Probing the Large Magellanic Cloud's recent chemical enrichment history through its star clusters

We present Washington system colour-magnitude diagrams (CMDs) for 17 practically unstudied star clusters located in the bar as well as in the inner disc and outer regions of the Large Magellanic Cloud (LMC). Cluster sizes were estimated from star counts distributed throughout the entire observed fields. Based on the best fits of theoretical isochrones to the cleaned $(C-T_1,T_1)$ CMDs, as well as on the $\delta T_1$ parameter and the standard giant branch method, we derive ages and metallicities for the cluster sample. Four objects are found to be intermediate-age clusters (1.8-2.5 Gyr), with [Fe/H] ranging from -0.66 to -0.84. With the exception of SL263, a very young cluster ($\sim$ 16 Myr), the remaining 12 objects are aged between 0.32 and 0.89 Gyr, with their [Fe/H] values ranging from -0.19 to -0.50. We combined our results with those for other 231 clusters studied in a similar way using the Washington system. The resulting age-metallicity relationship shows a significant dispersion in metallicities, whatever age is considered. Although there is a clear tendency for the younger clusters to be more metal-rich than the intermediate ones, we believe that none of the chemical evolution models currently available in the literature reasonably well represents the recent chemical enrichment processes in the LMC clusters. The present sample of 17 clusters is part of our ongoing project of generating a database of LMC clusters homogeneously studied using the Washington photometric system and applying the same analysis procedureComment: 11 pages, 20 figures, 3 tables, Accepted for publication in MNRA

A sample of relatively unstudied star clusters in the Large Magellanic Cloud: fundamental parameters determined from Washington photometry

To enlarge our growing sample of well-studied star clusters in the Large Magellanic Cloud (LMC), we present CCD Washington CT1 photometry to T1 ~ 23 in the fields of twenty-three mostly unstudied clusters located in the inner disc and outer regions of the LMC. We estimated cluster radii from star counts. Using the cluster Washington (T1,C-T1) colour-magnitude diagrams, statistically cleaned from field star contamination, we derived cluster ages and metallicities from a comparison with theoretical isochrones of the Padova group. Whenever possible, we also derived ages using delta_T1 - the magnitude difference between the red giant clump and the main sequence turn off - and estimated metallicities from the standard giant branch procedure. We enlarged our sample by adding clusters with published ages and metallicities determined on a similar scale by applying the same methods. We examined relationships between their positions in the LMC, ages and metallicities. We find that the two methods for age and metallicity determination agree well with each other. Fourteen clusters are found to be intermediate-age clusters (1-2 Gyr), with [Fe/H] values ranging from -0.4 to -0.7. The remaining nine clusters turn out to be younger than 1 Gyr, with metallicities between 0.0 and -0.4. Our 23 clusters represent an increase of ~ 30% in the current total amount number of well-studied LMC clusters using Washington photometry. In agreement with previous studies, we find no evidence for a metallicity gradient. We also find that the younger clusters were formed closer to the LMC centre than the older ones.Comment: 11 pages, 10 figures. A&A, in pres

Photometric observations and Coravel radial velocities of red giant candidates in open clusters

Presentamos fotometrıa fotoelectrica multicolor de alta precision y velocidades radiales (VRs) Coravel para una muestra de candidatas a gigantes rojas (GRs) en nueve cumulos abiertos galacticos. Encontramos que aproximadamente el 82 % de las estrellas analizadas son GRs de los cumulos, de acuerdo a criterios fotometricos, en excelente acuerdo con los resultados inferidos a partir de las VRs Coravel. Se determinan excesos de color E(B − V ), temperaturas efectivas y metalicidades para las gigantes de los cumulos. Una nueva binaria espectroscopica fue descubierta entre las GRs de NGC 2482.We present high precision multicolour photoelectric photometry together with Coravel radial-velocity data for a sample of red giant (RG) candidates in nine Galactic open clusters. Nearly 82% of the analized stars are found to be cluster RGs from photometric criteria, in excellent agreement with the Coravel membership probabilities. E(B − V ) colour excesses, effective temperatures and metallicities are derived for the cluster giants. A new spectroscopic binary was discovered among the RGs of NGC 2482.Fil: Claria Olmedo, Juan Jose. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Mermilliod, J. C.. Ecole Polytechnique Federale de Lausanne; FranciaFil: Palma, T.. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentin

Raman-scattered O VI Features in the Symbiotic Nova RR Telescopii

RR Tel is an interacting binary system in which a hot white dwarf (WD) accretes matter from a Mira-type variable star via gravitational capture of its stellar wind. This symbiotic nova shows intense Raman-scattered O VI 1032 and 1038 features at 6825 ˚A and 7082 ˚A. We present high-resolution optical spectra of RR Tel taken in 2016 and 2017 with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph at Magellan-Clay telescope, Chile. We aim to study the stellar wind accretion in RR Tel from the profile analysis of Raman O VI features. With an asymmetric O VI disk model, we derive a representative Keplerian speed of > 35 km s−1 , and the corresponding scale < 0.8 au. The best-fit for the Raman profiles is obtained with a mass loss rate of the Mira M˙ ∼ 2 × 10−6 M yr−1 and a wind terminal velocity v∞ ∼ 20 km s−1 . We compare the MIKE data with an archival spectrum taken in 2003 with the Fibre-fed Extended Range Optical Spectrograph (FEROS) at the MPG/ESO 2.2 m telescope. It allows us to highlight the profile variation of the Raman O VI features, indicative of a change in the density distribution of the O VI disk in the last two decades. We also report the detection of O VI recombination lines at 3811 ˚A and 3834 ˚A, which are blended with other emission lines. Our profile decomposition suggests that the recombination of O VII takes place nearer to the WD than the O VI 1032 and 1038 emission region.Fil: Heo, J. E.. Observatorio Gemini; Chile. Universidad de La Serena; Chile. Sejong University; Corea del SurFil: Lee, H. W.. Universidad de Sejong; Corea del SurFil: Angeloni, R.. Universidad de La Serena; ChileFil: Palma, Tali. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Di Mille, F.. Observatorio Las Campanas; Chil

Determinación espectroscópica de parámetros fundamentales de 18 cúmulos abiertos de pequeño diámetro angular

Following specific criteria, we have carefully selected objects catalogued as open cluster candidates. Out of a total of 58 small angular diameter selected objects without previous studies, we obtained integrated spectra of 18 of them at CASLEO (San Juan, Argentina). Using a computational tool specially developed for the analysis of integrated spectra, reddenings and ages of the observed clusters were determined for the first time.Hemos realizado una cuidadosa seleccion de objetos catalogados como candidatos a cumulos abiertos siguiendo criterios especıficos. De un total de 58 objetos de peque˜no diametro angular seleccionados sin estudios previos, hemos obtenido espectros integrados de 18 de ellos en el CASLEO (San Juan, Argentina). Utilizando una herramienta computacional especıficamente desarrollada para el analisis de espectros integrados, hemos determinado por primera vez enrojecimientos y edades de los cumulos observados.Fil: Benítez Llambay, Alejandro. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Claria Olmedo, Juan Jose. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Palma, Tali. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ahumada, Andrea Veronica. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

CCD Washington photometry of ten open clusters or candidates projected close to the galactic plane

We present high-quality CCD photometry in the Washington system C and T1 passbands down to T1 ≈ 19.5 mag in the fields of ten Galactic open clusters or candidates projected close to the Galactic plane, namely: ESO 313-SC03, BH 54, Ruprecht 87, ESO 129-SC32, BH 217, Collinder 347, Basel 5, Ruprecht 144, Archinal 1 and Berkeley 82. Four of these objects are located toward the Galactic center within a solid angle of 21 ◦ . No photoelectric or CCD photometry in the optical domain has been so far reported for five of these objects. Cluster radii are estimated from radial density profiles in the cluster fields. Using the cluster Washington (C−T1 , T1 ) color-magnitude diagrams, statistically cleaned from field star contamination, we estimate reddening, heliocentric distance and age of the clusters by fitting Padova theoretical isochrones computed for the Washington system. In all cases, the best fittings were obtained with nearly solar metal content isochrones. Both radial density profiles and color-magnitude diagrams show that we are dealing with real open clusters, except for Ruprecht 87 and Archinal 1 that are found to be probably not physical systems. Differential reddening appears to be present across the fields of ESO 313-SC03, ESO 129-SC32, BH 217, Collinder 347 and Basel 5. The studied open clusters are located at d = 1.0−5.0 kpc from the Sun and at Galactocentric distances RGC = 6.0−10.6 kpc, with mean reddening E(B − V ) in the range of 0.10-1.30 mag and ages between 5 Myr (Collinder 347) and ≈ 1000 Myr (Basel 5). The estimated linear cluster radii are in the range of 0.4-3.2 pc. In general terms, the results obtained show fairly good agreement with previous photometric results. In some clusters, however, considerable differences are found between the present results and previous ones determined using near-infrared photometric data. The current study provides new open cluster parameters and some revisions to the open cluster catalogs.Fil: Claria Olmedo, Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; ArgentinaFil: Parisi, Maria Celeste. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Palma, Tali. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; ArgentinaFil: Ahumada, Andrea Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; ArgentinaFil: Oviedo, Carla Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

Determinación de parámetros fundamentales de dos cúmulos abiertos del cuarto cuadrante galáctico en base a fotometría de Washington

We present preliminary results obtained from a photometric analysis in the Washington system C and T1 passbands of two poorly known open clusters (OCs) located in the fourth Galactic quadrant: BH 84 and BH 211. Based on the best fits of theoretical isochrones to the (T1, C −T1) colour- magnitude diagrams, we derive the fundamental cluster parameters. The present results are part of a major project which aims to characterize almost a hundred OCs observed and analyzed in a homogeneous way.Presentamos resultados preliminares obtenidos a partir del análisis fotométrico en las bandas C y T1 del Sistema de Washington de 2 cúmulos abiertos (CAs) pobremente estudiados del cuarto cuadrante galáctico: BH 84 y BH 211. En base a los mejores ajustes de isócronas teóricas a los diagramas color-magnitud (T1, C −T1), derivamos los parámetros fundamentales de ambos objetos. Los presentes resultados constituyen parte de un proyecto mayor que prevé la caracterización de casi un centenar de CAs observados y analizados de manera homogénea.Fil: Marcionni, N.. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Parisi, M. C.. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Claria Olmedo, Juan Jose. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ahumada, Andrea Veronica. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Palma, Tali. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

Milky Way demographics with the VVV survey. IV. PSF photometry from almost one billion stars in the Galactic bulge and adjacent southern disk

Accepted for publication in a forthcoming issue of Astronomy & Astrophysics. Reproduced with permission from Astronomy & Astrophysics. © 2018 ESO.Context. The inner regions of the Galaxy are severely affected by extinction, which limits our capability to study the stellar populations present there. The Vista Variables in the Vía Láctea (VVV) ESO Public Survey has observed this zone at near-infrared wavelengths where reddening is highly diminished. Aims. By exploiting the high resolution and wide field-of-view of the VVV images we aim to produce a deep, homogeneous, and highly complete database of sources that cover the innermost regions of our Galaxy. Methods. To better deal with the high crowding in the surveyed areas, we have used point spread function (PSF)-fitting techniques to obtain a new photometry of the VVV images, in the ZY JHK s near-infrared filters available. Results. Our final catalogs contain close to one billion sources, with precise photometry in up to five near-infrared filters, and they are already being used to provide an unprecedented view of the inner Galactic stellar populations. We make these catalogs publicly available to the community. Our catalogs allow us to build the VVV giga-CMD, a series of color-magnitude diagrams of the inner regions of the Milky Way presented as supplementary videos. We provide a qualitative analysis of some representative CMDs of the inner regions of the Galaxy, and briefly mention some of the studies we have developed with this new dataset so far.Peer reviewe