Browsing by Author "Amigo, P."
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- ItemDisentangling multiple stellar populations in globular clusters using the Strömgren system(2015) Alonso-García, J.; Catelan, Márcio; Amigo, P.; Cortés, C.; Kuehn, C. A.; Grundahl, F.; López, G.; Salinas, R.; Smith, H. A.; Stetson, P. B.; Sweigart, Allen V.; Valcarce, Aldo A. R.; Zoccali, M.An increasing amount of spectroscopic and photometric evidence is showing that the stellar populations of globular clusters are not as simple as they have been considered for many years. The presence of at least two different populations of stars is being discovered in a growing number of globular clusters, both in our Galaxy and in others. We have started a series of observations of Galactic globular clusters using the Strömgren photometric system in order to find the signatures of these multiple populations and establish their presence in a more complete sample of globular clusters in the Milky Way, and to study their radial distributions and extensions. We present here the first results of our survey....
- ItemKinematics of a globular cluster with an extended profile: NGC 5694(2015) Bellazzini, M.; Mucciarelli, A.; Sollima, A.; Catelan, Márcio; Dalessandro, E.; Correnti, M.; D'Orazi, V.; Cortés, C .; Amigo, P.
- ItemMassive open star clusters using the VVV survey IV. WR 62-2, a new very massive star in the core of the VVV CL041 cluster(2015) Chene, A.; Ramírez, S.; Borissova, J.; O'Leary, E.; Martins, F.; Herve, A.; Kuhn, M.; Kurtev, R.; Amigo, P.; Minniti, D.; Bonatto, C.
- ItemMassive open star clusters using the VVV survey. III. A young massive cluster at the far edge of the Galactic bar(2014) Ramírez Alegría, S.; Borissova, J.; Chené, A. N.; O'Leary, E.; Amigo, P.; Minniti, D.; Saito, R. K.; Geisler, D.; Kurtev, R.; Hempel, M.; Gromadzki, M.; Clarke, J. R. A.; Negueruela, I.; Marco, A.; Fierro, C.; Bonatto, C.; Catelan, MárcioContext. Young massive clusters are key to map the Milky Way's structure, and near-infrared large area sky surveys have contributed strongly to the discovery of new obscured massive stellar clusters. Aims: We present the third article in a series of papers focused on young and massive clusters discovered in the VVV survey. This article is dedicated to the physical characterization of VVV CL086, using part of its OB-stellar population. Methods: We physically characterized the cluster using JHKS near-infrared photometry from ESO public survey VVV images, using the VVV-SkZ pipeline, and near-infrared K-band spectroscopy, following the methodology presented in the first article of the series. Results: Individual distances for two observed stars indicate that the cluster is located at the far edge of the Galactic bar. These stars, which are probable cluster members from the statistically field-star decontaminated CMD, have spectral types between O9 and B0 V. According to our analysis, this young cluster (1.0 Myr < age < 5.0 Myr) is located at a distance of 11+5-6 kpc, and we estimate a lower limit for the cluster total mass of (2.8+1.6-1.4) · 103 M⊙. It is likely that the cluster contains even earlier and more massive stars. Based on observations taken within the ESO VISTA Public Survey VVV (programme ID 179.B-2002), and with ISAAC, VLT, ESO (programme 087.D-0341A).Near-IR photometry of the most probable cluster members is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/564/L9...
- ItemMultiple populations in Galactic globular clusters from a Strömgren perspective(2014) Alonso-García, J.; Catelan, Márcio; Amigo, P.; Cortés, C.; Kuehn, C. A.; Grundahl, F.; López, G.; Salinas, R.; Smith, H. A.; Stetson, P. B.; Sweigart, Allen V.; Valcarce, Aldo A. R.; Zoccali, M.Our view of the stellar populations in globular clusters has radically changed in the last years. Now we are coming to believe that all globular clusters host at least two distinct stellar populations. We present in this contribution preliminary results of a photometric survey we are currently conducting to disentangle photometrically the several populations in a significant number of Galactic globular clusters, using the Strömgren system, aiming to characterize their relative ratios and their radial distributions....
- ItemMultiple populations in Galactic globular clusters: a survey in the Strömgren system(2013) Alonso-García, J.; Catelan, Márcio; Amigo, P.; Cortés, C.; Kuehn, C. A.; Grundahl, F.; López, G.; Salinas, R.; Smith, H. A.; Stetson, P. B.; Sweigart, Allen V.; Valcarce, Aldo A. R.; Zoccali, M.We are coming to believe that stellar populations in globular clusters are not as simple as they were once thought to be. A growing amount of photometric and spectroscopic evidence shows that globular clusters host at least two different stellar populations. In our contribution to these proceedings we present the first results of a survey we are conducting to look for the presence of multiple populations in a significant number of Galactic globular clusters, using the Strömgren system. We intend to photometrically separate these populations and characterize their radial distributions and extensions....
- ItemNew galactic star clusters discovered in the VVV survey. Candidates projected on the inner disk and bulge(2014) Borissova, J.; Chene, A.; Ramirez Alegria, S.; Sharma, S.; Clarke, J.; Kurtev, R.; Negueruela, I.; Minniti, D.; Catelan, Márcio; Hempel, Maren; Marco, A.; Amigo, P.
- ItemNGC 5694: another extra-galactic globular cluster(2013) Mucciarelli, A.; Bellazzini, M.; Catelan, Márcio; Amigo, P.; Correnti, M.; Cortés, C.; Dalessandro, E.; D'Orazi, V.We discuss the chemical composition of six giant stars of the outer Halo globular cluster NGC 5694, through the analysis of UVES@FLAMES high-resolution spectra. The cluster has an average iron content [Fe/H]=-1.83±0.01, solar-scaled [alpha /Fe] ratios and a very low Ba abundance ([Ba/Fe]=-0.71±0.06). These anomalous abundance patterns are different from those observed in other Halo globular clusters but similar to those of the metal-poor stars in typical dwarf spheroidal galaxies. These findings suggest an extra-galactic origin for NGC 5694, likely from a dwarf spheroidal galaxy....
- ItemStellar variability in the VVV survey(2013) Catelan, Márcio; Minniti, D.; Lucas, P. W.; Dékány, I.; Saito, R. K.; Angeloni, Rodolfo; Alonso-García, J.; Hempel, M.; Helminiak, Krzysztof Grzegorz; Jordán, A.; Contreras Ramos, Rodrigo Andrés; Navarrete, C.; Beamin Muhlenbrock, Juan Carlos; Rojas, A. F.; Gran, F.; Ferreira Lopes, C. E.; Contreras Peña, Carlos Eduardo; Kerins, E.; Huckvale, L.; Rejkuba, M.; Cohen, R.; Mauro, F.; Borissova, J.; Amigo, P.; Eyheramendy Duerr, Susana; Pichara Baksai, Karim Elías; Espinoza, N.; Navarro, C.; Hajdu, G.; Calderón Espinoza, Diego Nicolás; Muro, G. A.; Andrews, H.; Motta, V.; Kurtev, R.; Emerson, J. P.; Moni Bidin, C.; Chené, A. -N.The Vista Variables in the Via Lactea (VVV) ESO Public Survey is an ongoing time-series, near-infrared (IR) survey of the Galactic bulge and an adjacent portion of the inner disk, covering 562 square degrees of the sky, using ESOs VISTA telescope. The survey has provided superb multi-color photometry in 5 broadband filters ($Z$, $Y$, $J$, $H$, and $K_s$), leading to the best map of the inner Milky Way ever obtained, particularly in the near-IR. The main variability part of the survey, which is focused on $K_s$-band observations, is currently underway, with bulge fields having been observed between 31 and 70 times, and disk fields between 17 and 36 times. When the survey is complete, bulge (disk) fields will have been observed up to a total of 100 (60) times, providing unprecedented depth and time coverage. Here we provide a first overview of stellar variability in the VVV data, including examples of the light curves that have been collected thus far, scientific applications, and our efforts towards the automated classification of VVV light curves....
- ItemStellar variability in the VVV survey: overview and first results(2013) Catelan, Márcio; Minniti, D.; Lucas, P. W.; Dékány, I.; Saito, R. K.; Angeloni, Rodolfo; Alonso-García, J.; Hempel, M.; Hełminiak, K.; Jordán, A.; Contreras Ramos, Rodrigo Andrés; Navarrete, C.; Beamin Muhlenbrock, Juan Carlos; Rojas, A. F.; Gran, F.; Ferreira Lopes, C. E.; Contreras Peña, Carlos Eduardo; Kerins, E.; Huckvale, L.; Rejkuba, M.; Cohen, R.; Mauro, F.; Borissova, J.; Amigo, P.; Eyheramendy Duerr, Susana; Pichara Baksai, Karim Elías; Espinoza, N.; Navarro, C.; Hajdu, G.; Calderón Espinoza, Diego Nicolás; Muro, G. A.; Andrews, H.; Motta, V.; Kurtev, R.; Emerson, J. P.; Moni Bidin, C.; Chené, A. -N.The Vista Variables in the Vía Láctea (VVV) ESO Public Survey is an ongoing time-series, near-infrared (IR) survey of the Galactic bulge and an adjacent portion of the inner disk, covering 562 square degrees of the sky, using ESOs VISTA telescope. The survey has provided superb multi-color photometry in 5 broadband filters (Z, Y, J, H, and K<SUB>s</SUB> ), leading to the best map of the inner Milky Way ever obtained, particularly in the near-IR. The main part of the survey, which is focused on the variability in the K<SUB>s</SUB> -band, is currently underway, with bulge fields observed between 34 and 73 times, and disk fields between 34 and 36 times. When the survey is complete, bulge (disk) fields will have been observed up to a total of 100 (60) times, providing unprecedented depth and time coverage in the near-IR. Here we provide a first overview of stellar variability in the VVV data....
- ItemTheoretical modeling of the RR Lyrae variables in NGC 1851(2015) Kunder, A.; Salaris, M.; Cassisi, S.; de Propris, R.; Walker, A.; Stetson, P. B.; Catelan, Marcio; Amigo, P.The RR Lyrae instability strip (IS) in NGC 1851 is investigated, and a model is presented which reproduces the pulsational properties of the RR Lyrae population. In our model, a stellar component within the IS that displays minor helium variations (Y∼0.248-0.270) is able to reproduce the observed periods and amplitudes of the RR Lyrae variables, as well as the frequency of fundamental and first-overtone RR Lyrae variables. The RR Lyrae variables therefore may belong to an He-enriched second generation of stars. The RR Lyrae variables with a slightly enhanced helium (Y∼0.270-0.280) have longer periods at a given amplitude, as is seen with Oosterhoff II (OoII) RR Lyrae variables, whereas the RR Lyrae variables with Y∼0.248-0.270 have shorter periods, exhibiting properties of Oosterhoff I (OoI) variables. %.
- ItemTime-series BVi photometry for the globular cluster NGC 6981(2013) Amigo, P.; Stetson, P.; Catelan, Márcio; Zoccali, Manuela; Smith, H.
- ItemYOUNG. STELLAR. CLUSTERS. CONTAINING. MASSIVE. YOUNG. STELLAR. OBJECTS. IN. THE. VVV. SURVEY(2016) Borissova, J.; Ramírez Alegría, S.; Alonso, J.; Lucas, P. W.; Kurtev, R.|Medina, N.; Navarro, C.|Kuhn, M.; Gromadzki, M.; Catelan, Márcio; Retamales, G.; Fernández, M. A.; Agurto-Gangas, C.; Chené, A. N.; Minniti, D.; Contreras Peña, Carlos Eduardo; Decany, I.; Thompson, M. A.; Morales, E. F. E.; Amigo, P.