Papers on Omega Cen, NGC6440, NGC6388, NGC6441, M4…

Hello, here is a brief list (not sure if complete…) with the latest preprints regarding Galactic Globular Clusters, which appeared this month on astro-ph:

• Abundances on the Main Sequence of Omega Centauri

  Authors: Laura M. Stanford, G. S. Da Costa, John E. Norris

• Chemical Abundances and Kinematics in Globular Clusters and Local Group Dwarf Galaxies and Their Implications for Formation Theories of the Galactic Halo
  

  Authors: Doug Geisler (Universidad de Concepcion), George Wallerstein (University of Washington), Verne V. Smith (National Optical Astronomy Observtory), Dana I. Casetti-Dinescu (Yale University)

• Discovery of 442-Hz Pulsations from an X-ray Source in the Globular Cluster NGC 6440

  Authors: Fotis P. Gavriil, Tod E. Strohmayer, Jean H. Swank, Craig B. Markwardt

• The Peculiar Horizontal Branch Morphology of the Galactic Globular Clusters NGC 6388 and NGC 6441: new insights from UV observations

  Authors: G. Busso, S. Cassisi, G. Piotto, M. Castellani, M. Romaniello, M. Catelan, S. G. Djorgovski, A. Recio Blanco, A. Renzini, M. R. Rich, A. V. Sweigart, M. Zoccali

• Intermittent millisecond X-ray pulsations from the neutron-star X-ray transient SAX J1748.9-2021 in the globular cluster NGC 6440

  Authors: D. Altamirano, P. Casella, A. Patruno, R. Wijnands, M. van der Klis

• A search for solar-like oscillations in K giants in the globular cluster M4

  Authors: S. Frandsen, H. Bruntt, F. Grundahl, G. Kopacki, H. Kjeldsen, T. Arentoft, D. Stello, T. R. Bedding, A. P. Jacob, R. L. Gilliland, P. D. Edmonds, E. Michel, J. Matthiesen

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Deep HST Photometry of NGC 6388: Age and Horizontal Branch Luminosity

NGC 6388 :: New preprint

M. Catelan et al.

Deep HST Photometry of NGC 6388: Age and Horizontal Branch Luminosity

Abstract:
Using the Hubble Space Telescope, we have obtained the first color-magnitude diagram (CMD) to reach the main-sequence turnoff of the Galactic globular cluster NGC 6388. From a comparison between the cluster CMD and 47 Tucanae’s, we find that the bulk of the stars in these two clusters have nearly the same age and chemical composition. On the other hand, our results indicate that the blue horizontal branch and RR Lyrae components in NGC 6388 are intrinsically overluminous, which must be due to one or more, still undetermined, non-canonical second parameter(s) affecting a relatively minor fraction of the stars in NGC 6388.

http://it.arxiv.org/abs/astro-ph/0609727

Deep HST Photometry of NGC 6388: Age and Horizontal Branch Luminosity

NGC 6388 :: New preprint

M. Catelan et al.

Deep HST Photometry of NGC 6388: Age and Horizontal Branch Luminosity

Abstract:
Using the Hubble Space Telescope, we have obtained the first color-magnitude diagram (CMD) to reach the main-sequence turnoff of the Galactic globular cluster NGC 6388. From a comparison between the cluster CMD and 47 Tucanae’s, we find that the bulk of the stars in these two clusters have nearly the same age and chemical composition. On the other hand, our results indicate that the blue horizontal branch and RR Lyrae components in NGC 6388 are intrinsically overluminous, which must be due to one or more, still undetermined, non-canonical second parameter(s) affecting a relatively minor fraction of the stars in NGC 6388.

http://it.arxiv.org/abs/astro-ph/0609727

Hot horizontal-branch stars in the metal-rich bulge globular cluster NGC6388…

NGC 6388 :: New published paper

S. Moehler and A. V. Sweigart

Observations of the hot horizontal-branch stars in the metal-rich bulge globular cluster NGC6388 – Indications of helium enrichment and a lesson in crowded field spectroscopy.

A&A 455 (2006) 943-952
(Section ‘Galactic structure, stellar clusters, and populations’)

http://publish.edpsciences.org/abstract/aa/v455/p943

Image-Subtraction Photometry of Variable Stars in NGC 6388 and NGC 6441

New paper (“The Astronomical Journal”, Volume 132):

Corwin, T. Michael; Sumerel, Andrew N.; Pritzl, Barton J.; Smith, Horace A.; Catelan, M.; Sweigart, Allen V.; Stetson, Peter B.

Image-Subtraction Photometry of Variable Stars in the Globular Clusters NGC 6388 and NGC 6441

We have applied Alard’s image-subtraction method (ISIS ver. 2.1) to the observations of the globular clusters NGC 6388 and NGC 6441 previously analyzed using standard photometric techniques (DAOPHOT and ALLFRAME). In this reanalysis of observations obtained at the Cerro Tololo Inter-American Observatory, besides recovering the variables previously detected on the basis of our ground-based images, we have also been able to recover most of the RR Lyrae variables previously detected only in the analysis of Hubble Space Telescope WFPC2 observations of the inner region of NGC 6441. In addition, we report five possible new variables not found in the analysis of the Hubble Space Telescope observations of NGC 6441. This dramatically illustrates the capabilities of image-subtraction techniques applied to ground-based data to recover variables in extremely crowded fields. We have also detected 12 new variables and 6 possible variables in NGC 6388 not found in our previous ground-based studies. The revised mean period for RRab stars in NGC 6388 is 0.676 days, while the mean period of RRab stars in NGC 6441 is unchanged at 0.759 days. These values are among the largest known for any Galactic globular cluster. Additional probable type II Cepheids were identified in NGC 6388, confirming its status as a metal-rich globular cluster rich in Cepheids.

ADS link to the paper

(mcastel)