论文标题
A型星中Ca II K线的行为
Behaviors of Ca II K line in A-type stars
论文作者
论文摘要
对于122 a型星（7000 <te <10000 k）的CA II线的合成频谱拟合分析以较大的旋转速度（10 <vsini <300 km/s）的范围应用于3933.68 A（7000 <te <10000 K），以研究CA丰度的行为（尤其是[Ca/h] 39）的行为，尤其是在II的情况下确定的。 AM现象（通常在慢速旋转器中看到）和（ii）它们是否与较弱的Ca I 6162线得出的Ca丰度（[CA/H] 61）一致。据证实，与同一TE的非AM恒星相比，AM恒星中的CA线强度往往较弱，相关的丰度较低，表明AM恒星的光球中CA的缺乏。然而，发现凉爽的AM恒星（TE <8000 K）的明显部分显示出异常的Ca II 3934线特征（即，由于其弱点异常宽），很难解释。 Regarding the comparison between [Ca/H]39 and [Ca/H]61, while both are roughly consistent for hotter stars (Te > 8000 K), the former tends to be lower (by up to -1 dex or even more) than the latter for cooler A stars (Te < 8000 K) including those "weak broad K line" objects, This fact suggests that some special mechanism reducing the strength of Ca II 3934 line is involved at Te < 8000 K where [CA/H] 39不再可靠。而原子扩散由于较深的辐射信封中的元素隔离而导致CA缺陷的原子扩散可能被视为一个有前途的解释，因为它似乎适合[Ca/h] 61在a型星中的定性趋势，而在A型星中不一定要在经典的ca ii am and中不一定的特点，而这种元素的特点是众所周知的特征，而这种元素的特点是众所周知的特征，而这种元素的特点是众所周知的特征。该共振线特有的未知弱化机制可能独立起作用。
A synthetic spectrum-fitting analysis was applied to the Ca II line at 3933.68 A for 122 A-type stars (7000 <Te < 10000 K) in a wide range of rotational velocity (10 < vsini < 300 km/s), in order to study the behaviors of Ca abundances ([Ca/H]39) determined from this Ca II 3934 line, especially in context of (i) how they are related with the Am phenomenon (often seen in slow rotators) and (ii) whether they are consistent with the Ca abundances ([Ca/H]61) derived from the weaker Ca I 6162 line. It was confirmed that Ca line strengths in Am stars tend to be weaker and associated abundances are lower compared to non-Am stars at the same Te, indicating a deficiency of Ca in the photosphere of Am stars. However, an appreciable fraction of cool Am stars (Te < 8000 K) were found to show anomalous Ca II 3934 line feature (i.e., unusually broad for its weakness) which is hard to explain. Regarding the comparison between [Ca/H]39 and [Ca/H]61, while both are roughly consistent for hotter stars (Te > 8000 K), the former tends to be lower (by up to -1 dex or even more) than the latter for cooler A stars (Te < 8000 K) including those "weak broad K line" objects, This fact suggests that some special mechanism reducing the strength of Ca II 3934 line is involved at Te < 8000 K where [Ca/H]39 would be no more reliable. Whereas atomic diffusion causing the deficit of Ca in the photosphere as a result of element segregation in the deeper radiative envelope may be regarded as a promising explanation because it seems to fit in the qualitative trend of [Ca/H]61 in A-type stars, the well-known feature of considerably weak Ca II K line in classical Am stars should not necessarily be attributed to only this element diffusion scenario, for which some unknown weakening mechanism specific to this resonance line may independently be operative.
