Browsing by Author "De Lee, Nathan"

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    Forty-four new and known M-dwarf multiples in the SDSS-III/APOGEE M-dwarf ancillary science sample
    (2018) Skinner, Jacob; Covey, Kevin R.; Bender, Chad F.; Rivera, Noah; De Lee, Nathan; Souto, Diogo; Chojnowski, Drew; Troup, Nicholas; Badenes, Carles; Minniti, D.; Bizyaev, Dmitry; Blake, Cullen H.
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    NGC 6304: a metal rich cluster with RR Lyrae?
    (2006) De Lee, Nathan; Catelan, Márcio; Layden, Andy; Pritzl, Barton; Smith, Horace; Sweigart, Allen; Welch, D. L.
    We have carried out a new search for variable stars in the metal-rich bulge globular cluster NGC 6304 ([Fe/H] = -0.59) using CCD observations obtained at CTIO. We used two data sets: one was taken on the 0.9m in May and June of 1996, and the second was taken on the 1m Yalo telescope in February and March of 2002. We have identified and obtained BVI light curves for 11 RR Lyrae stars, including 6 RRab and 5 RRc stars within the tidal radius of the cluster, and partial light curves for several long-period variables. Most of the RR Lyrae stars had been previously discovered, although not always recognized to be RR Lyrae type variables. We are able to exclude several RR Lyrae stars as probable field stars. In light of the large number of long-period RRab stars recently discovered within the metal-rich globular clusters NGC 6388 and NGC 6441, it is noteworthy that two of the possible RRab have periods greater than 0.8 days. The nature of these long-period RR Lyrae and the question of their membership will be discussed....
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    Physical parameters for RR Lyrae stars in the sdss filter system
    (2013) Catelan, Márcio; Torrealba, Gabriel I.; Cáceres, Claudio; Smith, Horace A.; De Lee, Nathan; Fitzgerald, Michael
    We present a calibration of the metallicity and physical parameters (temperature, luminosity, gravity, mass, radius) for RR Lyrae stars using the ugriz sdss photometric system. Our work is based on calculations of synthetic horizontal branches (HBs), fully taking into account evolutionary effects for a wide range in metallicities and HB morphologies. We provide analytical fits that are able to provide all quantities mentioned with very high (internal) precision, based solely on mean sdss magnitudes and colors....
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    RR Lyrae in the LMC: Insights Into the Oosterhoff Phenomenon
    (2013) Kuehn, Charles A; Smith, Horace A.; Catelan, Marcio; Jeon, Young-Beom; Nemec, James M.; Walker, Alistair R.; Kunder, Andrea; Dame, Kyra; Pritzl, Barton J.; De Lee, Nathan; Borissova, Jura
    Although more than eight decades have passed since P. Th. Oosterhoff drew attention to differences in the properties of RR Lyrae variables in globular clusters, the origin and significance of the Oosterhoff groups remain unclear. Nonetheless, the accumulation of extensive new observations of RR Lyrae stars in globular clusters of the Milky Way and Local Group galaxies allows a fresh look at the phenomenon. Insights come not only from surveys of variables within the original Oosterhoff groups I and II but also from recent observations of the Oosterhoff-intermediate systems found especially in smaller Local Group galaxies. We will compare properties of RR Lyrae in several systems to investigate what they reveal about system-to-system differences of transition temperature between fundamental-mode and first overtone pulsators and of horizontal branch luminosity. Both transition temperature and horizontal branch luminosity have at various times been credited as playing roles in the creation of the Oosterhoff dichotomy....