JHK Magnitudes for L and T Dwarfs and Infrared Photometric Systems
JHK Magnitudes for L and T Dwarfs and Infrared Photometric Systems
复制标题
L 和 T 矮星的 JHK 星等和红外光度系统
DOI：
10.1086/381135
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发表时间：
2003
影响因子：
3.5
通讯作者：
S. Leggett
中科院分区：
文献类型：
--
作者：
D. Stephens;S. Leggett
在过去的几年里，发现了大量的超冷L型和T型矮星。这些天体的有效温度范围从2200 K到700 K，它们的大部分辐射都是近红外辐射，它们的光谱能量分布主要由强分子吸收带控制。这些高度结构化的能量分布导致JHK幅度对所使用的确切滤波器带通极其敏感。在T型矮星的例子中，通常使用的光度系统之间的差异可以在J和J-K时分别达到0.4等和0.5等。L型和T型矮星的近红外星等已经通过各种测光系统公布。目前，这些系统获得的数据无法准确地进行比较或组合，因为基于较热恒星颜色的转换对L和T矮星无效。为了解决这个问题，我们合成了一些常见测光系统的J、H和K星等，并给出了与大气最无关的系统（莫纳克亚天文台滤波器组）的转换方程。如果已知矮星的光谱类型，我们的转换允许数据在系统之间转换为0.01等，这比典型的测量不确定性要好。由于L矮星和T矮星的近红外颜色的简并性和固有散射，仅基于颜色进行转换更加困难;在这种情况下，J星等只能转换为0.05等，H和K只能转换为0.02等。
In the last few years a significant population of ultracool L and T dwarfs has been discovered. With effective temperatures ranging from ∼2200 to 700 K, these objects emit most of their radiation in the near‐IR, and their spectral energy distributions are dominated by strong molecular absorption bands. These highly structured energy distributions lead to JHK magnitudes that are extremely sensitive to the exact filter bandpass used. In the case of the T dwarfs, the differences between commonly used photometric systems can be as large as 0.4 mag at J and 0.5 mag at J−K. Near‐IR magnitudes have been published for L and T dwarfs using a variety of photometric systems. Currently, the data obtained with these systems cannot be accurately compared or combined, as transformations based on the colors of hotter stars are not valid for L and T dwarfs. To address this problem, we have synthesized J, H, and K magnitudes for some of the common photometric systems and present transformation equations with respect to the most atmospheric‐independent system, the Mauna Kea Observatory filter set. If the spectral type of the dwarf is known, our transformations allow data to be converted between systems to 0.01 mag, which is better than the typical measurement uncertainty. Transforming on the basis of color alone is more difficult because of the degeneracy and intrinsic scatter in the near‐IR colors of L and T dwarfs; in this case J magnitudes can only be transformed to ≲0.05 mag and H and K to ≲0.02 mag.