Near-infrared spectroscopy of M dwarfs. IV. A preliminary survey on the carbon isotopic ratio in M dwarfs*
Near-infrared spectroscopy of M dwarfs. IV. A preliminary survey on the carbon isotopic ratio in M dwarfs*
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M矮星的近红外光谱。
DOI：
10.1093/pasj/psw076
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发表时间：
2016
影响因子：
2.3
通讯作者：
T. Tsuji
中科院分区：
文献类型：
--
作者：
T. Tsuji
根据13 CO（3，1）带的中分辨率近红外光谱，估算了48颗M矮星的碳同位素比值，其中48颗M矮星的碳和氧丰度分别由CO和H_2O谱线测定。我们发现了明确的证据，13 CO功能的存在下，第一次在光谱的M矮星。然而，我们观测到的数据的光谱分辨率不足以直接分析13 CO特征。相反，我们比较观察到的光谱与合成光谱假设12 C/13 C = 10，25，50，100，和200的48个M矮星和估计的最佳可能的12 C/13 C比卡方分析。M矮星的12 C/13 C比值从39到200的下限。31颗M矮星的平均值为12 C/13 C = 87 +-21（p.e.），48颗M矮星的12 C/13 C> 127 +-41（p.e.）。这些结果略大于目前星际物质（ISM）的12 C/13 C比值，该比值是根据在毫米波和光波段观测到的分子谱线确定的。由于演化恒星的质量损失导致ISM中的13 C含量随时间增加，因此反映过去ISM的M矮星中的12 C/13 C比值应该大于现在的ISM。在M矮星中，log 13 C/12 C与log Ac的关系显示出很大的分散性，而没有明显的金属丰度依赖性。这一结果与log 16 O/12 C（= log Ao/Ac）对log Ac的作图结果形成了明显的对比，后者显示出与金属丰度较低时的较大值有相当紧密的相关性。这种对比可能是自然的结果，即16 O和12 C是恒星核合成中的初级产物，而13 C至少部分地是次级产物。
Based on the medium resolution near infrared spectra of 13CO (3,1) band, carbon isotopic ratios are estimated in 48 M dwarfs, for which we had determined the carbon and oxygen abundances from CO and H2O lines, respectively. We find clear evidence for the presence of a 13CO feature for the first time in the spectra of M dwarfs. The spectral resolution of our observed data, however, is not high enough to analyze the 13CO feature directly. Instead, we compare observed spectrum with synthetic spectra assuming 12C/13C = 10, 25, 50, 100, and 200 for each of 48 M dwarfs and estimate the best possible 12C/13C ratio by the chi-square analysis. The resulting 12C/13C ratios in M dwarfs distribute from 39 to a lower limit of 200. The mean value of 31 M dwarfs for which 12C/13C ratios are determined is 12C/13C = 87 +- 21 (p.e.), and that of 48 M dwarfs including those with the lower limit of 200 is 12C/13C > 127 +- 41 (p.e.). These results are somewhat larger than the 12C/13C ratio of the present interstellar matter (ISM) determined from the molecular lines observed in the millimeter and optical wavelength regions. Since the amount of 13C in the ISM has increased with time due to mass-loss from evolved stars, the 12C/13C ratios in M dwarfs, reflecting those of the past ISM, should be larger than those of the present ISM. In M dwarfs, log 13C/12C plotted against log Ac shows a large scatter without clear dependence on the metallicity. This result shows a marked contrast to log 16O/12C (= log Ao/Ac) plotted against log Ac, which shows a rather tight correlation with the larger value at the lower metallicity. Such a contrast can be a natural consequence that 16O and 12C are the primary products in the stellar nuclear synthesis while 13C is the secondary product, at least partly.
冷发光恒星：其红外光谱的混合性质
DOI：
--
发表时间：
2008
期刊：
Astronomy & Astrophysics vol. 489
影响因子：
--
作者：
Takashi Tsuji;Takashi Tsuji;Takashi Tsuji
通讯作者：
Takashi Tsuji