Abundâncias químicas em estrelas anãs FGK do aglomerado aberto das Plêiades a partir de espectros APOGEE

Abstract

Open clusters are essential for understanding stellar chemistry and the internal physical processes that occur during stellar evolution, which can alter chemical homogeneity. In this context, we utilized the latest data from the OCCAM project to identify open clusters that may or may not exhibit evidence of atomic diffusion. Atomic diffusion describes gravitational atomic-scale transport occurring in the stellar atmosphere, influenced primarily by stellar age and metallicity. Our analysis identified the clusters NGC 2682, NGC 188, NGC 752, NGC 6811, and NGC 2632 as potential candidates to show signs of atomic diffusion. Conversely, the clusters NGC 7789, Ruprecht 147, NGC 6866, Melotte 22, Melotte 20, ASCC 16, ASCC 19, ASCC 21, and Collinder 69 do not exhibit such signs. This study focuses on the open cluster of the Pleiades, Melotte 22, demonstrating that atomic diffusion has not yet significantly impacted the young stars of this cluster. We thoroughly analyzed the chemical abundances of twelve elements (C, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, and Fe) in 80 F, G, and K dwarf stars from the Pleiades, covering a broad range of effective temperatures, from approximately 4500 to 6800 K. We used high-resolution spectra (R∼22.500) in the near-infrared (λ1.51–1.69 µm) from SDSS IV/APOGEE. In our 1D LTE abundance analysis, we derived an average metallicity for the stars of the Pleiades of [Fe/H] = +0.03 ± 0.04 dex, with elemental ratios of [α/Fe] = +0.01 ± 0.05, [odd-z/Fe] = -0.04 ± 0.08, and [iron peak/Fe] = -0.02 ± 0.08. These results align with literature data and expectations for open clusters in the solar neighborhood. We did not detect atomic diffusion in the Pleiades in a statistically significant manner, corroborating the predictions of theoretical models. Our analysis of individual spectral lines revealed a trend of abundance depletion as effective temperature decreases, particularly in stronger lines. An investigation of the causes of these trends suggests that the modeling of van der Waals broadening in the line lists may be inadequate, particularly for the cooler K dwarfs, which exhibit abundances of up to 0.50 dex lower than solar-type stars for some elements.