AI 中文总结
本研究利用1850颗Kepler与TESS行星数据，发现累积XUV辐射可统一M型矮星与FGK型恒星周围的海王星沙漠下边界，其均匀性显著优于当前热辐射通量。
AI 中文摘要
近距行星系统的结构存在一个显著特征：海王星大小的行星极为稀少，这一现象被称为海王星沙漠，该沙漠覆盖了轨道周期为几天、半径约2至10倍地球半径（$R_{\rm \bigoplus}$）的区域。恒星的X射线与极紫外（XUV）辐射引发的大气侵蚀可能塑造了该沙漠的下边界，而恒星活动对质量的强依赖性则给不同光谱类型恒星的对比带来了复杂性。本研究检验标准化累积XUV辐射暴露是否能将M型矮星与F、G、K型（FGK型）恒星宿主周围的行星下边界置于同一尺度上。分析使用了1850颗开普勒（Kepler）与凌星系外行星巡天卫星（TESS）发现的行星，其中主拟合样本包含677颗半径满足$2.24 < R_p/R_{\bigoplus} < 7.48$的行星。对于50亿年的典型自转历史，拟合得到的M型与FGK型恒星的偏移量，从当前热辐射通量的-1.06 dex变为累积XUV辐射的-0.37 dex，这对应于点估计值压缩了65.4%，宿主自举法得到的中位数压缩为73.4%。在移除特定宿主、按巡天数据划分、采用单位权重、更换边界定义以及使用9种恒星年龄-自转历史的情况下，这种收敛性均保持稳定。在共同周期的原假设下，2000次模拟实现的中位数压缩为59.1%，其中38.9%的实现收敛性不低于实际数据；绝对偏移量缩减统计量给出p值为0.522。累积XUV辐射相比当前热辐射通量是一种显著更均匀的经验坐标，通过开普勒几何与质量依赖的恒星活动映射共同周期边界可得到相似的均匀性，但当前样本无法约束通用的XUV侵蚀阈值。
英文摘要
The architecture of close-in planetary systems includes a conspicuous scarcity of Neptune-size worlds, known as the Neptunian desert. The deficit spans roughly $2$--$10\,R_{\oplus}$ at orbital periods of a few days. Atmospheric erosion by stellar X-rays and extreme-ultraviolet (XUV) radiation may shape its lower boundary, while the strong mass dependence of stellar activity complicates comparisons across spectral type. We test whether standardized cumulative XUV exposure places the lower boundaries around M-dwarf and F-, G-, and K-type (FGK) hosts on a common scale. The analysis uses 1850 Kepler and TESS planets; the primary fit contains 677 planets with $2.24 < R_p/R_{\oplus} < 7.48$. For a 5 Gyr median-rotation history, the fitted M-minus-FGK offset changes from $-1.06$ dex in present bolometric flux to $-0.37$ dex in cumulative XUV. This corresponds to $65.4\%$ compression in the point estimate and a host-bootstrap median of $73.4\%$. The convergence persists under host deletion, survey separation, unit weighting, alternative boundary definitions, and nine stellar age--rotation histories. A common-period null produces a median compression of $59.1\%$ in 2000 realizations, with $38.9\%$ at least as convergent as the data; an absolute offset-reduction statistic gives $p=0.522$. Cumulative XUV is a substantially more uniform empirical coordinate than present bolometric flux. Comparable uniformity follows from mapping a common period edge through Keplerian geometry and mass-dependent stellar activity, leaving a universal XUV erosion threshold unconstrained by the present sample.
Comments9 pages, 2 figures; submitted to The Astronomical Journal. Code and derived data are available on Zenodo: https://doi.org/10.5281/zenodo.22047390. Comments are welcome
