标题： 全色特征分析使用JWST/MIRI对Y0棕矮星WISEP J173835.52+273258.9的分析 显示英文标题

标题： Panchromatic characterization of the Y0 brown dwarf WISEP J173835.52+273258.9 using JWST/MIRI

摘要： 冷棕矮星大气是分析温带巨行星的良好训练场所。WISEP J173835.52+273258.9 (WISE 1738) 是一个孤立的 Y0 棕矮星，温度在 350-400 K 之间，处于 T-Y 转换区域。虽然其近红外光谱已被研究，但整体特性与化学成分仍不确定。我们分析了新的 JWST MIRI 中等分辨率光谱（5-18 微米），结合来自 HST/WFC3 和 Gemini/GNIRS 的近红外光谱（0.98-2.2 微米），以更好地约束 WISE 1738 的大气和物理参数。我们使用无云 petitRADTRANS 模型进行神经后验估计（NPE），并利用后验检查、覆盖度和 L-C2ST 诊断方法评估结果。我们的反演确认了之前对 H2O、CH4 和 NH3 的限制，并首次对 CO、CO2 和 15NH3 进行了限制。我们通过 CO 和 CO2 的丰度不满足平衡条件，发现了非平衡化学的证据。估计的特性为温度 402 (+12,-9) K，log g 4.43 (+0.26,-0.34) cm/s2，质量 13 (+11,-7) M_Jup，半径 1.14 (+0.03,-0.03) R_Jup，以及光度 -6.52 (+0.05,-0.04) log L/L_sun。演化模型表明年龄在 1 到 4 Gyr 之间，与 6 小时的自转一致。我们对 15NH3 设定了上限，意味着 14N/15N 比例的 3-sigma 下限为 275。我们还推导出 C/O 比率为 1.35 (+0.39,-0.31)，金属丰度为 0.34 (+0.12,-0.11)，未考虑氧的隔离。 显示英文摘要

摘要： Cold brown dwarf atmospheres are good training grounds for analyzing temperate giant planets. WISEP J173835.52+273258.9 (WISE 1738) is an isolated Y0 brown dwarf with a temperature between 350-400 K, at the T-Y transition. While its near-infrared spectrum has been studied, bulk properties and chemistry remain uncertain. We analyze new JWST MIRI medium-resolution spectra (5-18 micron), combined with near-infrared spectra (0.98-2.2 micron) from HST/WFC3 and Gemini/GNIRS, to better constrain WISE 1738's atmosphere and physical parameters. We use Neural Posterior Estimation (NPE) with a cloud-free petitRADTRANS model and evaluate results using posterior checks, coverage, and L-C2ST diagnostics. Our retrieval confirms previous constraints on H2O, CH4, and NH3, and for the first time constrains CO, CO2, and 15NH3. We find evidence of disequilibrium chemistry through CO and CO2 abundances not expected under equilibrium. Estimated properties are temperature 402 (+12,-9) K, log g 4.43 (+0.26,-0.34) cm/s2, mass 13 (+11,-7) M_Jup, radius 1.14 (+0.03,-0.03) R_Jup, and bolometric luminosity -6.52 (+0.05,-0.04) log L/L_sun. Evolutionary models suggest an age between 1 and 4 Gyr, consistent with a 6-hour rotation. We place an upper bound on 15NH3, implying a 3-sigma lower limit on the 14N/15N ratio of 275. We also derive a C/O ratio of 1.35 (+0.39,-0.31) and metallicity of 0.34 (+0.12,-0.11), without accounting for oxygen sequestration.