AI 中文总结
该研究通过对比31个凌行褐矮星的观测与预测半径，发现存在半径相关的膨胀趋势，否定恒星加热为主要原因，该趋势或影响直接成像行星质量估计。
AI 中文摘要
凌行褐矮星为亚恒星演化模型提供了直接的经验检验，目前已知的此类天体已超过50个，我们可在群体层面开展该检验。我们将31个场龄、弱辐照凌行褐矮星的观测质量与半径，与Sonora Diamondback、Sonora Bobcat及ATMO 2020网格模型进行对比，并将其中23个样本与Mukherjee等人（2026）的辐照模型进行对比。在所有对比中，我们均发现了与半径相关的趋势，对$R_{\rm pred}$与$R_{\rm obs}$的拟合得到斜率为0.3-0.4，比1:1关系浅3.7-8σ。根据不同网格模型，平均膨胀率为5%-14%，在最大的天体中可达约20%。我们还测得本征弥散度为8%-12%，是测量不确定度的2至3倍。尽管不同网格模型间的平均膨胀偏移相差3倍，但该弥散度并无此差异，表明它是该群体的属性而非模型的属性。我们未发现其与质量、平衡温度、轨道间距、潮汐加热率或年龄存在关联，仅与宿主恒星金属度存在微弱（1.7σ）趋势。最值得注意的是，未发现其与辐照存在任何趋势，这否定了类似热木星的恒星加热是主要原因的观点。我们反而认为，褐矮星的大气边界条件范围比当前网格模型所表征的更宽。褐矮星的半径膨胀与完全对流的M型矮星相当，且很可能是动力学质量基准中光度差异的凌行对应体。若该趋势延伸至氘燃烧极限以下，将对直接成像行星的质量估计产生偏差，使光度-年龄质量高估数个百分点至10%，并要求光谱重力质量向上修正约20%-45%。
英文摘要
Transiting brown dwarfs provide a direct empirical test of substellar evolutionary models, and with more than 50 now known we can carry out this test at the population level. We compared the observed masses and radii of 31 field-age, weakly irradiated transiting brown dwarfs to the Sonora Diamondback, Sonora Bobcat, and ATMO 2020 grids, and a subset of 23 of them to the irradiated models of Mukherjee et al. (2026). In every comparison we find a radius-dependent trend, with fits of $R_{\rm pred}$ versus $R_{\rm obs}$ yielding slopes of $0.3{-}0.4$, shallower than the one-to-one relation at $3.7{-}8σ$. The mean inflation is $5{-}14\%$ depending on the grid, reaching $\sim20\%$ among the largest objects. We also measure an intrinsic dispersion of $8{-}12\%$, two to three times the measurement uncertainty. While the mean inflation offset varies by a factor of three among grids, this dispersion does not, indicating that it is a property of the population and not the models. We find no correlation with mass, equilibrium temperature, orbital separation, tidal heating rate, or age, and only a marginal ($1.7σ$) trend with host-star metallicity. Most notable is the absence of any trend with irradiation, which argues against hot Jupiter-like stellar heating as the primary cause. We instead suggest that brown dwarfs span a wider range of atmospheric boundary conditions than current grids represent. The brown dwarf radius inflation is comparable to that in fully convective M dwarfs, and it is likely the transiting counterpart to the luminosity discrepancies seen in dynamical-mass benchmarks. If the trend extends below the deuterium-burning limit, it would bias directly imaged planet mass estimates, overestimating luminosity-age masses by several to ten percent and requiring spectroscopic-gravity masses to be revised upward by $\sim20{-}45\%$.
Comments21 pages, 11 figures, 2 tables. Submitted to AAS journals; updated based on referee's comments
