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Blue Straggler Stars in Sagittarius Globular Clusters

Blue Straggler Stars in Sagittarius Globular Clusters. Giovanni Carraro, ESO - Chile. Nov 06, 2012. The context:. Sgr offers a different environment to study the BS phenomenon:

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Blue Straggler Stars in Sagittarius Globular Clusters

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  1. Blue Straggler Stars in Sagittarius Globular Clusters Giovanni Carraro, ESO - Chile Nov 06, 2012

  2. The context: • Sgr offers a different environment to study the BS phenomenon: • Star clusters associated with Sgr exhibit wide variations of age, structural and dynamical properties, and metallicity.

  3. The data: BV photometry, Danish telescope @LaSilla

  4. The Color-Magnitude Diagrams: Arp 2 and Terzan 8 are Sgrgenuine members, NGC 5634 and Palomar 12 are stripped clusters, now floating in the MW halo.

  5. Structural properties:

  6. Structural properties: cont. Sgr main body clusters

  7. BS stars selection: Contamination taken into account in a statistical way

  8. BS radial distribution: Not segregated Segregated Segregated Not segregated

  9. BS specific frequency: Sgr Main Body contamination ????

  10. BS cumulative distribution: 60 % 0.4 % 44 % 75% Anderson-Darling test

  11. Conclusions: • The main idea of this study was to use BS as test-particle to probe the parent cluster dynamical status; • Their distribution nicely correlates with the King parameters of the parent clusters; • Special care must be taken since contamination from Sgr Main Body can complicate significantly the interpretation.

  12. BS in Galactic Old Open Clusters • Open clusters seem to possess the largest frequency of BS (see Yazan talk) • There is a trend of having more BS at decreasing total luminosity and increasing age (De Marchi et al. 2006) • Membership is a challenge (see Javier talk)

  13. BS in Galactic Old Open Clusters Carraro, Boffin, Ahumada, Beccari, Davies, Monaco

  14. BS in Galactic Old Open Clusters

  15. BS in Galactic Old Open Clusters • FLAMES (blue setup) + UVES • Multi-epoch ( typically 3 epochs) • Improving membership, improving statististics, finding pathological cases • In the middle between micro- and macro-economy

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