Browsing by Author "Pritzl, B. J."
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- ItemA Search for EHB Pulsators in the Globular Cluster NGC 6752(2007) Catelan , Marcio; Prieto, G. E.; Zoccali, M.; Weidner, C.; Stetson, P. B.; Moni Bidin, C.; Altmann, M.; Smith, H. A.; Pritzl, B. J.; Borissova, J.; de Medeiros, J. R.We describe the status of a project whose main goal is to detect variability along the extreme horizontal branch of the globular cluster NGC 6752. Based on Magellan 6.5-m data, preliminary light curves are presented for some candidate variables. By combining our time-series data, we also produce a deep CMD of unprecedented quality for the cluster which reveals a remarkable lack of main sequence binaries, possibly pointing to a low primordial binary fraction....
- ItemMetal-Rich Globular Clusters and the Second-Parameter Effect: NGC 6388, NGC 6441(2002) Pritzl, B. J.; Smith, H. A.; Catelan, Márcio; Sweigart, AllenThe second-parameter effect has long challenged our understanding of stellar popullations in global clusters. The RR Lyrae star can be used to examine the effects additional parameters have on the horizontal branch (...)
- ItemRR Lyrae in the Large Magellanic Cloud: New Insights Into Oosterhoff Intermediate Globular Clusters(2013) Kuehn, Charles A.; Smith, H. A.; Catelan, Marcio; Pritzl, B. J.; De Lee, N. M.; Borissova, J.Current models suggest that the Milky Way halo was formed through the accretion of objects similar to the present day nearby dwarf galaxies. The ancient nature of RR Lyrae stars make them ideal tracers of stellar populations that can be used to determine how similar the present day dwarf galaxies are to the objects that were accreted to form the Milky Way halo. Globular clusters in the halo can be divided into two groups based on the properties of their RR Lyrae stars, called Oosterhoff groups, with a zone of avoidance between these groups. Nearby dwarf galaxies and their globular clusters fall not only in the Oosterhoff I and II groups, like in the Milky Way, but also in the zone of avoidance between these groups. These Oosterhoff intermediate objects, as the objects that fall in the zone of avoidance are called, present a challenge to the current theories of Milky Way halo formation. We present results of a recent study of globular clusters in the Large Magellanic Cloud which focused on the behavior of individual RR Lyrae stars in Oosterhoff intermediate objects and how this behavior compares to RR Lyrae stars in the other Oosterhoff groups. We discuss how these results demonstrate that Oosterhoff intermediate objects should not be thought of as one homogenous group. We also discuss how these results suggest that the traditional dividing lines between the Oosterhoff groups may need to be revised....
- ItemStellar populations of the newly discovered satellites of the Milky Way .(2008) Dall'Ora, M.; Clementini, G.; Ripepi, V.; Kinemuchi, K.; Greco, C.; Kuehn, C.; Musella, I.; Rodgers, C. T.; Di Fabrizio, L.; Beers, T. C.; Catelan, Marcio; Marconi, M.; Pritzl, B. J.; Smith., H. A.We have carried out an extensive observing campaign on the new dwarf spheroidal galaxies (dSphs) recently discovered by the SDSS, with the aim of characterizing their stellar populations and structural properties, as well as their variable star content. First preliminary results are presented for the Canes Venatici II, the Coma and the Ursa Major II dSphs, based on data collected at a variety of telescopes, and reaching each galaxy's Main Sequence Turn-Off (MSTO)....
- ItemThe globular cluster M 69: color-magnitude diagram and variable stars(2010) Escobar, M. E.; Catelan, Marcio; Zoccali, M.; Smith, H. A.; Pritzl, B. J.; Layden, A.; Gregorsok, J.; Welch, D. L.; Webb, T.We present BV photometry and the results of a search for stellar variability in the Galactic globular cluster M 69. The resulting color-magnitude diagram shows significant contamination by field stars. In our variability search we found 62 variable stars, 54 of which were new discoveries....
- ItemThe globular cluster NGC 5286: color-magnitude diagram and variable stars(2010) Zorotovic, M.; Catelan, Marcio; Zoccali, M.; Smith, H. A.; Pritzl, B. J.We present BV photometry and the results of a search for stellar variability in the globular cluster NGC 5286, which has tentatively been associated with the Canis Major dwarf spheroidal galaxy. Our results indicate an Oosterhoff type II for the cluster, which is unusual for an object of extragalactic origin....
- ItemVariable Stars in Large Magellanic Cloud Globular Clusters. III. Reticulum(2013) Kuehn, C. A.; Dame, K.; Smith, H. A.; Catelan, Márcio; Walker, A. R.; Kunder, A.; Pritzl, B. J.; De Lee, N.; Borissova, J.
- ItemVariable Stars in the Globular Clusters and in the Field of the Fornax dSph Galaxy(2009) Greco, C.; Clementini, G.; Held, E. V.; Poretti, E.; Catelan, Marcio; Dell'Arciprete, L.; Gullieuszik, M.; Maio, M.; Rizzi, L.; Smith, H. A.; Pritzl, B. J.; Rest, A.; de Lee, N.Variable stars have been identified for the first time in Fornax 4, the globular cluster located near the center of the Fornax dwarf spheroidal galaxy. By applying the image-subtraction technique to B and V time series photometry obtained with the MagIC camera of the 6.5 m Magellan Clay telescope and with the wide field imager of the 4 m Blanco CTIO telescope, we detected 27 RR Lyrae stars (22 fundamental-mode, 3 first-overtone, and 2 double-mode pulsators) in a 2.4'×2.4' area centered on Fornax 4. The average and minimum periods of the ab-type RR Lyrae stars, =0.594 days and Pab,min=0.5191 days, respectively, as well as the revised position of the cluster in the horizontal branch type-metallicity plane, all consistently point to an Oosterhoff-intermediate status for the cluster, unlike what is seen for the vast majority of Galactic globular clusters, but in agreement with previous indications for the other globular clusters in Fornax. The average apparent magnitude of the RR Lyrae stars located within 30" from the cluster center is =21.43+/-0.03 mag (σ=0.10 mag, average of 12 stars), leading to a true distance modulus of μ0=20.64+/-0.09 mag or μ0=20.53+/-0.09 mag, depending on whether a low ([Fe/H]=-2.0) or a moderately high ([Fe/H]=-1.5) metallicity is adopted.
- ItemVariable Stars in the Inner Region of NGC 6388(2005) Pritzl, B. J.; Stetson, P. B.; Smith, H. A.; Catelan, Marcio; Layden, A. C.; Kinemuchi, K.; Rich, R. M.; Sweigart, A. V.The metal-rich globular clusters NGC 6388 and NGC 6441 ([Fe/H] ∼-0.6) have unusual sloping blue horizontal branches that extend from a prominent red clump through the RR Lyrae instability strip to a well-populated blue tail. The RR Lyrae variables found from ground-based studies in these clusters have unusually long periods for their metallicities and may represent a new Oosterhoff group. As part of a Hubble Space Telescope Snapshot program we have obtained ACS images of the inner, compact region of NGC 6388 and use archival WFPC2 images to search for additional variable stars. Here we present the results of this variable star search. The properties of the newly discovered RR Lyrae variables will be used to further define the nature of these unusual globular clusters. We gratefully acknowledge financial support through the HST grant GO-09821.09-A.