Tali Palma

VISTA Variables in the Via Lactea (VVV): The public ESO near-IR variability survey of the Milky Way

Original article can be found at: http://www.sciencedirect.com/science/journal/13841076 Copyright Elsevier B.V.

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

Aims. 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 lo cated in the inner disc and outer regions of the LMC. Methods. 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 cl uster ages and metallicities from a comparison with theoretical isochrones of the Padova group. Whenever possible, we also derived ages usingδT1 - 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. Results. We find that the two methods for age and metallicity determina tion 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. Conclusions. 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 th at the younger clusters were formed closer to the LMC centre than the older ones.

FSR 1716: A New Milky Way Globular Cluster Confirmed Using VVV RR Lyrae Stars

We use deep multi-epoch near-IR images of the VISTA Variables in the Via Lactea (VVV) Survey to search for RR Lyrae stars toward the Southern Galactic plane. Here, we report the discovery of a group of RR Lyrae stars close together in VVV tile d025. Inspection of the VVV images and PSF photometry reveals that most of these stars are likely to belong to a globular cluster that matches the position of the previously known star cluster FSR 1716. The stellar density map of the field yields a >100? detection for this candidate globular cluster that is centered at equatorial coordinates R.A. J2000 = 16:10:30.0, decl. J2000 = ?53:44:56 and galactic coordinates l = 329.77812, b = ?1.59227. The color–magnitude diagram of this object reveals a well-populated red giant branch, with a prominent red clump at K s = 13.35 ± 0.05, and J ? K s = 1.30 ± 0.05. We present the cluster RR Lyrae positions, magnitudes, colors, periods, and amplitudes. The presence of RR Lyrae indicates an old globular cluster, with an age >10 Gyr. We classify this object as an Oosterhoff type I globular cluster, based on the mean period of its RR Lyrae type ab,

Near-infrared photometry and spectroscopy of the low Galactic latitude globular cluster 2MASS-GC 03

\langle P\rangle =0.540

Characterization of the VVV Survey RR Lyrae Population across the Southern Galactic Plane

days, and argue that this is a relatively metal-poor cluster with [Fe/H] = ?1.5 ± 0.4 dex. The mean extinction and reddening for this cluster are

New variable stars discovered in the fields of three Galactic open clusters using the VVV survey

{A}_{{K}_{s}}=0.38\pm 0.02

Escape of Resonantly Scattered Ly

and E(J ? K s ) = 0.72 ± 0.02 mag, respectively, as measured from the RR Lyrae colors and the near-IR color–magnitude diagram. We also measure the cluster distance using the RR Lyrae type ab stars. The cluster mean distance modulus is (m ? M)0 = 14.38 ± 0.03 mag, implying a distance D = 7.5 ± 0.2 kpc and a Galactocentric distance R G = 4.3 kpc.

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We present deep near-infrared photometry and spectroscopy of the globular cluster 2MASS-GC03 projected in the Galactic disk using MMIRS on the Clay telescope (Las Campanas Observatory) and VISTA Variables in the Via Lactea survey (VVV) data. Most probable cluster member candidates were identified from near-infrared photometry. Out of ten candidates that were followed-up spectroscopically, five have properties of cluster members, from which we calculate = -0.9 +- 0.2 and a radial velocity of v_r > = -78 +- 12km/s. A distance of 10.8kpc is estimated from 3 likely RRLyrae members. Given that the cluster is currently at a distance of 4.2kpc from the Galactic center, the clusters long survival time of an estimated 11.3 +- 1.2Gyr strengthens the case for its globular-cluster nature. The cluster has a hint of elongation in the direction of the Galactic center.

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This is an author created, un-copyedited version of an article published in The Astronomical Journal. Under embargo. Embargo end date: 27 March 2018. IOP Publishing is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at doi: https://doi.org/10.3847/1538-3881/aa5be4.

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Abstract 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 J-, H- and Ks- bands obtained from the Vista Variables in the Via Lactea (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 ( J − K s , K s ) and color-color ( H − K s , J − H ) 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, δ 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 80°. Their surface temperatures range between 3500 K and 8000 K.