On the chemical abundances of Miras in clusters: V1 in the metal-rich globular NGC 5927

Autor: D'Orazi, V., Magurno, D., Bono, G., Matsunaga, N., Braga, V. F., Elgueta, S. S., Fukue, K., Hamano, S., Inno, L., Kobayashi, N., Kondo, S., Monelli, M., Nonino, M., Przybilla, P. N., Sameshima, H., Saviane, I., Taniguchi, D., Thevenin, F., Urbaneja-Perez, M., Watase, A., Arai, A., Bergemann, M., Buonanno, R., Dall'Ora, M., Silva, R., Fabrizio, M., Ferraro, I., Fiorentino, G., Francois, P., Gilmozzi, R., Iannicola, G., Ikeda, Y., Jian, M., Kawakita, H., Kudritzki, R. -P., Lemasle, B., Marengo, M., Marinoni, S., Martinez-Vasquez, C., Minniti, D., Neeley, J., Otsubo, S., Prieto, J. L., Proxauf, B., Romaniello, M., Sanna, N., Sneden, C., Takenaka, K., Tsujimoto, T., Valenti, E., Yasui, C., Yoshikawa, T., Zoccali, M.
Rok vydání: 2018
Předmět:
Druh dokumentu: Working Paper
DOI: 10.3847/2041-8213/aab100
Popis: 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.
Comment: Accepted for publication in the Astrophysical Journal Letters, 9 pages, 3 figures
Databáze: arXiv
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