标题： 使用CARMENES确认一颗6.5亿年前的亚海王星HD235088 b（TOI-1430 b）的He I蒸发大气 显示英文标题

标题： Confirmation of an He I evaporating atmosphere around the 650-Myr-old sub-Neptune HD235088 b (TOI-1430 b) with CARMENES

摘要： HD235088 (TOI-1430)是一颗已知的年轻恒星，其周围存在一颗亚海王星大小的行星候选体。 我们通过多波段测光验证了HD235088 b的行星属性，并改进了其行星参数，同时获得了宿主恒星的新年龄估算，将其定位在6亿至8亿年之间。 先前对单一凌星的光谱观测发现，在与行星候选体凌星时间一致的情况下，存在He I的过量吸收现象。 在这里，我们利用CARMENES观测的一次凌星确认了HD235088 b大气中存在He I。此外，我们还检测到氦信号强度可能存在变化的迹象，其吸收深度为$-$0.91$\pm$0.11%，比之前的测量值略深（2$\sigma$）。 此外，我们用球对称的一维流体力学模型模拟了He I信号，发现HD235088 b的高层大气以显著的质量损失率（1.5-5）$\times$10$^{10}$g s$^{-1}$的方式逃逸，在相对低温的外流中，温度$T$=3125$\pm$375 K，处于光压限制逃逸的状态。 HD235088 b（$R_{p}$= 2.045$\pm$0.075 R$_{\oplus}$）是迄今为止发现的最小的拥有固体大气探测的行星——不仅仅是He I的探测，还包括任何其他原子或分子。 这使得它成为进一步分析年轻亚海王星大气演化的基准行星。 显示英文摘要

摘要： HD235088 (TOI-1430) is a young star known to host a sub-Neptune-sized planet candidate. We validated the planetary nature of HD235088 b with multiband photometry, refined its planetary parameters, and obtained a new age estimate of the host star, placing it at 600-800 Myr. Previous spectroscopic observations of a single transit detected an excess absorption of He I coincident in time with the planet candidate transit. Here, we confirm the presence of He I in the atmosphere of HD235088 b with one transit observed with CARMENES. We also detected hints of variability in the strength of the helium signal, with an absorption of $-$0.91$\pm$0.11%, which is slightly deeper (2$\sigma$) than the previous measurement. Furthermore, we simulated the He I signal with a spherically symmetric 1D hydrodynamic model, finding that the upper atmosphere of HD235088 b escapes hydrodynamically with a significant mass loss rate of (1.5-5) $\times$10$^{10}$g s$^{-1}$, in a relatively cold outflow, with $T$=3125$\pm$375 K, in the photon-limited escape regime. HD235088 b ($R_{p}$ = 2.045$\pm$0.075 R$_{\oplus}$) is the smallest planet found to date with a solid atmospheric detection - not just of He I but any other atom or molecule. This positions it a benchmark planet for further analyses of evolving young sub-Neptune atmospheres.