Browsing by Author "Buonanno, R."

Now showing 1 - 5 of 5
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    New near-infrared JHKs light-curve templates for RR Lyrae variables
    (2019) Braga, V. F.; Stetson, P. B.; Bono, G.; Dall'Ora, M.; Ferraro, I; Fiorentino, G.; Iannicola, G.; Inno, L.; Marengo, M.; Neeley, J.; Beaton, R. L.; Buonanno, R.; Calamida, A.; Ramos, R. Contreras; Chaboyer, B.; Fabrizio, M.; Freedman, W. L.; Gilligan, C. K.; Johnston, K., V; Lub, J.; Madore, B. F.; Magurno, D.; Marconi, M.; Marinoni, S.; Marrese, P. M.; Mateo, M.; Matsunaga, N.; Minniti, D.; Monson, A. J.; Monelli, M.; Nonino, M.; Persson, S. E.; Pietrinferni, A.; Sneden, C.; Storm, J.; Walker, A. R.; Valenti, E.; Zoccali, M.
    We provide homogeneous optical (UBVRI) and near-infrared (NIR, JHK) time series photometry for 254 cluster (omega Cen, M 4) and field RR Lyrae (RRL) variables. We ended up with more than 551 000 measurements, of which only 9% are literature data. For 94 fundamental (RRab) and 51 first overtones (RRc) we provide a complete optical/NIR characterization (mean magnitudes, luminosity amplitudes, epoch of the anchor point). The NIR light curves of these variables were adopted to provide new light-curve templates for both RRc and RRab variables. The templates for the J and the H bands are newly introduced, together with the use of the pulsation period to discriminate among the different RRab templates. To overcome subtle uncertainties in the fit of secondary features of the light curves we provide two independent sets of analytical functions (Fourier and periodic Gaussian series). The new templates were validated by using 26 omega Cen and Bulge RRLs. We find that the difference between the measured mean magnitude along the light curve and the mean magnitude estimated by using the template on a single randomly extracted phase point is better than 0.01 mag (sigma = 0.04 mag). We also validated the template on variables for which at least three phase points were available, but without information on the phase of the anchor point. We find that the accuracy of the mean magnitudes is also similar to 0.01 mag (sigma = 0.04 mag). The new templates were applied to the Large Magellanic Cloud (LMC) globular cluster Reticulum and by using literature data and predicted PLZ relations we find true distance moduli mu = 18.47 +/- 0.10 (rand.) +/- 0.03 (syst.) mag (J) and 18.49 +/- 0.09 +/- 0.05 mag (K). We also used literature optical and mid-infrared data and we found a mean mu of 18.47 +/- 0.02 +/- 0.06 mag, suggesting that Reticulum is similar to 1 kpc closer than the LMC.
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    ON THE RADIAL DISTRIBUTION OF HORIZONTAL BRANCH STARS IN NGC 2808
    (2009) Iannicola, G.; Monelli, M.; Bono, G.; Stetson, P. B.; Buonanno, R.; Calamida, A.; Zoccali, M.; Caputo, F.; Castellani, M.; Corsi, C. E.; Dall'Ora, M.; Di Cecco, A.; Degl'Innocenti, S.; Ferraro, I.; Nonino, M.; Pietrinferni, A.; Pulone, L.; Moroni, P. G. Prada; Romaniello, M.; Sanna, N.; Walker, A. R.
    We present accurate new ultraviolet and optical BVI photometry for the Galactic globular cluster NGC 2808 based on both ground-based and archival Hubble Space telescope imagery. From this we have selected a sample of similar to 2000 Horizontal Branch (HB) stars; given the extensive wavelength range considered and the combination of both high angular resolution and wide-field photometric coverage, our sample should be minimally biased. We divide the HB stars into three radial bins and find that the relative fractions of cool, hot, and extreme HB stars do not change radically when moving from the center to the outskirts of the cluster: the difference is typically smaller than similar to 2 sigma. These results argue against the presence of strong radial differentiation among any stellar subpopulations having distinctly different helium abundances. The ratio between HB and red giant (RG) stars brighter than the ZAHB steadily increases when moving from the innermost to the outermost cluster regions. The difference is larger than similar to 4 sigma and indicates a deficiency of bright RGs in the outskirts of the cluster.
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    ON THE ΔVHBbump PARAMETER IN GLOBULAR CLUSTERS
    (2010) Di Cecco, A.; Bono, G.; Stetson, P. B.; Pietrinferni, A.; Becucci, R.; Cassisi, S.; Degl'Innocenti, S.; Iannicola, G.; Moroni, P. G. Prada; Buonanno, R.; Calamida, A.; Caputo, F.; Castellani, M.; Corsi, C. E.; Ferraro, I.; Dall'Ora, M.; Monelli, M.; Nonino, M.; Piersimoni, A. M.; Pulone, L.; Romaniello, M.; Salaris, M.; Walker, A. R.; Zoccali, M.
    We present new empirical estimates of the del V-HB(bump) parameter for 15 Galactic globular clusters (GGCs) using accurate and homogeneous ground-based optical data. Together with similar evaluations available in the literature, we ended up with a sample of 62 GGCs covering a very broad range in metal content (-2.16 dex <= [M/H] <= -0.58 dex). Adopting the homogeneous metallicity scale provided either by Kraft & Ivans or by Carretta et al., we found that the observed del V-HB(bump) parameters are larger than predicted. In the metal-poor regime ([M/H] less than or similar to -1.7, -1.6 dex) 40% of GCs show discrepancies of 2s (approximate to 0.40 mag) or more. Evolutionary models that account either for alpha- and CNO-enhancement or for helium enhancement do not alleviate the discrepancy between theory and observations. The outcome is the same if we use the new solar heavy-element mixture. The comparison between alpha- and CNO-enhanced evolutionary models and observations in the Carretta et al. metallicity scale also indicates that observed del V-HB(bump) parameters, in themetal- rich regime ([M/H] >= 0), might be systematically smaller than predicted.
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    Stromgren and near-infrared photometry of metal-rich bulge globular clusters I. NGC 6528 and its surrounding field
    (2014) Calamida, A.; Bono, G.; Lagioia, E.P.; Milone, A.P.; Fabrizio, M.; Saviane, I.; Moni Bidin, C.; Mauro, F.; Buonanno, R.; Zoccali, Manuela
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    The soundtrack of RR Lyrae in omega Cen at high-frequency.
    (2015) Calamida, A.; Randall, S. K.; Monelli, M.; Bono, G.; Buonanno, R.; Strampelli, G.; Catelan, Marcio; Van Grootel, V.; Alonso, M. L.; Stetson, P. B.; Stellingwerf, R. F.
    We present preliminary Sloan u',g'-band light curves for a sample of known RR Lyrae variables in the Galactic globular cluster omega Cen. Results are based on the partial reduction of multi-band time series photometric data collected during six consecutive nights with the visitor instrument ULTRACAM mounted on the New Technology Telescope (La Silla, ESO). This facility allowed us to simultaneously observe in three different bands (Sloan u',g',r') a field of view of ∼ 6×6 arcminutes. The telescope and the good seeing conditions allowed us to sample the light curves every 15 seconds. We ended up with a data set of ∼ 6,000 images per night per filter, for a total of more than 200,000 images of the selected field. This data set allowed us to detect different kind of variables, such as RR-Lyraes, SX Phoenicis, eclipsing binaries, semi-regulars. More importantly, we were able for the first time to sample at high-frequency cluster RR Lyraes in the u',g'-band and to show in detail the pulsation phases across the dip located along the rising branch of RR-Lyraes. Based on data collected with ULTRACAM@NTT (La Silla, ESO, PID: 087.D-0216)...