Broad-band photometric colors and effective temperature calibrations for late-type giants. I. Z = 0.02
Broad-band photometric colors and effective temperature calibrations for late-type giants. I. Z = 0.02
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DOI：
10.1051/0004-6361:20053028
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发表时间：
2005-10
影响因子：
6.5
通讯作者：
A. Kučinskas;P. Hauschildt;H. Ludwig;I. Brott;V. Vansevičius;L. Lindegren;T. Tanabé;F. Allard
中科院分区：
文献类型：
--
作者：
A. Kučinskas;P. Hauschildt;H. Ludwig;I. Brott;V. Vansevičius;L. Lindegren;T. Tanabé;F. Allard
我们研究了金属丰度对晚型巨星宽波段光度色的影响，并在[M/H] = -1.0和-2.0的有效温度（T-eff = 3500- 4800 K）和重力（log g = 0.0-2.5）的宽范围内，将合成色与观测到的晚型巨星的光度性质进行了比较。在有效温度高于3800 K时，金属性对合成光度色的影响很小，但在较低的T-eff，T-时，由于分子形成效率的变化，降低了分子的不透明度，影响变大。为了详细比较晚型巨星在T-eff-color和color-color平面上的合成光度色和观测光度色（在[M/H] = -1.0和-2.0两个金属丰度下进行），我们基于合成光度色导出了一组新的T-eff-log g-color关系，在[M/H] =-0.5，-1.0，-1.5，和-2.0。这些关系是基于T-eff- log g尺度，我们得出的文献数据178晚型巨星在10个银河系球状星团（与金属丰度的个别恒星之间[M/H] = -0.7和-2.5），和合成颜色与PHOENIX，MARCS和ATLAS恒星大气代码。结合[M/H] = 0.0时的T-eff- log g-颜色关系（Kucinskas等人，2005年），新关系集涵盖金属丰度[M/H] = 0.0. -2.0（[M/H] = 0.5），有效温度T-eff = 3500. 4800 K（T-eff = 100 K），重力log g =-0.5. 3.0.在[M/H] = -1.0和-2.0时，新的T-eff- log g-色关系与基于晚型巨星观测性质的已发表的T-eff-色关系符合得很好。所有T-eff颜色平面中的差异通常在类似于100 K的范围内。然而，我们发现，基于合成颜色的尺度预测的有效温度往往略高于基于观测的T-eff- color关系，偏移量高达100 K。这在[M/H] = -1.0和-2.0处都清楚地看到，尤其是在T-eff-（B - V）和T-eff-（V-K）平面中。基于不同恒星大气代码计算的合成颜色的T-eff- log g-色标之间的一致性非常好，典型差异在范围内。在[M/H] =-1.0时，Δ T-eff与70 K相似，在[M/H] =-2.0时，T-eff与40 K相似。（减）
We investigate the effects of metallicity on the broad-band photometric colors of late-type giants, and make a comparison of synthetic colors with observed photometric properties of late-type giants over a wide range of effective temperatures (T-eff = 3500- 4800K) and gravities (log g = 0.0-2.5), at [M/H] = -1.0 and -2.0. The influence of metallicity on the synthetic photometric colors is small at effective temperatures above similar to 3800K, but the effects grow larger at lower T-eff,T- due to the changing effciency of molecule formation which reduces molecular opacities at lower [M/H]. To make a detailed comparison of the synthetic and observed photometric colors of late type giants in the T-eff-color and color-color planes (which is done at two metallicities, [M/H] = -1.0 and -2.0), we derive a set of new T-eff-log g-color relations based on synthetic photometric colors, at [M/H] = -0.5, -1.0, -1.5, and -2.0. These relations are based on the T-eff- log g scales that we derive employing literature data for 178 late-type giants in 10 Galactic globular clusters (with metallicities of the individual stars between [M/H] = -0.7 and -2.5), and synthetic colors produced with the PHOENIX, MARCS and ATLAS stellar atmosphere codes. Combined with the T-eff- log g-color relations at [M/H] = 0.0 (Kucinskas et al. 2005), the set of new relations covers metallicities [M/H] = 0.0... -2.0 ([M/H] = 0.5), effective temperatures T-eff = 3500... 4800 K (T-eff = 100K), and gravities log g = - 0.5... 3.0. The new T-eff- log g-color relations are in good agreement with published T-eff-color relations based on observed properties of late-type giants, both at [M/H] = -1.0 and -2.0. The differences in all T-eff- color planes are typically well within similar to 100K. We find, however, that effective temperatures predicted by the scales based on synthetic colors tend to be slightly higher than those resulting from the T-eff- color relations based on observations, with the offsets up to similar to 100 K. This is clearly seen both at [M/H] = -1.0 and -2.0, especially in the T-eff-(B - V) and T-eff-(V - K) planes. The consistency between T-eff- log g-color scales based on synthetic colors calculated with different stellar atmosphere codes is very good, with typical differences being well within. Delta T-eff similar to 70 K at [M/H] = - 1.0 and. T-eff similar to 40 K at [M/H] = -2.0. (Less)