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

Abstract

For a detailed analysis of stellar chemical abundances, high-resolution spectra in the optical have mainly been \nused, while the development of near-infrared (NIR) spectrograph has opened new wavelength windows. Red giants \nhave a large number of resolved absorption lines in both the optical and NIR wavelengths, but the characteristics of \nthe lines in different wave passbands are not necessarily the same. We present a selection of Fe I lines in the z′, Y, \nand J bands (0.91–1.33 μm). On the basis of two different lists of lines in this range, the Vienna Atomic Line \nDatabase (VALD) and the catalog published by Melendez & Barbuy in 1999 (MB99), we selected sufficiently \nstrong lines that are not severely blended and compiled lists with 107 Fe I lines in total (97 and 75 lines from \nVALD and MB99, respectively). Combining our lists with high-resolution (λ/Δλ\uf0a0=\uf0a028,000) and high signal-tonoise \n(>500) spectra taken with an NIR spectrograph, WINERED, we present measurements of the iron \nabundances of two prototype red giants: Arcturus and μ\uf0a0Leo. A bootstrap method for determining the \nmicroturbulence and abundance together with their errors is demonstrated. The standard deviations of log\uf0f2 Fe \nvalues from individual Fe I lines are significantly smaller when we use the lines from MB99 instead of those from \nVALD. With the MB99 list, we obtained x = 1.20 \uf0b1 0.11 km s-1 and log\uf0f2 Fe = 7.01 \uf0b1 0.05 dex for Arcturus, \nand x = 1.54 \uf0b1 0.17 km s-1 and log\uf0f2 Fe = 7.73 \uf0b1 0.07 dex for μ\uf0a0Leo. These final values show better agreements \nwith previous values in the literature than the corresponding values we obtained with VALD.