NOAO >   Observing Info >   Approved Programs >   2015B-0803

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Program Information for 2015B-0803


PI: Katelyn E Milliman, U. of Wisconsin, Madison, milliman@astro.wisc.edu
Address: Astronomy Department, 475 N. Charter Street, Madison, Wisconsin 53706 USA

CoI: Robert D Mathieu, U. of Wisconsin, Madison
CoI: Simon Schuler, University of Tampa

Title: Surface Abundances of Blue Stragglers in NGC 7789

Abstract: We propose to measure the surface abundances of barium for the blue stragglers in the intermediate-aged open cluster NGC 7789. This will allow us to determine their origins and distinguish between the different theoretical models of blue straggler formation. Blue stragglers resulting from stellar collisions of main-sequence stars are expected to retain roughly the same surface abundance as the more massive star in the collision. On the other hand, blue stragglers formed by mass transfer from an AGB companion will have a surface abundance altered by the nucleosynthesis that occurred within the AGB donor star. The enhancement of the $s$-process element barium has been detected in almost half of the blue stragglers measured in the intermediate-aged open cluster NGC 6819, but not in the BSs of the older open clusters, M67 and NGC 188. Exploring more intermediate-aged clusters is vital to understanding these differences and for understanding blue straggler formation in open clusters environments.

Program Type: WTAC

Scheduled Nights:
Run 1 (2015B):  WIYN/HYDR -- 1n on Sep 12 2015
Run 2 (2015B):  WIYN/HYDR -- 1n on Sep 13 2015


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NOAO >   Observing Info >   Approved Programs >   2015B-0803

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