Fe I Lines in 0.91-1.33 μm Spectra of Red Giants for Measuring the Microturbulence and Metallicities

Kondo, Sohei; Fukue, Kei; Matsunaga, Noriyuki; Ikeda, Yuji; Taniguchi, Daisuke; Kobayashi, Naoto; Sameshima, Hiroaki; Hamano, Satoshi; Arai, Akira; Kawakita, Hideyo; Yasui, Chikako; Izumi, Natsuko; Mizumoto, Misaki; Otsubo, Shogo; Takenaka, Keiichi; Watase, Ayaka; Asano, Akira; Yoshikawa, Tomohiro; Tsujimoto, Takuji
2019, The Astrophysical Journal For a detailed analysis of stellar chemical abundances, high-resolution spectra in the optical have mainly been used, while the development of near-infrared (NIR) spectrograph has opened new wavelength windows. Red giants have a large number of resolved absorption lines in both the optical and NIR wavelengths, but the characteristics of the lines in different wave passbands are not necessarily the same. We present a selection of Fe I lines in the z′, Y, and J bands (0.91-1.33 μm). On the basis of two different lists of lines in this range, the Vienna Atomic Line Database (VALD) and the catalog published by Meléndez & Barbuy in 1999 (MB99), we selected sufficiently strong lines that are not severely blended and compiled lists with 107 Fe I lines in total (97 and 75 lines from VALD and MB99, respectively). Combining our lists with high-resolution (λ/Δλ = 28,000) and high signal-to-noise (>500) spectra taken with an NIR spectrograph, WINERED, we present measurements of the iron abundances of two prototype red giants: Arcturus and μ Leo. A bootstrap method for determining the microturbulence and abundance together with their errors is demonstrated. The standard deviations of {log}{∊}Fe} values from individual Fe I lines are significantly smaller when we use the lines from MB99 instead of those from VALD. With the MB99 list, we obtained ξ =1.20+/- 0.11 {km} {{{s}}}-1 and {log}{∊}Fe}=7.01+/- 0.05 dex for Arcturus, and ξ =1.54+/- 0.17 {km} {{{s}}}-1 and {log}{∊}Fe}=7.73+/- 0.07 dex for μ Leo. These final values show better agreements with previous values in the literature than the corresponding values we obtained with VALD.