DSpace Angular :: Browsing by Author "Dékány, I."

Browsing by Author "Dékány, I."

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Bulge RR Lyrae stars in the VVV tile b201
(2015) Gran, F.; Minniti, D.; Saito, R. K.; Navarrete, C.; Dékány, I.; McDonald, I.; Contreras Ramos, Rodrigo Andrés; Catelan, Márcio
Establishing the galactic centre distance using VVV bulge RR lyrae variables
(2018) Majaess, D.; Dékány, I.; Hajdu, Gergely; Minniti, D.; Turner, D.; Gieren Waiblinger, Wolfgang Paul
Main and Early Shocks in RR Lyrae Photometric Light Curves
(2021) Prudil, Z.; Smolec, R.; Catelan, Márcio; Dékány, I.; Grebel, E. K.; Kunder, A.
We explore the effect of the main and early shocks (giving rise to the so-called hump and bump features in the light curves, respectively) on the pulsation properties of non-modulated fundamental mode RR Lyrae stars. We utilized I-band photometry from the fourth release of the Optical Gravitational Lensing Experiment (OGLE). We determined the centers and strengths of humps and bumps in the phased light curves of the studied stars. The positions of both shock events in the phased light curves are highly correlated with the amplitudes, pulsation periods, and Fourier coefficients. RR Lyrae stars with prominent humps are located at the low-amplitude regime of the Bailey diagram, while variables with pronounced bumps have average and above average amplitudes. RR Lyrae stars close to the red edge of the instability strip have pronounced humps, while variables with a strong bump are located at the center and close to the blue edge of the instability strip. In general, the effect of the main and early shocks provides a new view on the period-amplitude distribution of fundamental mode RR Lyrae stars....
Near-IR period-luminosity relations for pulsating stars in ω Centauri (NGC 5139) (Corrigendum)
(2017) Navarrete, C.; Catelan, Márcio; Contreras Ramos, Rodrigo; Alonso-García, J.; Gran, F.; Dékány, I.; Minniti, D.
Erratum for: "An incorrect zero point for the empirical period-luminosity-metallicity (PL-Z) relations for RR Lyrae (RRL) stars in ω Centauri (NGC 5139) was inadvertently reported in Table 2 and Eqs. (4) and (5) of our original paper. The corrected table and equations are given below. The actual analysis that is described in the paper was based on the correct zero points, and so all of the results reported in our original publication remain unchanged".
Optical/Near-Infrared Light-Curve Properties of Pulsating Variables in the Cepheid Instability Strip
(2014) Calderón Espinoza, Diego Nicolás; Hajdu, Gergely; Dékány, I.; Catelan, Márcio
Making the distinction between Type I and II Cepheids found in the Vista Variables in the Via Lactea (VVV) ESO Public Survey is crucial for the studies of Galactic structure using these variables. As VVV provides only K_{S}-band light curves, this distinction has to be based on near-IR light-curve properties. Because of their reduced amplitudes in the near-IR, however, it is not immediately obvious whether such a distinction can be unambiguously made. To assess this problem, we have compared the VVV and VVV Templates K_{S}-band light-curve properties of 213 Type I and 215 Type II Cepheids using Fourier decomposition. The Fourier parameters of these types were found to be different enough for the purposes of classification. For example, over most of the Cepheid period range, there is an upper limit for the amplitudes of Type I Cepheids. As 50 percent of the Type II variables lie above this limit, half of the variables that could be confused with Type I Cepheids are sorted out by this simple feature alone, suggesting that the automatic classification schemes under development for the VVV Survey will be able to classify such variables with a high degree of accuracy. We have also found that bump Cepheids can be easily identified using VVV data, as the bump feature also appears in the near-IR light curves. Detailed modeling of the light curves of the bump Cepheids found in the VVV data will provide accurate stellar parameters for these stars....
Searches for variability in the Milky Way bulge with the VVV Survey
(2014) Saito, R. K.; Minniti, D.; Catelan, Marcio; Gran, F.; Iglesias, D.; Muro, G.; Beamin, J. C.; Dékány, I.
VVV is an ongoing near-IR, multi-band, time-series survey of the Galactic bulge and plane. Here we summarize the first results from a search for variability in selected fields of the VVV bulge area....
Searching for Variable Stars in the VVV Globular Clusters
(2015) Alonso-García, J.; Dékány, I.; Catelan, Marcio; Contreras, R.; Minniti, D.
The “VISTA Variables in the Vía Láctea” (VVV) ESO Public Survey data is currently surveying the central regions of the Milky Way at near-infrared wavelengths, including 36 known Galactic globular clusters. We already have data in several filters to generate their color-magnitude diagrams. We also have enough epochs to begin producing the light curves of the cluster stars and look for any possible member variable stars. We are especially interested in RR Lyrae stars, since they are abundant in Galactic globular clusters and the period-luminosity relation they show at near-infrared wavelengths can help enormously in providing accurate distances and reddenings for the most extincted and poorly studied inner Galactic globular clusters. We center our attention here in the preliminary analysis of three of these clusters: NGC 6441, Terzan 10 and 2MASS-GC02....
Spatial and Kinematical Study of the Oosterhoff Dichotomy in the Galactic Bulge
(2020) Prudil, Z.; Dékány, I.; Catelan, Marcio; Grebel, E. K.; Smolec, R.; Skarka, M.
We present results of spatial and kinematical studies on the Oosterhoff dichotomy in the Galactic bulge based on data from the fourth data release of the Optical Gravitational Lensing Experiment (OGLE). The Oosterhoff groups I and II were separated by conventional augmenting techniques as well as by using a dimensionality reduction machine learning algorithm accompanied by a clustering algorithm. We find, as also seen in globular clusters, that the Oosterhoff II RR Lyrae stars are on the average cooler, more metal-poor, and more massive than RR Lyrae variables associated with the Oosterhoff I group. In addition, neither group seems to be spatially associated with the Galactic bar. For a fraction of our sample, we were able to obtain a 6D kinematical solution, and for these stars, the two Oosterhoff groups do not show a systematic difference in their space velocity distribution. Based on their orbits we estimate that 8 % of the bulge RR Lyrae stars are halo interlopers, and the majority of the studied stars are well confined within the Galactic bulge....
The general catalog of VISTA variables in the Via Lactea
(2014) Dékány, I.; Pullen, J.; Minniti, D.; Catelan, Marcio
The VISTA Variables in the Via Lactea (VVV) ESO Public Survey is providing deep, long-baseline time-series photometry in the near-infrared for hundreds of millions of objects in the bulge and the southern disk. The scientific potential of these data is manifold, and its global exploration requires homogeneous and high-level data products. In my talk, I will expound on the details of a massive computational effort to produce a general variability database and a catalog of periodic and transient variables in the bulge, using photometry provided by the VISTA Data Flow System. The goal of this project is to duly provide science-ready data products in the form of a simple on-line database which may serve as the basis for various specific studies from stellar pulsation to microlensing, conducted by the VVV community. I will discuss the main steps of the procedure, the characteristics and possible uses of the database, the current status of the project, and will conclude by highlighting selected results....
The VVV Survey of the Milky Way: first year results
(2011) Minniti, D.; Clariá, J. J.; Saito, R. K.; Hempel, M.; Lucas, P. W.; Rejkuba, M.; Toledo, I.; Gonzalez, O. A.; Alonso-García, J.; Irwin, M. J.; Gonzalez-Solares, E.; Cross, N.; Ivanov, V. D.; Soto, M.; Dékány, I.; Angeloni, R.; Catelan, Marcio; Amôres, E. B.; Gurovich, S.; Emerson, J. P.; Lewis, J.; Hodgkin, S.; Pietrukowicz, P.; Zoccali, M.; Sale, S. E.; Barbá, R.; Barbuy, B.; Beamin, J. C.; Helminiak, K.; Borissova, J.; Folkes, S. L.; Gamen, R. C.; Geisler, D.; Mauro, F.; Chené, A. -N.; Alonso, M. V.; Gunthardt, G.; Hanson, M.; Kerins, E.; Kurtev, R.; Majaess, D.; Martín, E.; Masetti, N.; Mirabel, I. F.; Monaco, L.; Moni Bidin, C.; Padilla, N.; Rojas, A.; Pietrzynski, G.; Saviane, I.; Valenti, E.; Weidmann, W.; López-Corredoira, M.; Ahumada, A. V.; Aigrain, S.; Arias, J. I.; Bica, E.; Bandyopadhyay, R. M.; Baume, G.; Bedin, L. R.; Bonatto, C.; Bronfman, L.; Carraro, G.; Contreras, C.; Davis, C. J.; de Grijs, R.; Dias, B.; Drew, J. E.; Fariña, C.; Feinstein, C.; Fernández Lajús, E.; Gieren, W.; Goldman, B.; Gosling, A.; Hambly, N. C.; Hoare, M.; Jordán, A.; Kinemuchi, K.; Maccarone, T.; Merlo, D. C.; Mennickent, R. E.; Morelli, L.; Motta, V.; Palma, T.; Popescu, B.; Parisi, M. C.; Parker, Q.; Pignata, G.; Read, M. A.; Ruiz, M. T.; Roman-Lopes, A.; Schreiber, M. R.; Schröder, A. C.; Smith, M.; Sodré, L., Jr.; Stephens, A. W.; Walton, N. A.; Zijlstra, A. A.; Tamura, M.; Tappert, C.; Thompson, M. A.; Vanzi, L.
The VISTA Variables in the Via Lactea (VVV) is an ESO public near-IR variability survey that is scanning the Milky Way bulge and an adjacent section of the Galactic mid-plane. The survey will take 1929 hours of observations with the VISTA 4.1-m telescope during five years, covering a billion point sources across an area of 520 sqdeg, including 36 known globular clusters and more than 350 open clusters. The final product will be a deep IR atlas in five passbands (0.9 - 2.5 microns) and a catalogue of more than a million variable point sources....
The VVV Survey: New Results (Part I)
(2014) Minniti, D.; Saito, R. K.; Hempel, M.; Lucas, P. W.; Rejkuba, M.; Toledo, I.; Gonzalez, O. A.; Alonso-García, J.; Irwin, M. J.; Gonzalez-Solares, E.; Hodgkin, S. T.; Lewis, J. R.; Cross, N.; Ivanov, V. D.; Kerins, E.; Emerson, J. P.; Soto, M.; Amôres, E. B.; Gurovich, S.; Dékány, I.; Angeloni, R.; Beamin, J. C.; Catelan, Marcio; Padilla, N.; Zoccali, M.; Pietrukowicz, P.; Moni Bidin, C.; Mauro, F.; Geisler, D.; Folkes, S. L.; Sale, S. E.; Borissova, J.; Kurtev, R.; Ahumada, A. V.; Alonso, M. V.; Adamson, A.; Arias, J. I.; Bandyopadhyay, R. M.; Barbá, R. H.; Barbuy, B.; Baume, G. L.; Bedin, L. R.; Benjamin, R.; Bica, E.; Bonatto, C.; Bronfman, L.; Carraro, G.; Chenè, A. N.; Clariá, J. J.; Clarke, J. R. A.; Contreras, C.; Corvillón, A.; de Grijs, R.; Dias, B.; Drew, J. E.; Fariía, C.; Feinstein, C.; Fernández-Lajús, E.; Gamen, R. C.; Gieren, W.; Goldman, B.; González-Fernández, C.; Grand, R. J. J.; Gunthardt, G.; Hambly, N. C.; Hanson, M. M.; Helminiak, K.; Hoare, M. G.; Huckvale, L.; Jordán, A.; Kinemuchi, K.; Longmore, A.; López-Corredoira, M.; Maccarone, T.; Majaess, D.; Martín, E.; Masetti, N.; Mennickent, R. E.; Mirabel, I. F.; Monaco, L.; Morelli, L.; Motta, V.; Palma, T.; Parisi, M. C.; Parker, Q.; Peñaloza, F.; Pietrzyński, G.; Pignata, G.; Popescu, B.; Read, M. A.; Rojas, A.; Roman-Lopes, A.; Ruiz, M. T.; Saviane, I.; Schreiber, M. R.; Schröder, A. C.; Sharma, S.; Smith, M. D.; Sodré, L.; Stead, J.; Stephens, A. W.; Tamura, M.; Tappert, C.; Thompson, M. A.; Valenti, E.; Vanzi, L.; Walton, N. A.; Weidmann, W.; Zijlstra, A.
The VVV Survey: New Results (Part II)
(2014) Minniti, D.; Saito, R. K.; Hempel, M.; Lucas, P. W.; Rejkuba, M.; Toledo, I.; Gonzalez, O. A.; Alonso-García, J.; Irwin, M. J.; Gonzalez-Solares, E.; Hodgkin, S. T.; Lewis, J. R.; Cross, N.; Ivanov, V. D.; Kerins, E.; Emerson, J. P.; Soto, M.; Amôres, E. B.; Gurovich, S.; Dékány, I.; Angeloni, R.; Beamin, J. C.; Catelan, Marcio; Padilla, N.; Zoccali, M.; Pietrukowicz, P.; Moni Bidin, C.; Mauro, F.; Geisler, D.; Folkes, S. L.; Sale, S. E.; Borissova, J.; Kurtev, R.; Ahumada, A. V.; Alonso, M. V.; Adamson, A.; Arias, J. I.; Bandyopadhyay, R. M.; Barbá, R. H.; Barbuy, B.; Baume, G. L.; Bedin, L. R.; Benjamin, R.; Bica, E.; Bonatto, C.; Bronfman, L.; Carraro, G.; Chenè, A. N.; Clariá, J. J.; Clarke, J. R. A.; Contreras, C.; Corvillón, A.; de Grijs, R.; Dias, B.; Drew, J. E.; Fariña, C.; Feinstein, C.; Fernández-Lajús, E.; Gamen, R. C.; Gieren, W.; Goldman, B.; González-Fernández, C.; Grand, R. J. J.; Gunthardt, G.; Hambly, N. C.; Hanson, M. M.; Helminiak, K.; Hoare, M. G.; Huckvale, L.; Jordán, A.; Kinemuchi, K.; Longmore, A.; López-Corredoira, M.; Maccarone, T.; Majaess, D.; Martín, E.; Masetti, N.; Mennickent, R. E.; Mirabel, I. F.; Monaco, L.; Morelli, L.; Motta, V.; Palma, T.; Parisi, M. C.; Parker, Q.; Peñaloza, F.; Pietrzyński, G.; Pignata, G.; Popescu, B.; Read, M. A.; Rojas, A.; Roman-Lopes, A.; Ruiz, M. T.; Saviane, I.; Schreiber, M. R.; Schröder, A. C.; Sharma, S.; Smith, M. D.; Sodré, L.; Stead, J.; Stephens, A. W.; Tamura, M.; Tappert, C.; Thompson, M. A.; Valenti, E.; Vanzi, L.; Walton, N. A.; Weidmann, W.; Zijlstra, A.
The VVV Templates Project
(2014) Contreras Ramos, R.; Catelan, Marcio; Gran, F.; Navarrete, C.; Angeloni, R.; Alonso-García, J.; Dékány, I.; Hajdu, G.; Hempel, M.; Jordán, A.; Townsend, B.; Borissova, J.; Navarro, C.; Pichara, K.; Eyheramendy, S.
Until now, stellar variability in the near-IR has been a relatively ill-explored research field. In particular, the number of high-quality light curves is very limited and, even worse, many variability classes have not yet been observed in a sufficiently extensive way in the near-IR, so that good light curves are entirely lacking for some such classes. Since VVV is the first ever large survey dedicated to stellar variability in the near-infrared, the first problem we had to face has thus been the construction of a proper statistically significant database of high-quality (i.e., template) near-IR light curves for a significant sample of stars taken to be representative of the different variability classes under study. The main purpose of the VVV Templates Project is thus to build a large database of well-defined, high-quality, near-IR light curves for variable stars of different types, which will form the basis of the VVV automated classification algorithms...
The VVV Templates Project Towards Automated Classification of VVV Light Curves
(2011) Catelan, Marcio; Angeloni, R.; Dékány, I.; Pichara, K.; Eyheramendy, S.; Borissova, J.
The main goal of the VVV Templates Project is to build a large database of well-defined, high-quality near-IR light curves for variable stars of different types, which will form the basis of the VVV automated classification algorithms.
The WFCAM multiwavelength Variable Star Catalog (Corrigendum)
(2015) Ferreira Lopes, C. E.; Dékány, I.; Catelan, Marcio; Cross, N. J. G.; Angeloni, R.; Leão, I. C.; De Medeiros, J. R.
Variability Survey of ω Centauri in the Near-IR: Period-Luminosity Relations
(2017) Navarrete, C.; Catelan, Marcio; Contreras Ramos, R.; Gran, F.; Alonso-García, J.; Dékány, I.
ω Centauri is by far the most massive globular star cluster in the Milky Way, and possibly the remnant of a dwarf galaxy. As such, it contains a large number of variable stars of different classes. Here we report on an extensive, wide-field time-series study of ω Cen in the J and K S bands, which has allowed us to study the near-IR period-luminosity relations for different variability classes, including the first such relations for the SX Phoenicis stars.
VISTA Variables in the Via Lactea (VVV): Current Status and First Results
(2010) Saito, R.; Hempel, M.; Alonso-García, J.; Toledo, I.; Borissova, J.; González, O.; Beamin, J. C.; Minniti, D.; Lucas, P.; Emerson, J.; Ahumada, A.; Aigrain, S.; Alonso, M. V.; Amôres, E.; Angeloni, R.; Arias, J.; Bandyopadhyay, R.; Barbá, R.; Barbuy, B.; Baume, G.; Bedin, L.; Bica, E.; Bronfman, L.; Carraro, G.; Catelan, Marcio; Clariá, J.; Contreras, C.; Cross, N.; Davis, C.; de Grijs, R.; Dékány, I.; Janet Drew, J. D.; Fariña, C.; Feinstein, C.; Fernández Lajús, E.; Folkes, S.; Gamen, R.; Geisler, D.; Gieren, W.; Goldman, B.; Gosling, A.; Gunthardt, G.; Gurovich, S.; Hambly, N.; Hanson, M.; Hoare, M.; Irwin, M.; Ivanov, V.; Jordán, A.; Kerins, E.; Kinemuchi, K.; Kurtev, R.; Longmore, A.; López-Corredoira, M.; Maccarone, T.; Martín, E.; Masetti, N.; Mennickent, R.; Merlo, D.; Messineo, M.; Mirabel, F.; Monaco, L.; Moni Bidin, C.; Morelli, L.; Padilla, N.; Palma, T.; Parisi, M. C.; Parker, Q.; Pavani, D.; Pietrukowicz, P.; Pietrzynski, G.; Pignata, G.; Rejkuba, M.; Rojas, A.; Roman Lopes, A.; Ruiz, M. T.; Sale, S.; Saviane, I.; Schreiber, M.; Schröder, A.; Sharma, S.; Smith, M.; Sodré, L., Jr.; Soto, M.; Stephens, A.; Tamura, M.; Tappert, C.; Thompson, M.; Valenti, E.; Vanzi, L.; Weidmann, W.; Zoccali, M.
VISTA Variables in the Vía Láctea (VVV) is a public ESO near-IR variability survey aimed at scanning the Milky Way Bulge and an adjacent section of the mid-plane. VVV observations started in October 2009 during ESO science verification. Regular observations for the first year of the survey have been conducted since February 2010 and will cover a total area of 520 square degrees in five passbands and five epochs. Here we address the first results obtained from the VVV Survey as well as the current status of the observations....
VISTA Variables in the Vía Láctea (VVV): Halfway Status and Results
(2014) Hempel, M.; Minniti, D.; Dékány, I.; Saito, R. K.; Lucas, P. W.; Emerson, J. P.; Ahumada, A. V.; Aigrain, S.; Alonso, M. V.; Alonso-García, J.; Amôres, E. B.; Angeloni, R.; Arias, J.; Bandyopadhyay, R.; Barbá, R. H.; Barbuy, B.; Baume, G.; Beamin, J. C.; Bedin, L.; Bica, E.; Borissova, J.; Bronfman, L.; Carraro, G.; Catelan, Marcio; Clariá, J. J.; Contreras, C.; Cross, N.; Davis, C.; de Grijs, R.; Drew, J. E.; Fariña, C.; Feinstein, C.; Fernández-Lajús, E. F.; Folkes, S.; Gamen, R. C.; Geisler, D.; Gieren, W.; Goldman, B.; González, O.; Gosling, A.; Gunthardt, G.; Gurovich, S.; Hambly, N. C.; Hanson, M.; Hoare, M.; Irwin, M. J.; Ivanov, V. D.; Jordán, A.; Kerins, E.; Kinemuchi, K.; Kurtev, R.; Longmore, A.; López-Corredoira, M.; Maccarone, T.; Martín, E.; Masetti, N.; Mennickent, R. E.; Merlo, D.; Messineo, M.; Mirabel, I. F.; Monaco, L.; Moni-Bidin, C.; Morelli, L.; Padilla, N.; Palma, T.; Parisi, M. C.; Parker, Q.; Pavani, D.; Pietrukowicz, P.; Pietrzynski, G.; Pignata, G.; Rejkuba, M.; Rojas, A.; Roman-Lopes, A.; Ruiz, M. T.; Sale, S. E.; Saviane, I.; Schreiber, M. R.; Schröder, A. C.; Sharma, S.; Smith, M.; Sodré, L., Jr.; Soto, M.; Stephens, A. W.; Tamura, M.; Tappert, C.; Thompson, M. A.; Toledo, I.; Valenti, E.; Vanzi, L.; Weidmann, W.; Zoccali, M.
The VISTA Variables in the Vía Láctea (VVV) survey is one of six near-infrared ESO public surveys, and is now in its fourth year of observing. Although far from being complete, the VVV survey has already delivered many results, some directly connected to the intended science goals (detection of variable stars, microlensing events, new star clusters), others concerning more exotic objects, e.g., novae. Now, at the end of the fourth observing period, and comprising roughly 50% of the proposed observations, the status of the survey, as well some of results based on the VVV data, are presented....

Browsing by Author "Dékány, I."

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