Mg和TiO在近红外的光谱特征：分光光度指数定义和经验校准
Mg and TiO spectral features at the near-IR: Spectrophotometric index definitions and empirical calibrations
摘要：
使用Cenarro等人（2001 a，b）的近红外光谱恒星库，根据库恒星的有效温度、表面重力和金属丰度分析了Mg I在8807埃和附近TiO波段的行为。新的光谱指数的光谱特征-即镁和sTiO-的定义，其敏感性不同的信噪比，光谱分辨率，通量校准，和天空发射线残差的特点。新的两个指数表现出有趣的性质。特别是，镁I揭示了作为一个很好的指标的镁丰度，而sTiO是一个强大的矮到巨冷光谱类型。经验拟合多项式，再现作为恒星大气参数的函数的新指数的强度进行计算，并与拟合函数预测的FORTRAN例程是可用的。深入研究了几个误差源，非太阳[Mg/Fe]比，以及它们对拟合函数残差的影响。根据这个分析，银河系疏散星团M67的[Mg/Fe]丰度不足约为-0.04。
英文摘要：
Using the near-infrared spectral stellar library of Cenarro et al. (2001a,b), the behaviours of the Mg I line at 8807 angstrom and nearby TiO bands are analyzed in terms of the effective temperature, surface gravity, and metallicity of the library stars. New spectroscopic indices for both spectral features -namely MgI and sTiO- are defined, and their sensitivities to different signal-to-noise ratios, spectral resolutions, flux calibrations, and sky emission line residuals are characterized. The new two indices exhibit interesting properties. In particular, MgI reveals as a good indicator of the Mg abundance, whereas sTiO is a powerful dwarf-to-giant discriminator for cold spectral types. Empirical fitting polynomials that reproduce the strength of the new indices as a function of the stellar atmospheric parameters are computed, and a FORTRAN routine with the fitting functions predictions is made available. A thorough study of several error sources, non-solar [Mg/Fe] ratios, and their influence on the fitting function residuals is also presented. From this analysis, a [Mg/Fe] underabundance of ~ -0.04 is derived for the Galactic open cluster M67.
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