Another Nonsegregated Blue Straggler Population in a Globular Cluster: the Case of NGC 2419

Dalessandro, E.; Lanzoni, B.; Ferraro, F. R.; Vespe, F.; Bellazzini, M.; Rood, Robert T.

doi:10.1086/588462

Cited by 95 publications

(103 citation statements)

References 50 publications

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“…Table 4 lists the values of Γ MST and the related 1σ uncertainties computed for the BSS populations in the four target clusters, and, for comparison, for NGC 2419 and Pal 14. In agreement with the results of Dalessandro et al (2008) and Beccari et al (2011), we find that BSS and RGB stars share the same radial distribution in NGC 2419 and Pal 14 (Γ MST 1). Conversely, BSSs appear to be significantly more segregated than giant stars in the other four GCs.…”

Section: The Minimum Spanning Treesupporting

confidence: 92%

The Central Blue Straggler Population in Four Outer-Halo Globular Clusters

Beccari

Lützgendorf

Olczak

et al. 2012

ApJ

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Using Hubble Space Telescope/Wide Field Planetary Camera 2 data, we have performed a comparative study of the Blue Straggler Star (BSS) populations in the central regions of the globular clusters (GCs) AM 1, Eridanus, Palomar 3, and Palomar 4. Located at distances R GC > 50 kpc from the Galactic center, these are (together with Palomar 14 and NGC 2419) the most distant clusters in the halo. We determine their color-magnitude diagrams and centers of gravity. The four clusters turn out to have similar ages (10.5-11 Gyr), significantly smaller than those of the inner-halo globulars, and similar metallicities. By exploiting wide-field ground-based data, we build the most extended radial density profiles from resolved star counts ever published for these systems. These are well reproduced by isotropic King models of relatively low concentration. BSSs appear to be significantly more centrally segregated than red giants in all GCs, in agreement with the estimated core and half-mass relaxation times which are smaller than the cluster ages. Assuming that this is a signature of mass segregation, we conclude that AM 1 and Eridanus are slightly dynamically more evolved than Pal 3 and Pal 4.

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Section: The Minimum Spanning Treesupporting

confidence: 92%

The Central Blue Straggler Population in Four Outer-Halo Globular Clusters

Beccari

Lützgendorf

Olczak

et al. 2012

ApJ

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“…In a few other GCs (see, for example, NGC 1904 and M75;Lanzoni et al 2007b;Contreras Ramos et al 2012, respectively) the radial distribution shows a clear central peak but no upturn in the external cluster regions. In the case of ω Centauri (Ferraro et al 2006b), NGC 2419 (Dalessandro et al 2008), and Palomar 14 ) the BSS radial distribution is flat all over the entire cluster extension. Since BSSs are more massive than the average cluster stars (and therefore suffer from the effects of dynamical friction), these different observed shapes have been interpreted as due to different "dynamical ages" of the host clusters (Ferraro et al 2012, hereafter F12): a flat BSS distribution is found in dynamically young GCs (Family I), where two-body relaxation has been ineffective in establishing energy equipartition in a Hubble time and dynamical friction has not segregated the BSS population yet.…”

Section: Introductionmentioning

confidence: 91%

Deep Multi-Telescope Photometry of NGC 5466. I. Blue Stragglers and Binary Systems

Beccari

Dalessandro²,

Lanzoni³

et al. 2013

ApJ

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We present a detailed investigation of the radial distribution of blue straggler star (BSS) and binary populations in the Galactic globular cluster NGC 5466, over the entire extension of the system. We used a combination of data acquired with the Advanced Camera for Survey on board the Hubble Space Telescope, the LBC-blue mounted on the Large Binocular Telescope, and MEGACAM on the Canada-France-Hawaii Telescope. BSSs show a bimodal distribution with a mild central peak and a quite internal minimum. This feature is interpreted in terms of a relatively young dynamical age in the framework of the "dynamical clock" concept proposed by Ferraro et al. The estimated fraction of binaries is ∼6%-7% in the central region (r < 90 ) and slightly lower (∼5.5%) in the outskirts, at r > 200 . Quite interestingly, the comparison with the results of Milone et al. suggests that binary systems may also display a bimodal radial distribution, with the position of the minimum consistent with that of BSSs. If confirmed, this feature would give additional support to the scenario where the radial distribution of objects more massive than the average cluster stars is primarily shaped by the effect of dynamical friction. Moreover, this would also be consistent with the idea that the unperturbed evolution of primordial binaries could be the dominant BSS formation process in low-density environments.

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“…The standard photometric analysis (see Dalessandro et al 2008aDalessandro et al , 2008b) has been performed on the "flt" images, which are corrected for flat field, bias, and dark counts. These images have been further corrected for "Pixel-area-map" 6 with standard IRAF procedures.…”

Section: Observations and Data Analysismentioning

confidence: 99%

OPTICAL IDENTIFICATION OF He WHITE DWARFS ORBITING FOUR MILLISECOND PULSARS IN THE GLOBULAR CLUSTER 47 TUCANAE

Cadelano

Pallanca

Ferraro

et al. 2015

ApJ

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We used ultra-deep UV observations obtained with the Hubble Space Telescope to search for optical companions to binary millisecond pulsars (MSPs) in the globular cluster 47 Tucanae. We identified four new counterparts (to MSPs 47TucQ, 47TucS, 47TucT, and 47TucY) and confirmed those already known (to MSPs 47TucU and 47TucW). In the color-magnitude diagram, the detected companions are located in a region between the main sequence and the CO white dwarf (WD) cooling sequences, consistent with the cooling tracks of He WDs with masses between 0.15 M e and 0.20 M e . For each identified companion, mass, cooling age, temperature, and pulsar mass (as a function of the inclination angle) have been derived and discussed. For 47TucU we also found that the past accretion history likely proceeded at a sub-Eddington rate. The companion to the redback 47TucW is confirmed to be a non-degenerate star, with properties particularly similar to those observed for black widow systems. Two stars have been identified within the 2σ astrometric uncertainty from the radio positions of 47TucH and 47TucI, but the available data prevent us from firmly assessing whether they are the true companions of these two MSPs.

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Another Nonsegregated Blue Straggler Population in a Globular Cluster: the Case of NGC 2419

Cited by 95 publications

References 50 publications

The Central Blue Straggler Population in Four Outer-Halo Globular Clusters

The Central Blue Straggler Population in Four Outer-Halo Globular Clusters

Deep Multi-Telescope Photometry of NGC 5466. I. Blue Stragglers and Binary Systems

OPTICAL IDENTIFICATION OF He WHITE DWARFS ORBITING FOUR MILLISECOND PULSARS IN THE GLOBULAR CLUSTER 47 TUCANAE

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