Browsing by Author "Borissova, J"

Now showing 1 - 4 of 4
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    A catalogue of OB associations in IC 1613
    (2004) Borissova, J; Kurtev, R; Georgiev, L; Rosado, M
    We present a catalogue of OB associations in IC 1613. Using an automatic and objective method (Battinelli's 1991 technique) 60 objects were found. The size distribution reveals a significant peak at about 60 parsecs if a distance modulus of 24.27 mag is assumed. Spatial distributions of the detected associations and H II regions are strongly correlated.
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    Discovery of new Milky Way star cluster candidates in the 2MASS point source catalog. II. Physical properties of the star cluster CC01
    (2003) Borissova, J; Pessev, P; Ivanov, VD; Saviane, I; Kurtev, R; Ivanov, GR
    Three new obscured Milky Way clusters were detected as surface density peaks in the 2MASS point source catalog during our on-going search for hidden globular clusters and massive Arches-like star clusters. One more cluster was discovered serendipitously during a visual inspection of the candidates.
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    M75, a globular cluster with a trimodal horizontal branch.: II.: BV photometry of the RR lyrae variables
    (2003) Corwin, TM; Catelan, M; Smith, HA; Borissova, J; Ferraro, FR; Raburn, WS
    We present new BV CCD photometry, light curves, and ephemerides for nine previously known, 29 newly detected RR Lyrae variables, and one newly detected variable of an unknown type in the globular cluster M75. The photometry used for the detection of the additional variables was obtained with the image subtraction package ISIS. The data were acquired on an observing run in 1999 July and range over seven observing nights. Estimates of fundamental photometric parameters are presented including intensity- and magnitude-averaged B and V magnitudes, magnitude-averaged colors, pulsation periods, and pulsation amplitudes. The mean period of the RRab variables, [P-ab] = 0.5868 days, and the number fraction of RRc stars, N-c/N-RR = 0.342, are both large for an Oosterho. type I (OoI) globular cluster, suggesting that M75 may be Oosterhoff-intermediate. Possible conflicts between Oosterhoff-type determination based on the A(V)-log P and A(B)-log P diagrams are discussed. The physical parameters of the RRc and RRab variables, as obtained from Fourier decomposition of their light curves, do not show any clear deviation from normal OoI behavior.
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    New metallicities of RR Lyrae stars in ω Centauri
    (2006) Sollima, A; Borissova, J; Catelan, M; Smith, HA; Minniti, D; Cacciari, C; Ferraro, FR
    We present new spectroscopic metal abundances for 74 RR Lyrae (RRL) stars in omega Cen obtained with FLAMES. The well-known metallicity spread is visible among the RRL variables. The metal-intermediate (MI) RRL stars ([Fe/H] similar to -1.7) are fainter than the bulk of the dominant metal-poor population ([Fe/H] similar to -1.7), in good agreement with the corresponding zero-age horizontal-branch models with cosmological helium abundance. This result Y = 0.246 conflicts with the hypothesis that the progenitors of the MI RRL stars correspond to the anomalous blue main-sequence stars, which share a similar metallicity but whose properties are currently explained by assuming for them a large helium enhancement. Therefore, in this scenario, the coexistence within the cluster of two different populations with similar metallicities ([Fe/H] similar to -1.7) and different helium abundances has to be considered.