NOAO >   Observing Info >   Approved Programs >   2019B-0506

Small NOAO Logo

Program Information for 2019B-0506


PI: Robert Mathieu, U. of Wisconsin, Madison, mathieu@astro.wisc.edu
Address: Department of Astronomy, 475 N. Charter St., Madison, WI 53706 United States

CoI: Andrew Nine, U. of Wisconsin, Madison
CoI: Meng Sun, U. of Wisconsin, Madison
CoI: Rachel McLure, U. of Wisconsin, Madison
CoI: Evan Linck, U. of Wisconsin, Madison
CoI: Ryan Drake, U. of Wisconsin, Madison
CoI: David Szymulewski, U. of Wisconsin, Madison

Title: A Study of Binary Populations and Alternative Pathways of Stellar Evolution in Open Clusters

Abstract: Approximately 25% of all evolved stars in old open star clusters are not on single-star evolutionary paths. These blue stragglers (BSs), sub-subgiants (SSGs), yellow giants, and our newly discovered "blue lurkers", have been an enduring challenge for stellar evolution theory. It is now clear that these are stars on alternative evolutionary pathways within the large binary-star population of solar-type stars. We have an ongoing study to probe the nature of these alternative pathways, which has involved a wide array of observing facilities on the ground and in space. The foundation for all of the work are WIYN/MOS high-precision radial-velocity measurements. Here we propose RV measurements of these stars and the binary populations in two intermediate-age open clusters of similar richness: NGC 7789 (1.8 Gyr) and NGC 2506 (2.1 Gyr). Notably, NGC 2506 has 10 BSs, while NGC 7789 has at least 27. Our observations will provide cluster membership and binary orbital properties for these BSs, as well as identify possible SSG RV members. Our observations will also establish the hard-binary fraction and frequency distributions of orbital parameters (periods, eccentricities, secondary mass distributions, etc.) in these clusters, establishing the stellar dynamical factors that may influence the frequency of stars on these pathways. In addition, we will move onto the main-sequence in the very old Kepler-field cluster NGC 6791 in order to discover a second population of blue lurkers. These data will be the touchstones for detailed binary evolution modeling and N-body open cluster simulations. Combining the observed populations and the theoretical models will shed light on these alternative stellar evolution pathways and the relative production rates within an ever growing variety of formation channels.

Program Type: WTAC

Scheduled Nights:
Run 1 (2019B):  WIYN/HYDR -- 6n on Sep 16 - Sep 21 2019
Run 2 (2019B):  WIYN/HYDR -- 5n on Dec 17 - Dec 18 2019, Jan 05 - Jan 07 2020


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



NOAO >   Observing Info >   Approved Programs >   2019B-0506

noaoprop-help@noao.edu

Small NOAO Logo