Browsing by Author "Dékány, István"
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- ItemPulsating stars in ω Centauri. Near-IR properties and period-luminosity relations(2017) Navarrete, Camila; Catelan, Marcio; Contreras Ramos, Rodrigo; Alonso-García, Javier; Gran, Felipe; Dékány, István; Minniti, Danteω Centauri (NGC 5139) contains many variable stars of different types, including the pulsating type II Cepheids, RR Lyrae and SX Phoenicis stars. We carried out a deep, wide-field, near-infrared (IR) variability survey of ω Cen, using the VISTA telescope. We assembled an unprecedented homogeneous and complete J and KS near-IR catalog of variable stars in the field of ω Cen. In this paper we compare optical and near-IR light curves of RR Lyrae stars, emphasizing the main differences. Moreover, we discuss the ability of near-IR observations to detect SX Phoenicis stars given the fact that the amplitudes are much smaller in these bands compared to the optical. Finally, we consider the case in which all the pulsating stars in the three different variability types follow a single period-luminosity relation in the near-IR bands....
- 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 Hidden Potential of VVV RR Lyrae Light Curves(2018) Hajdu, Gergely; Catelan, Marcio; Dékány, István; Grebel, Eva K.We introduce a new method of determining the average magnitudes of RR Lyrae variables: in the K_{S}-band, based on robust fitting of principal components from a high-quality training sample; in the J-band, using the amplitudes of the K_{S} principal components to approximate the J-band light-curve shape in each pulsation phase. Furthermore, it has been found that the metallicity of individual RR Lyrae variables can be inferred from the K_{S}-band light curves....
- ItemVariable stars in the VVV globular clusters(2017) Alonso-García, Javier; Catelan, Marcio; Ramos, Rodrigo Contreras; Dékány, István; Minniti, DanteThe VVV survey observed some of the most crowded and most obscured regions in the inner MilkyWay during the last years. A significant sample of the less known globular clusters in our galaxy lie there. Combining the high-resolution, wide-field, nearinfrared capabilities of the survey camera, the use of 5 different filters, and multi-epoch observations, we are able to overcome many of the previous challenges that prevented a proper study of these objects. Particularly, the identification of the RR Lyrae stars in these globular clusters is proving to be a fundamental tool to establish accurately their distances and reddenings, and to infer information about the Oosterhoff dichotomy that Galactic globular clusters seem to follow.
- 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.
- ItemVisual - near-infrared properties of the interstellar extinction towards the Galactic bulge with RR Lyrae stars(2018) Hajdu, Gergely; Catelan, Marcio; Dékány, István; Grebel, EvaTowards the bulge, studies of interstellar extinction are generally limited by uncertainties in the individual distances, magnitudes, and colors of the most commonly utilized stellar tracers. RR Lyrae stars, however, have well known absolute magnitudes and colors; furthermore, their distribution is known to be strongly centered around the Galactic center, easing the problem of unknown individual distances. We exploit these properties of RR Lyrae variables with large samples derived from wide-area surveys (OGLE, VVV) to study the interstellar extinction in optical and near-infrared wavelengths towards the Galactic bulge....