1. The Gaia -ESO Survey: CNO abundances in the open clusters Trumpler 20, NGC 4815, and NGC 6705
- Author
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G. Tautvaišienė, A. Drazdauskas, Š. Mikolaitis, G. Barisevičius, E. Puzeras, E. Stonkut*error*ė, Y. Chorniy, L. Magrini, D. Romano, R. Smiljanic, A. Bragaglia, G. Carraro, E. Friel, T. Morel, E. Pancino, P. Donati, F. Jiménez-Esteban, G. Gilmore, S. Randich, R. D. Jeffries, A. Vallenari, T. Bensby, E. Flaccomio, A. Recio-Blanco, M. T. Costado, V. Hill, P. Jofré, C. Lardo, P. de Laverny, T. Masseron, L. Moribelli, S. G. Sousa, S. Zaggia, Tautvaisiene G., Drazdauskas A., Mikolaitis S., Barisevicius G., Puzeras E., Stonkute E., Chorniy Y., Magrini L., Romano D., Smiljanic R., Bragaglia A., Carraro G., Friel E., Morel T., Pancino E., Donati P., Jimenez-Esteban F., Gilmore G., Randich S., Jeffries R.D., Vallenari A., Bensby T., Flaccomio E., Recio-Blanco A., Costado M.T., Hill V., Jofre P., Lardo C., De Laverny P., Masseron T., Moribelli L., Sousa S.G., and Zaggia S.
- Subjects
[open clusters and associations] ,Stars: abundance ,010504 meteorology & atmospheric sciences ,FOS: Physical sciences ,Context (language use) ,Solar radius ,Astrophysics ,01 natural sciences ,7. Clean energy ,Spectral line ,evolution [Galaxy] ,Open clusters and associations: individual: NGC 4815 ,individual: Trumpler 20 [and associations] ,0103 physical sciences ,Galaxy formation and evolution ,Cluster (physics) ,Astronomy, Astrophysics and Cosmology ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,QB ,0105 earth and related environmental sciences ,Line (formation) ,Physics ,Galaxy: evolution ,open clusters ,Open clusters and associations: individual: Trumpler 20 ,Stars: abundances ,individual: NGC4815 [associations] ,Astronomy and Astrophysics ,Open clusters and associations: individual: NGC 6705 ,Stars: evolution ,Space and Planetary Science ,abundances [stars] ,open clusters and ,NGC6705 [individual] ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,13. Climate action ,evolution [stars] ,Open cluster - Abstract
Aim of this work is to determine C, N, and O abundances in stars of Galactic open clusters of the Gaia-ESO survey and to compare the observed abundances with those predicted by current stellar and Galactic evolution models. In this pilot paper, we investigate the first three intermediate-age open clusters. High-resolution spectra, observed with the FLAMES-UVES spectrograph on the ESO VLT telescope, were analysed using a differential model atmosphere method. Abundances of carbon were derived using the C2 band heads at 5135 and 5635.5 {\AA}. The wavelength interval 6470- 6490 {\AA}, with CN features, was analysed to determine nitrogen abundances. Oxygen abundances were determined from the [O i] line at 6300 {\AA}. The mean values of the elemental abundances in Trumpler 20 as determined from 42 stars are: [Fe/H] = 0.10 +- 0.08 (s.d.), [C/H] = -0.10 +- 0.07, [N/H] = 0.50 +- 0.07, and consequently C/N = 0.98 +- 0.12. We measure from five giants in NGC 4815: [Fe/H] = -0.01 +- 0.04, [C/H] = -0.17 +- 0.08, [N/H] = 0.53 +- 0.07, [O/H] = 0.12 +- 0.09, and C/N = 0.79 +- 0.08. We obtain from 27 giants in NGC 6705: [Fe/H] = 0.0 +- 0.05, [C/H] = -0.08 +- 0.06, [N/H] = 0.61 +- 0.07, [O/H] = 0.13 +- 0.05, and C/N = 0.83 +- 0.19. The C/N ratios of stars in the investigated open clusters were compared with the ratios predicted by stellar evolutionary models. For the corresponding stellar turn-off masses from 1.9 to 3.3 solar masses, the observed C/N ratio values are very close to the predictions of standard first dredge-up models as well as to models of thermohaline extra-mixing. The average [O/H] abundance ratios of NGC 4815 and NGC 6705 are compared with the predictions of two Galactic chemical evolution models. The data are consistent with the evolution at the solar radius within the errors., Comment: 13 pages, 11 figures, accepted for publication in Astronomy & Astrophysics, 2014
- Published
- 2015