A COMPARISON OF NEAR-INFRARED PHOTOMETRY AND SPECTRA FOR Y DWARFS WITH A NEW GENERATION OF COOL CLOUDY MODELS
A COMPARISON OF NEAR-INFRARED PHOTOMETRY AND SPECTRA FOR Y DWARFS WITH A NEW GENERATION OF COOL CLOUDY MODELS
复制标题
Y矮星近红外光度测量和光谱与新一代冷云模型的比较
DOI：
10.1088/0004-637x/763/2/130
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
C. Visscher
中科院分区：
文献类型：
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作者：
S. Leggett;C. Morley;M. Marley;D. Saumon;J. Fortney;C. Visscher
本文介绍了库欣等人在宽视场红外巡天探测器（WISE）数据中发现的六颗Y矮星的YJHK测光或测光子集。WISEP J041022.71+150248.5、WISEP J173835.52+273258.9和WISEPC J205628.90+145953.3获得YJHK; WISEPC J140518.40+553421.5和WISEP J154151.65225025.2的YJH; WISEP J182831.08+265037.8的YJK。我们还提出了使用GMOS-North获得的WISEPC J205628.90+145953.3的远红外光谱。我们将数据与莫利等人的模型进行了比较，该模型包括硫化物和氯化物冷凝物的云甲板。我们发现，这些以前被忽略的云模型可以很好地再现T9到Y 0矮星的能量分布，除了在5 μm附近模型太亮。这被认为是因为模型没有包括垂直混合引起的化学平衡偏离，这将增加CO和CO2的丰度，降低5 μm处的通量。垂直混合也降低了NH3的丰度，否则NH3将在1.03 μm和1.52 μm处具有在Y 0 WISEPC J205628.90+145953.3中看不到的强吸收特征。我们发现这五个Y 0到Y0.5的矮星有300 Teff K 450，4.0 log g 4.5，和fsed 3。这些温度和重力意味着木星的质量范围为5-15 M，年龄约为5 Gyr。我们认为WISEP J182831.08+265037.8是一个双星系统，因为这更好地解释了它的光度和颜色。我们发现，数据可以与观察到的趋势一致，一般与模型一致，如果该系统是由一个Teff 325 K和log g 4.5小学，和Teff 300 K和log g 4.0中学，对应的质量为10和7 MJupiter和年龄约2 Gyr。如果我们的反卷积是正确的，那么Teff 300 K无云模型在K和W2的通量太微弱了0.5-1.0马格。我们将在我们的下一代模型中解决这一差异，该模型将包含水云和混合。
We present YJHK photometry, or a subset, for the six Y dwarfs discovered in Wide-field Infrared Survey Explorer (WISE) data by Cushing et al. The data were obtained using the Near-Infrared Imager on the Gemini North telescope; YJHK were obtained for WISEP J041022.71+150248.5, WISEP J173835.52+273258.9, and WISEPC J205628.90+145953.3; YJH for WISEPC J140518.40+553421.5 and WISEP J154151.65225025.2; and YJK for WISEP J182831.08+265037.8. We also present a far-red spectrum obtained using GMOS-North for WISEPC J205628.90+145953.3. We compare the data to Morley et al. models, which include cloud decks of sulfide and chloride condensates. We find that the models with these previously neglected clouds can reproduce the energy distributions of T9 to Y0 dwarfs quite well, other than near 5 μm where the models are too bright. This is thought to be because the models do not include departures from chemical equilibrium caused by vertical mixing, which would enhance the abundance of CO and CO2, decreasing the flux at 5 μm. Vertical mixing also decreases the abundance of NH3, which would otherwise have strong absorption features at 1.03 μm and 1.52 μm that are not seen in the Y0 WISEPC J205628.90+145953.3. We find that the five Y0 to Y0.5 dwarfs have 300 ≲ Teff K ≲ 450, 4.0 ≲ log g ≲ 4.5, and fsed ≈ 3. These temperatures and gravities imply a mass range of 5–15 MJupiter and ages around 5 Gyr. We suggest that WISEP J182831.08+265037.8 is a binary system, as this better explains its luminosity and color. We find that the data can be made consistent with observed trends, and generally consistent with the models, if the system is composed of a Teff ≈ 325 K and log g ≲ 4.5 primary, and a Teff ≈ 300 K and log g ≳ 4.0 secondary, corresponding to masses of 10 and 7 MJupiter and an age around 2 Gyr. If our deconvolution is correct, then the Teff ≈ 300 K cloud-free model fluxes at K and W2 are too faint by 0.5–1.0 mag. We will address this discrepancy in our next generation of models, which will incorporate water clouds and mixing.