Browsing by Author "Alonso-Garcia, Javier"
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- ItemConfirmation of a New Metal-poor Globular Cluster in the Galactic Bulge(2018) Minniti, D.; Schlafly, E. F.; Palma, Tali; Claria, Juan J.; Hempel, Maren; Alonso-Garcia, Javier; Bica, Eduardo; Bonatto, Charles; Braga, Vittorio F.; Clementini, Gisella; Garofalo, Alessia; Gomez, Matias; Ivanov, Valentin D.; Lucas, Phill
- ItemDeep Hubble Space Telescope Imaging of Globular Clusters toward the Galactic Bulge: Observations, Data Reduction, and Color-magnitude Diagrams(2018) Cohen, Roger E.; Mauro, Francesco; Alonso-Garcia, Javier; Hempel, Maren; Sarajedini, Ata; Ordonez, Antonio J.; Geisler, Douglas; Kalirai, Jason S.
- ItemDiscovery of Tidal RR Lyrae Stars in the Bulge Globular Cluster M62(2018) Minniti, D.; Fernandez-Trincado, Jose G.; Ripepi, Vincenzo; Alonso-Garcia, Javier; Contreras Ramos, Rodrigo Andrés; Marconi, Marcella
- ItemMilky Way demographics with the VVV survey IV. PSF photometry from almost one billion stars in the Galactic bulge and adjacent southern disk(2018) Alonso-Garcia, Javier; Saito, Roberto K.; Hempel, Maren; Minniti, D.; Pullen, Joyce; Catelan, Márcio; Contreras Ramos, Rodrigo Andrés; Cross, Nicholas J.G.; Gonzalez, Oscar A.; Zoccali, Manuela; Lucas, Philip W.; Palma, Tali; Valenti, Elena
- 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....
- ItemStellar Variability in the VVV Survey: Highlights and Current Status(2015) Catelan, Marcio; Dékány, István; Minniti, Dante; Alonso-Garcia, Javier; Contreras Ramos, Rodrigo; Saito, Roberto; Hajdu, Gergely; Lucas, Phil; Kerins, Eamonn; Hempel, MarenThe Vista Variables in the Via Lactea (VVV) ESO Public Survey consists in a near-infrared time-series survey of the Galactic bulge and inner disk, covering 562 square degrees of the sky, over a total timespan of more than 5 years. In this contribution, we discuss some of our latest results, and provide an updated account of the current status of the survey, especially in the context of stellar variability studies....
- ItemThe most variable VVV sources: eruptive protostars, dipping giants in the Nuclear Disc and others(2023) Lucas, Phil; Smith, Leigh; Guo, Zhen; Contreras Peña, Carlos; Minniti, Dante; Miller, Niall; Alonso-Garcia, Javier; Catelan, Marcio; Borissova, J.; Saito, Roberto; Kurtev, Radostin; Navarro, M. G.; Morris, Calum; Muthu, Hariharan; Froebrich, Dirk; Ivanov, Valentin; Bayo, Amelia; Caratti, Alessio; Sanders, JasonWe have performed a comprehensive search of a VISTA Variables in the Via Lactea (VVV) data base of 9.5 yr light curves for variable sources with ΔKs ≥ 4 mag, aiming to provide a large sample of high amplitude eruptive young stellar objects (YSOs) and detect unusual or new types of infrared variable source. We find 222 variable or transient sources in the Galactic bulge and disc, most of which are new discoveries. The sample mainly comprises novae, YSOs, microlensing events, Long Period Variable stars (LPVs), and a few rare or unclassified sources. Additionally, we report the discovery of a significant population of aperiodic late-type giant stars suffering deep extinction events, strongly clustered in the Nuclear Disc of the Milky Way. We suggest that these are metal-rich stars in which radiatively driven mass loss has been enhanced by super-solar metallicity. Among the YSOs, 32/40 appear to be undergoing episodic accretion. Long-lasting YSO eruptions have a typical rise time of ∼2 yr, somewhat slower than the 6–12 month time-scale seen in the few historical events observed on the rise. The outburst durations are usually at least 5 yr, somewhat longer than many lower amplitude VVV events detected previously. The light curves are diverse in nature, suggesting that multiple types of disc instability may occur. Eight long-duration extinction events are seen wherein the YSO dims for a year or more, attributable to inner disc structure. One binary YSO in NGC 6530 displays periodic extinction events (P=59 d) similar to KH 15D.
- ItemThe structure behind the galactic bar traced by red clump stars in the VVV survey(2018) Gonzalez, Oscar A.; Minniti, D.; Valenti, Elena; Alonso-Garcia, Javier; Debattista, Victor P.; Zoccali, Manuela; Rejkuba, Marina; Dias, Bruno; Surot, Bruno; Hempel, Maren
- ItemThe VVV Survey RR Lyrae Population in the Galactic Center Region(2018) Contreras Ramos, Rodrigo Andrés; Minniti, D.; Gran, Felipe; Zoccali, Manuela; Alonso-Garcia, Javier; Huijse, Pablo; Gabriela Navarro, Maria; Rojas-Arriagada, Alvaro; Valenti, Elena
- ItemVariable Stars in VVV Globular Clusters(2015) Contreras Ramos, Rodrigo; Alonso-Garcia, Javier; Minniti, Dante; Catelan, Márcio; Zoccali, Manuela; Gran, Felipe; Dekany, IstvanThe Vista Variables in the Via Lactea (VVV) is an ongoing variability survey observing the central regions of our Galaxy in the near-infrared by means of the VISTA telescope. Numerous (36) inner Galactic globular clusters fall inside the area covered by the VVV survey. Most of these clusters, especially the faintest ones, have been poorly studied in the past due to the difficulties caused by the presence of an elevated extinction and high field stellar densities in their lines of sight. We will present the first results of a search for variable stars we are conducting in some of these clusters. Our main aim is to obtain a better determination of the physical parameters of these globular clusters and put constrains on the formation scenario of our galaxy using the information provided by their variables stars.