Browsing by Author "Amigo, Pía"
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- ItemNew Variable Stars in CMa Globular Cluster Candidates(2011) Amigo, Pía; Catelan, Márcio; Stetson, Peter B.; Smith, Horace A.; Cacciari, Carla; Zoccali, ManuelaWe present the preliminary results of an image-subtraction analysis of the Galactic globular cluster M79 (NGC 1904), as well as a new investigation of the variable star population in NGC 1851. Both M79 and NGC 1851 have been previously associated with the Canis Major overdensity, which has been suggested to have an extragalactic origin. We found 6 new RR Lyrae in M79, and also recovered 3 previously known RR Lyrae. The average period of the 5 ab-type RR Lyrae is 0.68 d, corresponding to an Oosterhoff II classification -- which is unusual, though not unprecedented, for systems of extragalactic origin. We also report on the discovery of at least 4 previously unknown variables in NGC 1851....
- ItemRelative ratios and radial distributions of the multiple populations in the Galactic globular clusters(2015) Alonso-Garcia, Javier; Catelan, Marcio; Amigo, Pía; Contreras Ramos, Rodrigo; Cortés, Cristián; Kuehn, Charles; Grundahl, Frank; López, Graciela; Salinas, Ricardo; Smith, Horace; Stetson, Peter; Sweigart, Allen; Valcarce, Aldo A. R.; Zoccali, ManuelaRecently, the long-standing paradigm that globular clusters are close approximations to simple stellar populations, with all stars formed at precisely the same time from populations having precisely the same chemical composition, has been shattered by a series of photometric and spectroscopic observations that reveal that these objects are more complex than we once thought . In this poster, we present the first results of a survey we are conducting among the Galactic globular clusters using the Strömgren photometric system. We show that the bluest Strömgren filters reveal broadenings or splits in the stellar sequences in the color-magnitude diagrams of the sampled clusters. These features allow us to disentangle successfully the different stellar populations in a given globular cluster, which let us measure their relative ratios, and explore their radial trends and gradients from the cluster center out to its tidal radius....
- ItemRR Lyrae Variables in NGC 2808(2011) Kunder, Andrea; Stetson, Peter B.; Catelan, Marcio; Amigo, Pía; de Propris, RobertoNGC 2808 is a unique globular cluster with not only a bimodal-horizontal branch (HB) but also with gaps on the blue horizontal branch. Adequate interpretation of the nature of the detected peculiarities in "bimodal" and "gap" clusters is of paramount importance for understanding the nature of the second parameter phenomenon and scenarios for the formation of the Galaxy. Although RR Lyrae variables are HB stars that can provide powerful constraints to models on the origin of bimodal HBs, unfortunately, until recently, only one RR Lyrae variable was known in this cluster. Here we present the first calibrated time-series CCD photometry for newly discovered fundamental mode RR Lyrae variables in NGC 2808, with observations over a range of twenty years. Investigations of RR Lyrae variable stars in this peculiar, bimodal-horizontal branch globular cluster are carried out to account for its formation, and the effects of helium enrichment and differential reddening. The Oosterhoff classification of NGC 2808, which has recently been associated with a previously unknown dwarf galaxy in Canis Major, is also discussed....
- ItemVariable stars in the VVV globular clusters. I. 2MASS-GC 02 and Terzan 10(2015) Alonso García, Javier; Dékány, István; Catelan, Márcio; Gran, Felipe; Amigo, Pía; Leyton, Paul; Minniti, D.