Gclusters preprints

[0912.0824] On a new Near-Infrared method to estimate the absolute ages of star clusters: NGC3201 as a first test case

Mon, 07 Dec 2009 14:25:35 +0100

[0912.0824] On a new Near-Infrared method to estimate the absolute ages of star clusters: NGC3201 as a first test case:

G. Bono et al.:: We present a new method to estimate the absolute ages of stellar systems. This method is based on the difference in magnitude between the main sequence turn-off (MSTO) and a well defined knee located along the lower main sequence (MSK).

[0912.0192] The cluster Terzan 5 as a remnant of a primordial building block of the Galactic bulge

Wed, 02 Dec 2009 11:43:59 +0100

[0912.0192] The cluster Terzan 5 as a remnant of a primordial building block of the Galactic bulge:

F. R. Ferraro et al :: …Here we report that Terzan 5, a globular-cluster-like system in the Galactic bulge, has two stellar populations with different iron content and ages. Terzan 5 could be the surviving remnant of one of the primordial building blocks that are thought to merge and form galaxy bulges.

[0911.5356] The Presence of Two Distinct Red Giant Branches in the Globular Cluster NGC 1851

Tue, 01 Dec 2009 11:52:15 +0100

[0911.5356] The Presence of Two Distinct Red Giant Branches in the Globular Cluster NGC 1851:

Sang-Il Han et al. :: …Here we show from the CTIO 4m UVI photometry of the globular cluster NGC 1851 that its RGB is clearly split into two in the U - I color. The two distinct RGB populations are also clearly separated in the abundance of heavy elements as traced by Calcium, suggesting that the type II supernovae enrichment is also responsible, in addition to the pollutions of lighter elements by intermediate mass asymptotic giant branch stars or fast-rotating massive stars….

[0911.4743] A Blue Tilt in the Globular Cluster System of the Milky Way-like Galaxy NGC 5170

Thu, 26 Nov 2009 15:18:12 +0100

[0911.4743] A Blue Tilt in the Globular Cluster System of the Milky Way-like Galaxy NGC 5170:

Duncan Forbes, Lee Spitler, William Harris, Jeremy Bailin, Jay Strader, Jean Brodie, Soeren Larsen :: Here we present HST/ACS imaging, in the B and I bands, of the edge-on Sb/Sc galaxy NGC 5170. Excluding the central disk region region, we detect a 142 objects with colours and sizes typical of globular clusters (GCs)…

[0911.0444] Discovery of a Second Transient Low-Mass X-ray Binary in the Globular Cluster NGC 6440

Wed, 04 Nov 2009 11:46:00 +0100

[0911.0444] Discovery of a Second Transient Low-Mass X-ray Binary in the Globular Cluster NGC 6440:

C. O. Heinke et al. :: We have identified a new transient luminous low-mass X-ray binary, NGC 6440 X-2, with Chandra/ACIS, RXTE/PCA, and Swift/XRT observations of the globular cluster NGC 6440….

[0911.0420] The globular cluster system of NGC 1399 V. dynamics of the cluster system out to 80 kpc

Wed, 04 Nov 2009 11:44:58 +0100

[0911.0420] The globular cluster system of NGC 1399 V. dynamics of the cluster system out to 80 kpc:

Y. Schuberth, T. Richtler, M. Hilker, B. Dirsch, L. P. Bassino, A. J. Romanowsky, L. Infante :: We use the largest set of globular cluster velocities obtained so far of any elliptical galaxy to revise and extend the previous investigations of the dynamics of NGC 1399, the central dominant galaxy of the nearby Fornax cluster of galaxies…

[0910.5609] An Unusual Eclipsing Blue Straggler V8-NGC 6752

Fri, 30 Oct 2009 16:04:23 +0100

[0910.5609] An Unusual Eclipsing Blue Straggler V8-NGC 6752:

J. Kaluzny, M. Rozyczka, I.B. Thompson, K. Zloczewski ..We report the analysis of a binary blue straggler in NGC 6752 with a short orbital period of 0.315 d and a W UMA-type light curve…

[0909.0983] Lithium in the Globular Cluster NGC 6397: Evidence for dependence on evolutionary status

Wed, 14 Oct 2009 16:33:26 +0200

[0909.0983] Lithium in the Globular Cluster NGC 6397: Evidence for dependence on evolutionary status:

J. I. Gonzalez Hernandez, P. Bonifacio, E. Caffau, M. Steffen, H.-G. Ludwig, N. T. Behara, L. Sbordone, R. Cayrel, S. Zaggia :: Most Globular Clusters are believed to host a single stellar populations. They can thus be considered a good place to study the Spite plateau and probe for possible evolutionary modifications of the Li content. We want to determine the Li content of subgiant (SG) and Main Sequence (MS) stars of the old, metal-poor globular cluster NGC 6397.

[0910.1086] Massive binaries as the source of abundance anomalies in globular clusters

Tue, 13 Oct 2009 13:22:19 +0200

[0910.1086] Massive binaries as the source of abundance anomalies in globular clusters:

S.E. de Mink, O.R. Pols, N. Langer, R.G. Izzard :: Abundance anomalies observed in globular cluster stars indicate pollution with material processed by hydrogen burning. Two main sources have been suggested: asymptotic giant branch (AGB) stars and massive stars rotating near the break-up limit (spin stars). We propose massive binaries as an alternative source.

[0910.2068] CCD time-series photometry of the globular cluster NGC 5053: RR Lyrae, Blue Stragglers and SX Phoenicis stars revisited

Tue, 13 Oct 2009 13:21:25 +0200

[0910.2068] CCD time-series photometry of the globular cluster NGC 5053: RR Lyrae, Blue Stragglers and SX Phoenicis stars revisited:

A. Arellano Ferro, Sunetra Giridhar, D.M. Bramich :: We report the results of CCD V, r and I time-series photometry of the globular cluster NGC 5053. New times of maximum light are given for the eight known RR Lyrae stars in the field of our images and their periods are revised…

[0910.2049] X-rays from the Eclipsing Millisecond Pulsar PSR J1740-5340 in the Globular Cluster NGC 6397

Tue, 13 Oct 2009 13:19:00 +0200

[0910.2049] X-rays from the Eclipsing Millisecond Pulsar PSR J1740-5340 in the Globular Cluster NGC 6397:

H. H. Huang, W. Becker :: The millisecond pulsar PSR J1740-5340 in the globular cluster NGC 6397 shows radio eclipses over ~40% of its binary orbit. A first Chandra observation revealed indications for the X-ray flux being orbit dependent as well. In this work we analysed five data sets of archival Chandra data taken between 2000 and 2007 in order to investigate the emission across the pulsar’s binary orbit….

[0910.0675] Intrinsic iron spread and a new metallicity scale for Globular Clusters

Tue, 06 Oct 2009 11:48:50 +0200

[0910.0675] Intrinsic iron spread and a new metallicity scale for Globular Clusters:

Eugenio Carretta, Angela Bragaglia, Raffaele Gratton, Valentina D’Orazi, Sara Lucatello :: We have collected spectra of about 2000 red giant branch (RGB) stars in 19 Galactic globular clusters (GC) using FLAMES@VLT (about 100 star with GIRAFFE and about 10 with UVES, respectively, in each GC). These observations provide an unprecedented, precise, and homogeneous data-set of Fe abundances in GCs….

[0910.0310] Globular Cluster Formation Within The Aquarius Simulation

Mon, 05 Oct 2009 15:29:38 +0200

[0910.0310] Globular Cluster Formation Within The Aquarius Simulation:

B. F. Griffen, M. J. Drinkwater, P. A. Thomas, J. C. Helly, K. A. Pimbblet ::The Aquarius project is the first simulation that can resolve the full mass range of potential globular cluster formation sites…

[0909.5265] M22: A [Fe/H] Abundance Range Revealed

Wed, 30 Sep 2009 11:51:00 +0200

[0909.5265] M22: A [Fe/H] Abundance Range Revealed:

G. S. Da Costa, E. V. Held, I. Saviane, M. Gullieuszik :: Intermediate resolution spectra at the Ca II triplet have been obtained for 55 candidate red giants in the field of the globular cluster M22 with the VLT/FORS instrument. Spectra were also obtained for a number of red giants in standard globular clusters to provide a calibration of the observed line strengths with overall abundance [Fe/H] (…) we conclude that, as has long been suspected, M22 is similar to omega Cen in having an intrinsic dispersion in heavy element abundance … If the unusual properties of omega Cen have their origin in a scenario in which the cluster is the remnant nucleus of a disrupted dwarf galaxy, then such a scenario likely applies also to M22.

[0909.5230] Globular Cluster Abundances and What They Can Tell Us About Galaxy Formation

Wed, 30 Sep 2009 11:50:15 +0200

[0909.5230] Globular Cluster Abundances and What They Can Tell Us About Galaxy Formation:

Judith G. Cohen :: We review the properties of globular clusters which make them useful for studying the Galactic halo, Galactic chemical evolution, and the early stages of the formation of the Milky Way…

[0909.1755] A 500 Parsec Halo Surrounding the Galactic Globular NGC 1851

Thu, 10 Sep 2009 16:44:01 +0200

[0909.1755] A 500 Parsec Halo Surrounding the Galactic Globular NGC 1851:

Edward W. Olszewski, Abhijit Saha, Patricia Knezek, Annapurni Subramaniam, Thomas de Boer, Patrick Seitzer :: Using imaging that shows four magnitudes of main sequence stars, we have discovered that the Galactic globular cluster NGC 1851 is surrounded by a halo that is visible from the tidal radius of 700 arcsec (41 pc) to more than 4500 arcsec (>250 pc)….

[0909.1656] Globular clusters in modified Newtonian dynamics: velocity-dispersion profiles from self-consistent models

Thu, 10 Sep 2009 16:43:01 +0200

[0909.1656] Globular clusters in modified Newtonian dynamics: velocity-dispersion profiles from self-consistent models:

A. Sollima, C. Nipoti :: We test the modified Newtonian dynamics (MOND) theory with the velocity-dispersion profiles of Galactic globular clusters populating the outermost region of the Milky Way halo, where the Galactic acceleration is lower than the characteristic MOND acceleration a_0….

[0909.0983] Lithium in the Globular Cluster NGC 6397: Evidence for dependence on evolutionary status

Tue, 08 Sep 2009 16:24:40 +0200

[0909.0983] Lithium in the Globular Cluster NGC 6397: Evidence for dependence on evolutionary status:

J. I. Gonzalez Hernandez et al. :: Most Globular Clusters are believed to host a single stellar populations. They can thus be considered a good place to study the Spite plateau and probe for possible evolutionary modifications of the Li content. We want to determine the Li content of subgiant (SG) and Main Sequence (MS) stars of the old, metal-poor globular cluster NGC 6397… The Li abundance pattern observed in NGC 6397 is different from what is found among field stars, casting some doubt on the use of Globular Cluster stars as representative of Population II with respect to the Li abundance. None of the available theories of Li depletion appears to satisfactorily describe our observations.

[0908.1650] The influence of the C+N+O abundances on the determination of the relative ages of Globular Clusters: the case of NGC 1851 and NGC 6121 (M4)

Thu, 13 Aug 2009 13:30:59 +0200

[0908.1650] The influence of the C+N+O abundances on the determination of the relative ages of Globular Clusters: the case of NGC 1851 and NGC 6121 (M4):

F. D’Antona, P.B. Stetson, P. Ventura, A. Milone, G.P. Piotto, V. Caloi :: The color magnitude diagram (CMD) of NGC 1851 presents two subgiant branches (SGB), probably due the presence of two populations differing in total CNO content. We test the idea that a difference in total CNO may simulate an age difference when comparing the CMD of clusters to derive relative ages. We compare NGC 1851 with NGC 6121 (M4), a cluster of very similar [Fe/H]…

[0907.4974] VERITAS Observations of Globular Clusters

Wed, 29 Jul 2009 12:30:47 +0200

[0907.4974] VERITAS Observations of Globular Clusters:

Michael McCutcheon, for the VERITAS Collaboration :: It has been postulated that globular clusters could be sources of Very-High Energy (VHE) gamma rays, powered by milli-second pulsars. This could be due to cumulative direct emission or to plerion-type emission driven by colliding winds….