More Like this

1. The Open Cluster Chemical Abundances and Mapping Survey. II. Precision Cluster Abundances for APOGEE Using SDSS DR14

   https://doi.org/10.3847/1538-3881/aad635  

   Donor, John ; Frinchaboy, Peter M. ; Cunha, Katia ; Thompson, Benjamin ; O’Connell, Julia ; Zasowski, Gail ; Jackson, Kelly M. ; McGrath, Brianne Meyer ; Almeida, Andrés ; Bizyaev, Dmitry ; et al ( October 2018 , The Astronomical Journal)
2. The Open Cluster Chemical Abundances and Mapping Survey. V. Chemical Abundances of CTIO/Hydra Clusters Using The Cannon

   https://doi.org/10.3847/1538-3881/ac5835  

   Ray, Amy E. ; Frinchaboy, Peter M. ; Donor, John ; Chojnowski, S. D. ; Melendez, Matthew ( April 2022 , The Astronomical Journal)

   Open clusters are key chemical and age tracers of Milky Way evolution. While open clusters provide significant constraints on galaxy evolution, their use has been limited due to discrepancies in measuring abundances from different studies. We analyze medium-resolution (R∼ 19,000) Cerro Tololo Inter-American Observatory/Hydra spectra of giant stars in 58 open clusters using The Cannon to determine [Fe/H], [Mg/Fe], [Si/Fe], [Al/Fe], and [O/Fe]. This work adds an additional 55 primarily southern hemisphere open clusters calibrated to the Sloan Digital Sky Survey/Apache Point Observatory Galactic Evolution Experiment DR16 metallicity system. This uniform analysis is compared to previous studies [Fe/H] measurements for 23 clusters and we present spectroscopic metallicities for the first time for 35 open clusters.

    

   more » « less
3. WIYN Open Cluster Study 89. M48 (NGC 2548) 2: Lithium Abundances in the 420 Myr Open Cluster M48 from Giants through K Dwarfs* †

   https://doi.org/10.3847/1538-4357/acc5e3  

   Sun, Qinghui ; Deliyannis, Constantine P. ; Steinhauer, Aaron ; Anthony-Twarog, Barbara J. ; Twarog, Bruce A. ( July 2023 , The Astrophysical Journal)

   We consider WIYN/Hydra spectra of 329 photometric candidate members of the 420 Myr old open cluster M48 and report lithium detections or upper limits for 234 members and likely members. The 171 single members define a number of notable Li-mass trends, some delineated even more clearly than in Hyades/Praesepe: the giants are consistent with subgiant Li dilution and prior MS Li depletion due to rotational mixing. A dwarfs (8600–7700 K) have upper limits higher than the presumed initial cluster Li abundance. Two of five late A dwarfs (7700–7200 K) are Li-rich, possibly due to diffusion, planetesimal accretion, and/or engulfment of hydrogen-poor planets. Early F dwarfs already show evidence of Li depletion seen in older clusters. The Li–T_efftrends of the Li Dip (6675–6200 K), Li Plateau (6200–6000 K), and G and K dwarfs (6000–4000 K) are very clearly delineated and are intermediate to those of the 120 Myr old Pleiades and 650 Myr old Hyades/Praesepe, which suggests a sequence of Li depletion with age. The cool side of the Li Dip is especially well defined with little scatter. The Li–T_efftrend is very tight in the Li Plateau and early G dwarfs, but scatter increases gradually for cooler dwarfs. These patterns support and constrain models of the universally dominant Li depletion mechanism for FGK dwarfs, namely rotational mixing due to angular momentum loss; we discuss how diffusion and gravity-wave-driven mixing may also play roles. For late G/K dwarfs, faster rotators show higher Li than slower rotators, and we discuss possible connections between angular momentum loss and Li depletion.

    

   more » « less
4. The Gaia -ESO Survey: a new approach to chemically characterising young open clusters: II. Abundances of the neutron-capture elements Cu, Sr, Y, Zr, Ba, La, and Ce

   https://doi.org/10.1051/0004-6361/202141069  

   Baratella, M. ; D’Orazi, V. ; Sheminova, V. ; Spina, L. ; Carraro, G. ; Gratton, R. ; Magrini, L. ; Randich, S. ; Lugaro, M. ; Pignatari, M. ; et al ( September 2021 , Astronomy & Astrophysics)

   null (Ed.)

   Context. Young open clusters (ages of less than 200 Myr) have been observed to exhibit several peculiarities in their chemical compositions. These anomalies include a slightly sub-solar iron content, super-solar abundances of some atomic species (e.g. ionised chromium), and atypical enhancements of [Ba/Fe], with values up to ~0.7 dex. Regarding the behaviour of the other s -process elements like yttrium, zirconium, lanthanum, and cerium, there is general disagreement in the literature: some authors claim that they follow the same trend as barium, while others find solar abundances at all ages. Aims. In this work we expand upon our previous analysis of a sample of five young open clusters (IC 2391, IC 2602, IC 4665, NGC 2516, and NGC 2547) and one star-forming region (NGC 2264), with the aim of determining abundances of different neutron-capture elements, mainly Cu  I , Sr  I , Sr  II , Y  II , Zr  II , Ba  II , La  II , and Ce  II . For NGC 2264 and NGC 2547 we present the measurements of these elements for the first time. Methods. We analysed high-resolution, high signal-to-noise spectra of 23 solar-type stars observed within the Gaia -ESO survey. After a careful selection, we derived abundances of isolated and clean lines via spectral synthesis computations and in a strictly differential way with respect to the Sun. Results. We find that our clusters have solar [Cu/Fe] within the uncertainties, while we confirm that [Ba/Fe] is super-solar, with values ranging from +0.22 to +0.64 dex. Our analysis also points to a mild enhancement of Y, with [Y/Fe] ratios covering values between 0 and +0.3 dex. For the other s -process elements we find that [X/Fe] ratios are solar at all ages. Conclusions. It is not possible to reconcile the anomalous behaviour of Ba and Y at young ages with standard stellar yields and Galactic chemical evolution model predictions. We explore different possible scenarios related to the behaviour of spectral lines, from the dependence on the different ionisation stages and the sensitivity to the presence of magnetic fields (through the Landé factor) to the first ionisation potential effect. We also investigate the possibility that they may arise from alterations of the structure of the stellar photosphere due to the increased levels of stellar activity that affect the spectral line formation, and consequently the derived abundances. These effects seem to be stronger in stars at ages of less than ~ 100 Myr. However, we are still unable to explain these enhancements, and the Ba puzzle remains unsolved. With the present study we suggest that other elements, for example Sr, Zr, La, and Ce, might be more reliable tracer of the s -process at young ages, and we strongly encourage further critical observations. 

   more » « less
5. Chemical Abundances of Main-sequence, Turnoff, Subgiant, and Red Giant Stars from APOGEE Spectra. I. Signatures of Diffusion in the Open Cluster M67

   https://doi.org/10.3847/1538-4357/aab612  

   Souto, Diogo ; Cunha, Katia ; Smith, Verne V. ; Prieto, C. Allende ; García-Hernández, D. A. ; Pinsonneault, Marc ; Holzer, Parker ; Frinchaboy, Peter ; Holtzman, Jon ; Johnson, J. A. ; et al ( April 2018 , The Astrophysical Journal)