论文标题
红色超级二元分数是M31和M33中金属性的函数
The Red Supergiant Binary Fraction as a Function of Metallicity in M31 and M33
论文作者
论文摘要
最近测量了麦哲伦云中进化的红色超级巨人（RSG）二元分数的工作指向15-30％之间的值，大多数同伴是未进化的B型恒星，如恒星进化所决定。在这里，我将此研究扩展到本地组的M31和M33，并研究RSG二元分数随金属性的函数。 M31和M33的最近接近IR光度测量已导致将RSG的完整样本鉴定到限制$ \ log l/l _ {\ odot} \ geq 4.2 $。为了确定这些M31和M33 RSG的二进制部分，我使用了新获得的光谱法组合来识别单个RSG和RSG+OB二进制文件以及档案UV，可见的和近IIR光度法，可见且基于其颜色将RSG分类为单位或biary。然后，我调整了观察到的RSG+OB二元分数以解释观察性偏差。 M33中所得的RSG二进制部分表现出对半乳突距离的强烈依赖性，而内部区域的二进制分数（$ 41.2^{+12.0} _ { - 7.3} $％）比外部区域（$ 15.9^{+12.4} _ { - _ _ { - _ { - 1.9} $％）。在M31中看不到这种趋势。取而代之的是，轻红色区域中的二进制分数在$ 33.5^{+8.6} _ { - 5.0} $％时保持恒定。我得出结论，M33中的RSG二元部分变化是由于金属性依赖性较高，具有较高的RSG二元分数的较高金属性环境。这种依赖性很可能源于由于金属性而导致的RSG物理特性的变化，而是OB二进制的母体分布的变化。
Recent work measuring the binary fraction of evolved red supergiants (RSGs) in the Magellanic Clouds points to a value between 15-30%, with the majority of the companions being un-evolved B-type stars as dictated by stellar evolution. Here I extend this research to the Local Group galaxies M31 and M33, and investigate the RSG binary fraction as a function of metallicity. Recent near-IR photometric surveys of M31 and M33 have lead to the identification of a complete sample of RSGs down to a limiting $\log L/L_{\odot} \geq 4.2$. To determine the binary fraction of these M31 and M33 RSGs, I used a combination of newly obtained spectroscopy to identify single RSGs and RSG+OB binaries as well as archival UV, visible and near-IR photometry to probabilistically classify RSGs as either single or binary based on their colors. I then adjusted the observed RSG+OB binary fraction to account for observational biases. The resulting RSG binary fraction in M33 shows a strong dependence on galactocentric distance with the inner regions having a much higher binary fraction ($41.2^{+12.0}_{-7.3}$%) than the outer regions ($15.9^{+12.4}_{-1.9}$%). Such a trend is not seen in M31; instead, the binary fraction in lightly reddened regions remains constant at $33.5^{+8.6}_{-5.0}$%. I conclude the changing RSG binary fraction in M33 is due to a metallicity dependence with higher metallicity environments having higher RSG binary fractions. This dependence most likely stems not from changes in the physical properties of RSGs due to metallicity, but changes in the parent distribution of OB binaries.
