Blue Straggler Stars: The Spectacular Population in M80

Ferraro, F. R.; Paltrinieri, B.; Rood, Robert T.; Dorman, Ben

doi:10.1086/307700

Cited by 131 publications

(200 citation statements)

References 21 publications

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“…To minimize incompleteness effects in the ground-based observations of the crowded central regions of the cluster, while still taking advantage of the superior capability of UV observations in detecting the BSSs (Ferraro et al 1999b(Ferraro et al , 2001), we divided the data set in two main samples. The HST sample includes only stars in the WFPC2 and complementary ACS catalogs.…”

Section: Astrometry Photometric Calibration and Sample Definitionmentioning

confidence: 99%

“…In order to clearly show the difference between clusters with BTs populated up to the EHB region and clusters with BHk stars, UV photometry is essential. In Figure 5 we compare the (m 255 , m 255 À U ) CMDs of NGC 6388 to that of M80 (Ferraro et al 1997(Ferraro et al , 1999b. We chose M80 because among the clusters for which we have a full range of data, it is the one with the HB extending to the highest T eA .…”

Section: The Hst Samplementioning

confidence: 99%

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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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Section: Astrometry Photometric Calibration and Sample Definitionmentioning

confidence: 99%

Section: The Hst Samplementioning

confidence: 99%

Blue Straggler Stars in the Unusual Globular Cluster NGC 63881

Dalessandro

Lanzoni

Ferraro

et al. 2008

ApJ

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“…Hence the combination of high angular resolution and UV imaging capabilities (as offered by the HST) is the only solution to significantly reduce the level of crowding and acquire complete samples of BSSs even in the core of highly concentrated GCs. Within this framework, approximately 20 years ago we promoted the so-called UV route to the study of BSSs in GCs (see Ferraro et al 1997Ferraro et al , 1999Ferraro et al , 2001Ferraro et al , 2003, an approach that allowed us to derive complete samples of BSSs in several Galactic GCs (GGCs), including systems of very high central density (see Lanzoni et al 2007a,b,c;Dalessandro et al 2008Dalessandro et al , 2009Sanna et al 2012Sanna et al , 2014Contreras Ramos et al 2012). …”

Section: Introductionmentioning

confidence: 99%

The “UV-route” to Search for Blue Straggler Stars in Globular Clusters: First Results from the HST UV Legacy Survey

Raso

Ferraro

Dalessandro

et al. 2017

ApJ

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We used data from the HST UV Legacy Survey of Galactic Globular Clusters to select the Blue Straggler Star (BSS) population in four intermediate/high density systems (namely NGC 2808, NGC 6388, NGC 6541 and NGC 7078) through a "UV-guided search". This procedure consists in using the F275W images in each cluster to construct the master list of detected sources, and then force it to the images acquired in the other filters. Such an approach optimizes the detection of relatively hot stars and allows the detection of complete sample of BSSs even in the central region of high-density clusters, because the light from the bright cool giants, which dominates the optical emission in old stellar systems, is sensibly reduced at UV wavelengths. Our UV-guided selections of BSSs have been compared to the samples obtained in previous, optical-driven surveys, clearly demonstrating the efficiency of the UV approach. In each cluster we also measured the parameter A + , defined as the area enclosed between the cumulative radial distribution of BSSs and that of a reference population, which traces the level of BSS central segregation and the level of dynamical evolution suffered by the system. The values measured for the four clusters studied in this paper nicely fall along the dynamical sequence recently presented for a sample of 25 clusters.

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“…Ferraro et al (1997b) provide some evidence that the radial distribution of ER stars in M3 parallels that of the stragglers. Ferraro et al (1999b) find that the cumulative radial distribution of the ER HB stars parallels that of the blue stragglers, and both are more centrally concentrated than the combined RGB and HB sample. For M5, we find that the cumulative radial distribution of the two groups of ER HB stars is actually less concentrated than the HB stars ( Fig.…”

Section: Unusual Hb Starsmentioning

confidence: 71%

Exploring the Upper Red Giant and Asymptotic Giant Branches: The Globular Cluster M5

Sandquist

Bolte

2004

ApJ

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We have tabulated lists of upper red giant, horizontal-, and asymptotic giant branch (RGB, HB, and AGB) stars in the globular cluster M5 that are complete to over 10 0 from the core for the RGB and AGB samples, and 8 0 for the HB sample. The large samples give us the most precise value of R 2 ¼ N AGB =N HB to date for a single globular cluster (0:176 AE 0:018). This is incompatible with theoretical calculations using the most recent physical inputs. The discrepancy can probably be attributed to the dependence of observed R 2 values on HB morphology. We identify the cluster M55 as another possible example of this effect. Samples of HB and AGB stars in populous clusters may provide a means of calibrating the masses of HB stars in globular clusters. The cumulative luminosity function of the upper RGB shows an apparent deficit of observed stars near the tip of the branch. This feature has less than a 2% chance of being due to statistical fluctuations. The slope of the cumulative luminosity function for AGB stars is consistent with the theoretically predicted value from stellar models when measurement bias is taken into account. We also introduce a new diagnostic R clump that reflects the fraction of the AGB lifetime that a star spends in the AGB clump. For M5 we find R clump ¼ 0:42 AE 0:05, in marginal disagreement with theoretical predictions. Finally, we note that the blue half of M5's instability strip (where first-overtone RR Lyrae stars reside) is underpopulated, based on the large numbers of fundamental mode RR Lyrae stars and on the nonvariable stars at the blue end of the instability strip. This fact may imply that the evolutionary tracks (and particularly the colors) of stars in the instability strip are affected by pulsations.

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Blue Straggler Stars: The Spectacular Population in M80

Cited by 131 publications

References 21 publications

Blue Straggler Stars in the Unusual Globular Cluster NGC 63881

Blue Straggler Stars in the Unusual Globular Cluster NGC 63881

The “UV-route” to Search for Blue Straggler Stars in Globular Clusters: First Results from the HST UV Legacy Survey

Exploring the Upper Red Giant and Asymptotic Giant Branches: The Globular Cluster M5

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