论文标题
从YJ带中的铁线的线深度估计的红色超级的有效温度，0.97--1.32微米
Effective temperatures of red supergiants estimated from line-depth ratios of iron lines in the YJ bands, 0.97--1.32 micron
论文作者
论文摘要
在许多恒星物理学和银河天文学领域，在观察上确定红色超级巨人（RSG）的有效温度（TEFF）很重要，但是由于模型不确定性主要起源于RSG的扩展大气，仍然存在一些很大的困难。在这里，我们提出了仅使用Fe I线的线深度比（LDR）方法。与传统的LDR方法相比，涉及多个物种的线条，这种LDR对表面重力效应不敏感，并有望规避起源于RSG上层大气的不确定性。因此，我们用红色巨人进行经验校准的LDR- TEFF关系可能直接应用于RSG，尽管需要牢记两组对象之间的各种差异，例如，由三维非LTE效应引起的各种差异。使用潮湿的高分辨率光谱仪观察到的九个众所周知的太阳金属红色巨人的近红外YJ频段光谱，我们选择了12对Fe I线条，最少被其他线条污染。将其LDR-TEFF关系应用于附近的十个RSG，其内部精度为30--70 K的最终teff与以前的观察结果相吻合，假设一维LTE并与日内瓦的恒星演化模型相吻合。 We found no evidence of significant systematic bias caused by various differences, including those in the size of the non-LTE effects, between red giants and RSGs except for one line pair which we rejected because the non-LTE effects may be as large as ~250 K. Nevertheless, it is difficult to evaluate the systematic bias, and further study is required, e.g., with including the three-dimensional non-LTE calculations of all the lines involved.
Determining the effective temperatures (Teff) of red supergiants (RSGs) observationally is important in many fields of stellar physics and galactic astronomy, yet some significant difficulties remain due to model uncertainty originating majorly in the extended atmosphere of RSGs. Here we propose the line-depth ratio (LDR) method in which we use only Fe I lines. As opposed to the conventional LDR method with lines of multiple species involved, the LDR of this kind is insensitive to the surface gravity effects and expected to circumvent the uncertainty originating in the upper atmosphere of RSGs. Therefore, the LDR--Teff relations that we calibrated empirically with red giants may be directly applied to RSGs, though various differences, e.g., caused by the three-dimensional non-LTE effects, between the two groups of objects need to be kept in mind. Using the near-infrared YJ-band spectra of nine well-known solar-metal red giants observed with the WINERED high-resolution spectrograph, we selected 12 pairs of Fe I lines least contaminated with other lines. Applying their LDR--Teff relations to ten nearby RSGs, the resultant Teff with the internal precision of 30--70 K shows good agreement with previous observational results assuming one-dimensional LTE and with Geneva's stellar evolution model. We found no evidence of significant systematic bias caused by various differences, including those in the size of the non-LTE effects, between red giants and RSGs except for one line pair which we rejected because the non-LTE effects may be as large as ~250 K. Nevertheless, it is difficult to evaluate the systematic bias, and further study is required, e.g., with including the three-dimensional non-LTE calculations of all the lines involved.
