Blue Stragglers, Young White Dwarfs, and UV‐Excess Stars in the Core of 47 Tucanae

Ferraro, F. R.; D’Amico, N.; Possenti, A.; Mignani, Roberto; Paltrinieri, B.

doi:10.1086/322773

Cited by 97 publications

(129 citation statements)

References 39 publications

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“…In particular, we have studied the potential NF population in 47 Tuc, which is both less dense and more massive than NGC 6397, and for which a wealth of observational data is becoming available. In this Ferraro et al (2001aFerraro et al ( , 2001b. Open circles and triangles denote blue stragglers and normal white dwarfs, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…In what follows, we discuss our expectations for the (currently undetected) NF population in 47 Tuc. The attraction of this cluster is the rich data set spanning X-ray (Grindlay et al 2001a), UV (Ferraro et al 2001b;Knigge et al 2002), optical (Gilliland et al 2000), and radio (Camilo et al 2000) wavelengths. 47 Tuc is also interesting in that it is a dense, pre-core-collapse cluster and somewhat more massive than NGC 6397.…”

Section: Application To 47 Tucmentioning

confidence: 99%

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Helium Core White Dwarfs in Globular Clusters

Hansen

Kalogera

Rasio

2003

ApJ

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We examine the theoretical implications of a population of low-mass helium core white dwarfs in globular clusters. In particular, we focus on the observed population in the core of NGC 6397, where several low-mass white dwarf candidates have been identified as '' nonflickerers '' by Cool and collaborators. Age and mass estimates from cooling models, combined with dynamical and evolutionary considerations, lead us to infer that the dark binary companions are C/O white dwarfs rather than neutron stars. Furthermore, we find that the progenitor binaries very likely underwent an exchange interaction within the last 10 9 yr. We examine the prospects for detecting a similar population in other globular clusters, with particular attention to the case of 47 Tuc.

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Section: Discussionmentioning

confidence: 99%

Section: Application To 47 Tucmentioning

confidence: 99%

Helium Core White Dwarfs in Globular Clusters

Hansen

Kalogera

Rasio

2003

ApJ

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“…Using the procedure described in Ferraro et al (2001Ferraro et al ( , 2003) the WFI catalog has been placed on the absolute astrometric system. The eight WFI CCDs have been astrometrized by crosscorrelating each of them with the new astrometric Two Micron All Sky Survey (2MASS) catalog using a specific tool developed at Bologna Observatory.…”

Section: Astrometry Photometric Calibration and Sample Definitionmentioning

confidence: 99%

“…At the end of the procedure the rms residuals (which we take as representative of the astrometric accuracy) were of the order of $0.3 00 both in right ascension and declination. By using the procedure described in Ferraro et al (1997Ferraro et al ( , 2001), the photometric calibration of the UV magnitudes (F255W and F336W ) has been performed in the STmag system, adopting the Holtzman et al (1995) zero points. The optical (B and V ) magnitudes have been transformed to the Johnson system by using the stars in common with the catalog of Piotto et al (2002).…”

Section: Astrometry Photometric Calibration and Sample Definitionmentioning

confidence: 99%

Blue Straggler Stars in the Unusual Globular Cluster NGC 63881

Dalessandro

Lanzoni

Ferraro

et al. 2008

ApJ

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We have used multiband high-resolution HST WFPC2 and ACS observations combined with wide-field groundbased observations to study the blue straggler star (BSS) population in the Galactic globular cluster NGC 6388. As in several other clusters we have studied, the BSS distribution is found to be bimodal: highly peaked in the cluster center, rapidly decreasing at intermediate radii, and rising again at larger radii. In other clusters the sparsely populated intermediateradius region (or ''zone of avoidance'') corresponds well to that part of the cluster where dynamical friction would have caused the more massive BSSs or their binary progenitors to settle to the cluster center. Instead, in NGC 6388, BSSs still populate a region that should have been cleaned out by dynamical friction effects, thus suggesting that dynamical friction is somehow less efficient than expected. As a by-product of these observations, the peculiar morphology of the horizontal branch (HB) is also confirmed. In particular, within the (very extended ) blue portion of the HB we are able to clearly characterize three subpopulations: ordinary blue HB stars, extreme HB stars, and blue hook stars. Each of these populations has a radial distribution which is indistinguishable from normal cluster stars.

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“…The first evidence of the presence of a BSS bimodal distribution (Ferraro et al 1997) was found in M 3 and was later on confirmed for other clusters: M 55 (Zaggia et al 1997); 47 Tuc (Ferraro et al 2001); Pal 13 (Clark et al 2004); NGC 6752 (Sabbi et al 2004); M 5 (Warren et al 2006); and M 62 (Beccari et al 2006), while in ω Cen the bimodality seems to be ruled out .…”

Section: Article Published By Edp Sciencesmentioning

confidence: 79%

Environmental Effects on the Globular Cluster Blue Straggler Population: a Statistical Approach

Moretti

Angeli

Piotto³

2007

Proc. IAU

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Context. Blue stragglers stars (BSS) constitute an ubiquitous population of objects whose origin involves both dynamical and stellar evolution. Aims. In this paper we study the properties of a catalogue of BSS extracted from an homogeneous sample of 56 Galactic globular clusters (GC) observed with Wide-Field Planetary Camera 2 on board of Hubble Space Telescope (WFPC2/HST). Methods. With the purpose of investigating the environmental dependence of the BSS formation mechanisms, we explore possible monovariate relations between the frequency of BSS (divided in different subsamples according to their location with respect to the parent cluster core radius and half-mass radius) and the main parameters of their host GC. We also performed a principal component analysis (PCA) to extract the main parent cluster parameters, which characterise the BSS family. Results. We find that any subpopulation of BSS strongly depends on the luminosity of the cluster, on the extension of the cluster horizontal branch, and on the central velocity dispersion: more luminous clusters and clusters with a smaller central velocity dispersion have a higher BSS frequency. Moreover, we find that clusters having higher mass, higher central densities, and smaller core relaxation timescales have, on average, more luminous BSS. Finally, different dependencies seem to hold for clusters with different integrated luminosity: brighter clusters show a BSS population that depends on the collisional parameter, while BSS in fainter clusters are mostly influenced by the cluster luminosity and the dynamical timescales.

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Blue Stragglers, Young White Dwarfs, and UV‐Excess Stars in the Core of 47 Tucanae

Cited by 97 publications

References 39 publications

Helium Core White Dwarfs in Globular Clusters

Helium Core White Dwarfs in Globular Clusters

Blue Straggler Stars in the Unusual Globular Cluster NGC 63881

Environmental Effects on the Globular Cluster Blue Straggler Population: a Statistical Approach

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