Browsing by Author "Minniti, Dante"

Now showing 1 - 11 of 11
  • No Thumbnail Available
    Item
    HST photometry of the binary globular cluster sersic 13N-S in NGC5128[1]
    (2009) Villegas Mansilla, Daniela Muriel; Minniti, Dante; Funes, J. G.; Richtler, Tom; Larsen, Søren
  • No Thumbnail Available
    Item
    PEERING THROUGH THE DUST: PRECISE ASTROMETRY IN THE GALACTIC MID-PLANE WITH THE VVV SURVEY
    (2015) Lucas, PW; Smart, RL; Jones, HRA; Kurtev, R; Beamin Muhlenbrock, Juan Carlos; Borissova, J.; Gromadzki, Grzegorz; Ivanov, Valentin; Minniti, Dante; Pinfield, DJ
    Gaia will see little of the Galactic mid-plane and nuclear bulge due to high extinction at optical wavelengths. To study the structure and kinematics of the inner Galaxy we must look to longer wavelengths. The Vista Variables in the Via Lactea (VVV, Minniti et al. 2010) survey currently provides just over 4 years of observations covering approximately 560 square degrees of the Galactic bulge and plane. Typically each source is observed 50-150 times in the Ks band over this period. Using these data we provide relative proper motions for approximately 200 million unique sources down to Ks similar to 16 with uncertainties approaching 1 mas yr(-1). In addition, we fit a solution of the parallactic motion of all sources with significant proper motion and discover a number of new nearby brown dwarfs. These results will allow us to identify faint common proper motion companions to stars with Gaia parallaxes, increasing the number of brown dwarf benchmark objects. Our absolute astrometric calibration precision is currently similar to 2 mas yr(-1), based on PPMXL. The Gaia absolute astrometric reference grid will allow us to precisely anchor our results and measure the streaming motions of stars in the bulge. Finally, we anticipate that the catalogue could provide kinematic distances to the numerous optically invisible high amplitude variable stars that VVV is discovering.
  • No Thumbnail Available
    Item
    Proper motions and brown dwarfs in the VVV survey
    (2014) Beamín Muhlenbrock, Juan Carlos; Minniti, Dante; Gromadzki, M.; Kurtev, R.; Ivanov, V. D.; Peña Ramírez, Karla Yulien; Saito, R. K.; Borissova, J.
    We use the first three years of observations of the VISTA Variables in the Via Lactea Survey, to create a catalog of high proper motion objects, and search for nearby objects, here we describe the initial results including the discovery the first brown dwarf in the VVV survey.
  • Thumbnail Image
    Item
    Properties of RR Lyrae stars in the inner regions of the Large Magellanic Cloud. II. The extended sample
    (2007) Borissova, J.; Minniti, Dante; Rejkuba, M.; Alves, D.
  • Thumbnail Image
    Item
    Pulsating 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, Dante
    ω 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....
  • No Thumbnail Available
    Item
    Searching for extragalactic sources in the VISTA variables in the VÍa láctea survey
    (2018) Baravalle, Laura D.; Victoria Alonso, M.; Castellón, José Luis Nilo; Beamin Muhlenbrock, Juan Carlos; Minniti, Dante
    We search for extragalactic sources in the VISTA Variables in the Vía Láctea survey that are hidden by the Galaxy. Herein, we describe our photometric procedure to find and characterize extragalactic objects using a combination of SExtractor and PSFEx. It was applied in two tiles of the survey: d010 and d115, without previous extragalactic IR detections, in order to obtain photometric parameters of the detected sources. The adopted criteria to define extragalactic candidates include CLASS-STAR < 0.3; 1.0 < R1 2 < 5.0 arcsec; 2.1 < C < 5; and F > 0.002 and the colors: 0.5 < (J-Ks) < 2.0 mag; 0.0 < (J-H) < 1.0 mag; 0.0 < (H-Ks) < 2.0 mag and (J-H) + 0.9 (H-Ks) > 0.44 mag. We detected 345 and 185 extragalactic candidates in the d010 and d115 tiles, respectively. All of them were visually inspected and confirmed to be galaxies. In general, they are small and more circular objects, due to the near-IR sensitivity to select more compact objects with higher surface brightness. The procedure will be used to identify extragalactic objects in other tiles of the VVV disk, which will allow us to study the distribution of galaxies and filaments hidden by the Milky Way. © 2018. The American Astronomical Society. All rights reserved.
  • No Thumbnail Available
    Item
    Stellar 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, Maren
    The 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....
  • Thumbnail Image
    Item
    The 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, Jason
    We 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.
  • No Thumbnail Available
    Item
    Variable stars in the VVV globular clusters
    (2017) Alonso-García, Javier; Catelan, Marcio; Ramos, Rodrigo Contreras; Dékány, István; Minniti, Dante
    The 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.
  • Thumbnail Image
    Item
    Variable stars in the VVV globular clusters. II. NGC 6441, NGC 6569, NGC 6626 (M 28), NGC 6656 (M 22), 2MASS-GC 02, and Terzan 10
    (2021) Alonso-García, Javier; Smith, Leigh C.; Catelan, Márcio; Minniti, Dante; Navarrete, Camila; Borissova, Jura; Carballo-Bello, Julio A.; Contreras Ramos, Rodrigo; Fernández-Trincado, José G.; Ferreira Lopes, Carlos E.; Gran, Felipe; Garro, Elisa R.; Geisler, Doug; Guo, Zhen; Hempel, Maren; Kerins, Eamonn; Lucas, Philip W.; Palma, Tali; Peña Ramírez, Karla; Ramírez Alegría, Sebastián; Saito, Roberto K.
    Context. The Galactic globular clusters (GGCs) located in the inner regions of the Milky Way suffer from high extinction that makes their observation challenging. High densities of field stars in their surroundings complicate their study even more. The VISTA Variables in the Via Lactea (VVV) survey provides a way to explore these GGCs in the near-infrared where extinction effects are highly diminished. Aims: We conduct a search for variable stars in several inner GGCs, taking advantage of the unique multi-epoch, wide-field, near-infrared photometry provided by the VVV survey. We are especially interested in detecting classical pulsators that will help us constrain the physical parameters of these GGCs. In this paper, the second of a series, we focus on NGC 6656 (M 22), NGC 6626 (M 28), NGC 6569, and NGC 6441; these four massive GGCs have known variable sources, but quite different metallicities. We also revisit 2MASS-GC 02 and Terzan 10, the two GGCs studied in the first paper of this series. Methods: We present an improved method and a new parameter that efficiently identify variable candidates in the GGCs. We also use the proper motions of those detected variable candidates and their positions in the sky and in the color-magnitude diagrams to assign membership to the GGCs. Results: We identify and parametrize in the near-infrared numerous variable sources in the studied GGCs, cataloging tens of previously undetected variable stars. We recover many known classical pulsators in these clusters, including the vast majority of their fundamental mode RR Lyrae. We use these pulsators to obtain distances and extinctions toward these objects. Recalibrated period-luminosity-metallicity relations for the RR Lyrae bring the distances to these GGCs to a closer agreement with those reported by Gaia, except for NGC 6441, which is an uncommon Oosterhoff III GGC. Recovered proper motions for these GGCs also agree with those reported by Gaia, except for 2MASS-GC 02, the most reddened GGC in our sample, where the VVV near-infrared measurements provide a more accurate determination of its proper motions. Lightcurves and full Tables 2, 5, 6, 7, 8, and 9 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/651/A47...
  • No Thumbnail Available
    Item
    Variable Stars in VVV Globular Clusters
    (2015) Contreras Ramos, Rodrigo; Alonso-Garcia, Javier; Minniti, Dante; Catelan, Márcio; Zoccali, Manuela; Gran, Felipe; Dekany, Istvan
    The 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.