Browsing by Author "Torrealba, Gabriel"
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- ItemDiscovery of 30,000 Periodic Variables in the Southern Sky(2016) Drake, Andrew J.; Djorgovski, Stanislav G.; Graham, Matthew; Catelan, Márcio; Torrealba, Gabriel; Mahabal, Ashish A.; Christensen, Eric J.; Larson, Stephen M.; McNaught, Robert; Garradd, GordonWe have completed a search for periodic variable stars within the 30,000 square degrees of the sky covered by the Catalina Surveys. Here we present the results from our analysis of six years of optical photometry taken by the Siding Spring Survey (SSS). This data covers 200 million sources at declinations between -20 and -75 degrees in the magnitude range 11 < V < 19. In addition to the 10,000 RR Lyrae that we previously discovered in this data, we find approximately 30,000 new periodic variable stars. These sources include, eclipsing binaries, RR Lyrae, LPVs, RSCVn stars, delta Scutis and Anomalous Cepheids.As part of our ongoing search for structure within the Galactic halo we determine the distances to each of the type-ab RR Lyrae. We discover that many of these stars appear to belong to the old stellar halo of the LMC. Our analysis suggests that the stellar halo of the LMC extends far beyond the limits previously observed....
- ItemPeriodic Variable Stars Across the Southern Sky(2015) Drake, Andrew J.; Graham, Matthew; Djorgovski, Stanislav G.; Catelan, Márcio; Torrealba, Gabriel; Mahabal, Ashish A.; Donalek, Ciro; Christensen, Eric J.; Larson, Stephen M.; McNaught, Robert; Garradd, GordonWe continue our search for periodic variables within the ~30,000 square degrees of the sky covered by the Catalina Surveys. Here we analyze six years of optical photometry taken by the Siding Spring Survey (SSS), which is sensitive to sources in the range 11 < V < 19. In all, this new analysis covers ten thousand square degrees on the sky at declinations between -20 and -75 degrees. Due to the very large number of periodic variable candidates found, we perform automated classification of the stars using multivariate kernel density estimation based on features selected from previously classified northern data. We test the accuracy of the results by visually validating a large sample of the objects. We also compare the classifications with those from other automated methods. The final SSS catalog contains tens of thousands of new periodic variable stars including eclipsing binaries, RR Lyrae, LPVs, delta Scuti's and Cepheids. By combining the newly discovered LPVs and RR Lyrae with our previous discoveries, we trace the path of the Sagittarius tidal streams system across the entire sky....
- ItemSearching for the Progenitor Galaxy of Omega Centauri Using RR Lyrae Spectra(2017) Carignano, Natalia; Vivas, Anna Katherina; Catelan, Marcio; Torrealba, Gabriel; Fernandez Trincado, Jose GregorioRadial velocities of 32 RR Lyrae stars from the Catalina Real-time Transient Survey in the neighborhood of Omega Centauri were measured from low-resolution spectra taken by the Goodman Spectrograph on SOAR, Cerro Pachón, Chile. An over-density of stars with the same velocity as the cluster would imply that these stars were once part of ω Cen but have since been tidally stripped, supporting the hypothesis that ω Cen is the remain of a nucleated dwarf galaxy. This study is the most complete of any one similar, covering an area of 100 sq. degrees around the cluster and using RR Lyrae stars known to have similar distance to the cluster. Statistical tests comparing the distribution of RR Lyrae velocities to the expected distribution of velocities of halo stars show no over-density of stars at the velocity of ω Cen or any other velocity, discarding the presence of any substructure in this part of the sky....