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1. Stellar Radial Velocities in the Old Open Cluster M67 (NGC 2682). II. The Spectroscopic Binary Population

   https://doi.org/10.3847/1538-3881/abdd23  

   Geller, Aaron M.; Mathieu, Robert D.; Latham, David W.; Pollack, Maxwell; Torres, Guillermo; Leiner, Emily M. (March 2021, The Astronomical Journal)

   null (Ed.)
2. Double degenerate candidates in the open cluster NGC 6633

   https://doi.org/10.1017/S1743921320001040  

   Barnett, Joseph W.; Williams, Kurtis A. (October 2019, Proceedings of the International Astronomical Union)

   null (Ed.)

   Abstract The study of white dwarfs, the end stage of stellar evolution for more than 95% of stars, is critical to bettering our understanding of the late stages of the lives of low mass stars. In particular, the post main sequence evolution of binary star systems is complex, and the identification and analysis of double degenerate systems is a crucial step in constraining models of binary star systems. Binary white dwarfs in open star clusters are particularly useful because cluster parameters such as distance, metal content, and total system age are more tightly constrained than for field double degenerates. Here we use the precision astrometry from the Gaia Data Release 2 catalog to study two other white dwarfs which were identified as candidate double degenerates in the field of the open star cluster NGC 6633. One of the two objects, LAWDS 4, is found to have astrometric properties fully consistent with that of the cluster. In such a case, the object is significantly overluminous for a single white dwarf, strongly indicating binarity. The second candidate binary, LAWDS 7, appears to be inconsistent with cluster membership, though a more thorough analysis is necessary to properly quantify the probability. At present we are proceeding to model the photometric and spectroscopic data for both objects as if they were cluster member double degenerates. Results of this latter analysis are forthcoming. Our results will add crucial data to the study of binary star evolution in open star clusters. 

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3. Interstellar Polarization and Extinction towards the Open Cluster NGC 457

   https://doi.org/10.1088/1538-3873/aa7f6c  

   Topasna, Gregory A.; Daman, Eryn A.; Kaltcheva, Nadia T. (October 2017, Publications of the Astronomical Society of the Pacific)
4. WIYN Open Cluster Study. LXXXII. Radial-velocity Measurements and Spectroscopic Binary Orbits in the Open Cluster NGC 7789

   https://doi.org/10.3847/1538-3881/abad3b  

   Nine, Andrew C.; Milliman, Katelyn E.; Mathieu, Robert D.; Geller, Aaron M.; Leiner, Emily M.; Platais, Imants; Tofflemire, Benjamin M. (October 2020, The Astronomical Journal)

   null (Ed.)
5. WIYN open cluster study: The old open cluster, NGC 188, and a re-evaluation of Lithium-richness among red giants

   https://doi.org/10.1093/mnras/stac1251  

   Sun, Qinghui; Deliyannis, Constantine P.; Twarog, Bruce A.; Anthony-Twarog, Barbara J.; Cummings, Jeffrey D.; Steinhauer, Aaron (May 2022, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We present WIYN1/Hydra spectra of 34 red giant candidate members of NGC 188, which, together with WOCS2 and Gaia data yield 23 single members, 6 binary members, 4 single non-members, and 1 binary non-member. We report [Fe/H] for 29 members and derive [Fe/H]NGC188  = +0.064 ± 0.018 dex (σμ) (sky spectra yield A(Fe)⊙  = 7.520 ± 0.015 dex (σμ)). We discuss effects on the derived parameters of varying Yale-Yonsei isochrones to fit the turnoff. We take advantage of the coolest, lowest gravity giants to refine the line list near Li 6707.8 Å. Using synthesis we derive detections of A(Li)3  = 1.17, 1.65, 2.04, and 0.60 dex for stars 4346, 4705, 5027, and 6353, respectively, and 3σ upper limits for the other members. Whereas only two of the detections meet the traditional criterion for ‘Li-richness’ of A(Li) > 1.5 dex, we argue that since the cluster A(Li) vanish as subgiants evolve to the base of the RGB, all four stars are Li-rich in this cluster’s context. An incidence of even a few Li-rich stars in a sample of 29 stars is far higher than what recent large surveys have found in the field. All four stars lie either slightly or substantially away from the cluster fiducial sequence, possibly providing clues about their Li-richness. We discuss a number of possibilities for the origin for the Li in each star, and suggest potentially discriminating future observations. 

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