ten cases for which spectroscopic determinations were available in the literature agree, indicating that our method provides a good alternative to determining [Fe/H] by using an objective isochrone fitting. Our results show that the typical precision is about 0.1 dex

    Estudo palinostratigráfico do setor Malhadinha, região NE Alvares, concelho de Mértola, Faixa Piritosa Ibérica

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    Cartografia geológica realizada pelo Laboratório Nacional de Energia e Geologia (LNEG) acompanhada por estudos palinostratigráficos na região de Malhadinha, NE de Alvares, localizada no setor WNW da Faixa Piritosa Ibérica (FPI), concelho de Mértola, possibilitaram o conhecimento de detalhe da estratigrafia local. Apresentam-se as idades obtidas por palinologia para as formações Barranco do Homem e Filito-Quartzítica, ambas de idade do Famenniano superior, e Freixial, de idade do Viseano superior, correlacionando-se os dados obtidos com a geologia regional da FPI. Os dados obtidos confirmam o predomínio de estruturas alóctones no setor norte da Faixa Piritosa, entre Alvares e a fronteira espanhola.Geological mapping performed by the National Laboratory of Energy and Geology (LNEG) and palynostratigraphic studies carried out in Malhadinha region, NE of Alvares village, located in the northern sector of the Iberian Pyrite Belt (IPB), WNW of Mértola, allowed to obtain a detailed knowledge of the local stratigraphy. Age data obtained by palynology to the Barranco do Homem (upper Famennian age), Phyllite-Quartzite (upper Famennian age), and Freixial (Visean age), formations are presented and discussed according to the IPB regional geological setting. The age data confirm the predominance of alloctonous tectonic structures in the studied region, in line with previous structural interpretations for the North Sector of the Portuguese part of the Iberian Pyrite Belt.(undefined

    Alterações recentes nas razões isotópicas de Pb em sedimentos do Canhão Submarino de Cascais, Portugal

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    Temporal variations in lead concentrations and stable lead isotopic ratios in two sediment cores from the Cascais Canyon shows changes in sources of Pb during the last two centuries. The increase of total Pb contents wIth the evolution of Pb ratio recorded in both cores reveals the Increase of Pb from industrial sources. Nevertheless, this increase is lower in deeper core location (252-32) due to dilution and mixing with uncontaminated marine materials. An isotopic shift towards lower Pb/Pb in the shallower core (252-35) during the 1970s may reflect the increasing number of vehicles in the Lisboa area during that time

    A Multi-Analytical study of Rock Paintings from Leandro 5 Megalithic Barrow, North-Weastern Portugal

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    The colourant composition of a northern Portugal megalithic barrow decorated with ‘solar’ motifs was studied using a multi-analytical approach, allowing the characterisa- tion of the painting techniques, pigments and binders. The red pigment was prepared with iron oxide minerals, using vegetal oils as organic additives, while the black pigment was char- coal without any organic additives or binders. The solar motif was first drawn with charcoal and subsequently painted with a red pigment.The work was supported by UID/QUI/50006/2019 with funding from FCT/MCTES through national funds. César Oliveira acknowledges Instituto de Ciências e Tecnologias Agrárias e Agro-Alimentares, Porto (ICETA), for his contract under project NORTE-01-0145-FEDER-000011. This work was also developed under the project ‘Funerary and ceremonial practices between the Neolithic and the Bronze Age approached by archaeometry’ (ARQUEOM/Project-Sept2014)
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