3 research outputs found
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
CMDs, as well as on the 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 (
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
New variable stars discovered in the fields of three Galactic open clusters using the VVV Survey
This project is a massive near-infrared (NIR) search for variable stars in
highly reddened and obscured open cluster (OC) fields projected on regions of
the Galactic bulge and disk. The search is performed using photometric NIR data
in the -, - and - bands obtained from the Vista Variables in the
V\'ia L\'actea (VVV) Survey. We performed in each cluster field a variability
search using Stetson's variability statistics to select the variable
candidates. Later, those candidates were subjected to a frequency analysis
using the Generalized Lomb-Scargle and the Phase Dispersion Minimization
algorithms. The number of independent observations range between 63 and 73. The
newly discovered variables in this study, 157 in total in three different known
OCs, are classified based on their light curve shapes, periods, amplitudes and
their location in the corresponding color-magnitude and
color-color diagrams. We found 5 possible Cepheid stars which,
based on the period-luminosity relation, are very likely type II Cepheids
located behind the bulge. Among the newly discovered variables, there are
eclipsing binaries, Scuti, as well as background RR Lyrae stars. Using
the new version of the Wilson & Devinney code as well as the "Physics Of
Eclipsing Binaries" (PHOEBE) code, we analyzed some of the best eclipsing
binaries we discovered. Our results show that these studied systems turn out to
be ranging from detached to double-contact binaries, with low eccentricities
and high inclinations of approximately . Their surface temperatures
range between K and K.Comment: 34 pages, 10 figures, 7 tables. Accepted for publication in New
Astronom