WIYN open cluster study: The old open cluster, NGC 188, and a re-evaluation of Lithium-richness among red giants

• DOI: 10.1093/mnras/stac1251
• Publication Date: 2022-05-06T11:34:53Z
• Authors: Qinghui Sun; Constantine P Del...; Bruce A Twarog; Barbara J Anthony...; Jeffrey D Cummings; Aaron Steinhauer
• Keywords: Red-giant branch

We present WIYN/Hydra spectra of 34 red giant candidate members NGC 188, which, together with WOCS and Gaia data yield 23 single members, 6 binary 4 nonmembers, 1 nonmember. report [Fe/H] for 29 derive [Fe/H]$_{\rm{NGC188}}$ = +0.064 $\pm$ 0.018 dex ($\sigma_{\mu}$) (sky A(Fe)$_{\odot}$ 7.520 0.015 ($\sigma_{\mu}$)). discuss effects on the derived parameters varying Yale-Yonsei isochrones to fit turnoff. take advantage coolest, lowest-gravity giants refine line list near Li 6707.8 \AA. Using synthesis we detections A(Li) 1.17, 1.65, 2.04, 0.60 stars 4346, 4705, 5027, 6353, respectively, 3$\sigma$ upper-limits other members. Whereas only two meet traditional criterion "Li-richness" > 1.5 dex, argue that since cluster vanish as subgiants evolve base RGB, all four are Li-rich in this cluster's context. An incidence even a few sample is far higher than what recent large surveys have found field. All lie either slightly or substantially away from fiducial sequence, possibly providing clues about their Li-richness. number possibilities origin each star, suggest potentially discriminating future observations.