Examinando por Autor "Dekany, I"

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    Ítem
    Constraining dust extinction properties via the VVV survey
    (EDP SCIENCES, 2016-09) Majaess, D; Turner, D; Dekany, I; Minniti, D; Gieren, W
    Near-infrared color-excess and extinction ratios are essential for establishing the cosmic distance scale and probing the Galaxy, particularly when analyzing targets attenuated by significant dust. A robust determination of those ratios followed from leveraging new infrared observations from the VVV survey, wherein numerous bulge RR Lyrae and Type II Cepheids were discovered, in addition to BVJHKs(3.4 -> 22) mu m data for classical Cepheids and O stars occupying the broader Galaxy. The apparent optical color-excess ratios vary significantly with Galactic longitude (l), whereas the near-infrared results are comparatively constant with l and Galactocentric distance (E(J-(3.5 mu m) over bar /E(J - K-s) = 1.28 +/- 0.03. The results derived imply that classical Cepheids and O stars display separate optical trends (R-V,R-BV) with l, which appear to disfavor theories advocating a strict and marked decrease in dust size with increasing Galactocentric distance. The classical Cepheid, Type II Cepheid, and RR Lyrae variables are characterized by (A(J)/E(J-K-s) = (R-J,R-JKs) = 1.49 +/- 0.05 ((A(Ks)/A(J)) = 0.33 +/- 0.02), whereas the O stars are expectedly impacted by emission beyond 3.6 mu m. The mean optical ratios characterizing classical Cepheids and O stars are approximately (R-V,R-BV) similar to 3.1 and (R-V,R-BV) similar to 3.3, respectively.
  • Miniatura
    Ítem
    Variable stars in the Quintuplet stellar cluster with the VVV survey
    (OXFORD UNIV PRESS, 2016-10) Molina, CN; Borissova, J; Catelan, M; Alonso-Garcia, J; Kerins, E; Kurtev, R; Lucas, PW; Medina, N; Minniti, D; Dekany, I
    The Quintuplet cluster is one of the most massive star clusters in the Milky Way, situated very close to the Galactic Centre. We present a new search for variable stars in the vicinity of the cluster, using the five-year data base of the Vista Variables in the Via Lactea (VVV) ESO Public Survey in the near-infrared. A total of 7586 objects were identified in the zone around 2 arcmin from the cluster centre, using 55 K-S-band epochs. 33 stars show K-S-band variability, 24 of them being previously undiscovered. Most of the variable stars found are slow/semiregular variables, long-period variables of the Mira type, and OH/IR stars. In addition, a good number of our candidates show variations in a rather short time-scale. We also propose four young stellar object candidates, which could be cluster members.