Brown dwarfs with measured dynamical masses and spectra from direct imaging are benchmarks that anchor substellar atmosphere cooling and evolution models. We present Subaru SCExAO/CHARIS infrared spectroscopy of HIP 93398 B, a brown dwarf companion recently discovered by Y. Li et al. (2023), as part of an informed survey using the Hipparcos–Gaia Catalog of Accelerations. This object was previously classified as a T6 dwarf based on its luminosity, with its independently derived age and dynamical mass in tension with existing models of brown dwarf evolution. Spectral typing via empirical standard spectra, temperatures derived by fitting substellar atmosphere models, and J − H, J − K and colors all suggest that this object has a substantially higher temperature and luminosity, consistent with classification as a late-L dwarf near the L/T transition (T = K) with moderate to thick clouds possibly present in its atmosphere. When compared with the latest generation of evolution models that account for clouds with our revised luminosity and temperature for the object, the tension between the model-independent mass/age and model predictions is resolved.

中文翻译：

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多云 L/T 过渡伴星棕色矮星 HIP 93398 B 的 SCExAO/CHARIS 光谱表征


具有测量的动力学质量和直接成像光谱的褐矮星是锚定亚星际大气冷却和演化模型的基准。我们展示了 HIP 93398 B 的斯巴鲁 SCExAO/CHARIS 红外光谱，HIP 93398 B 是 Y. Li 等人（2023 年）最近发现的褐矮星伴星，作为使用 Hipparcos-Gaia 加速度目录进行知情调查的一部分。这个天体以前根据它的光度被归类为 T6 矮星，其独立得出的年龄和动力学质量与现有的褐矮星演化模型处于紧张状态。通过经验标准光谱的光谱类型，通过拟合亚星际大气模型得出的温度，以及J − H、J − K和颜色都表明，这个天体具有更高的温度和光度，这与在L/T过渡（T = K）附近被归类为晚L矮星一致，其大气中可能存在中度至浓厚的云。与最新一代的演化模型相比，我们修改了天体的光度和温度来解释云，与模型无关的质量/年龄与模型预测之间的紧张关系得到了解决。