| Verf.angabe: | V. D'Orazi, D. Magurno, G. Bono, N. Matsunaga, V.F. Braga, S.S. Elgueta, K. Fukue, S. Hamano, L. Inno, N. Kobayashi, S. Kondo, M. Monelli, M. Nonino, P.N. Przybilla, H. Sameshima, I. Saviane, D. Taniguchi, F. Thevenin, M. Urbaneja-Perez, A. Watase, A. Arai, M. Bergemann, R. Buonanno, M. Dall'Ora, R. Silva, M. Fabrizio, I. Ferraro, G. Fiorentino, P. Francois, R. Gilmozzi, G. Iannicola, Y. Ikeda, M. Jian, H. Kawakita, R.-P. Kudritzki, B. Lemasle, M. Marengo, S. Marinoni, C. Martinez-Vasquez, D. Minniti, J. Neeley, S. Otsubo, J.L. Prieto, B. Proxauf, M. Romaniello, N. Sanna, C. Sneden, K. Takenaka, T. Tsujimoto, E. Valenti, C. Yasui, T. Yoshikawa, and M. Zoccali |
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| Abstract: | We present the first spectroscopic abundance determination of iron, alpha-elements (Si, Ca and Ti) and sodium for the Mira variable V1 in the metal-rich globular cluster NGC 5927. We use high-resolution (R~ 28,000), high signal-to-noise ratio (~200) spectra collected with WINERED, a near-infrared (NIR) spectrograph covering simultaneously the wavelength range 0.91--1.35 micron. The effective temperature and the surface gravity at the pulsation phase of the spectroscopic observation were estimated using both optical (V) and NIR time-series photometric data. We found that the Mira is metal-rich ([Fe/H]=-0.55 \pm 0.15) and moderately alpha-enhanced ([alpha/Fe]=0.15 \pm 0.01, sigma=0.2). These values agree quite well with the mean cluster abundances based on high-resolution optical spectra of several cluster red giants available in the literature ([Fe/H]=-0.47 \pm 0.06, [alpha/Fe]=+0.24 \pm 0.05). We also found a Na abundance of +0.35 \pm 0.20 that is higher than the mean cluster abundance based on optical spectra (+0.18 \pm 0.13). However, the lack of similar spectra for cluster red giants and that of corrections for departures from local-thermodynamical equilibrium prevents us from establishing whether the difference is intrinsic or connected with multiple populations. These findings indicate a strong similarity between optical and NIR metallicity scales in spite of the difference in the experimental equipment, data analysis and in the adopted spectroscopic diagnostics. |
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