来自一颗成熟迷你海王星的外流氦
Outflowing helium from a mature mini-Neptune
AI总结：
本文宣布探测到来自成熟迷你海王星TOI 2134b的逃逸氦信号，并发现XUV通量与密度比值与观测推断的质量损失率之间存在强相关性。
摘要：
我们宣布探测到来自TOI 2134b的逃逸氦，这是一颗年龄约几Gyr的迷你海王星。平均凌星吸收光谱显示峰值为0.37 ± 0.05%，等值宽度为$W_{\rm avg}=3.3 \pm 0.3$ mÅ。在所有探测到氦的行星中，TOI 2134b是唯一一颗成熟的迷你海王星，具有最小的氦信号，并经历最低的XUV通量。将TOI 2134b置于所有其他氦探测的背景下，我们报告了$F_{\rm XUV}/ρ_{\rm XUV}$（与能量限制的质量损失率成正比）与$R_* W_{\rm avg}$（大致与观测推断的质量损失率成正比）之间强（p=3.0e-5）且理论上预期的相关性。这里，$W_{\rm avg}$是氦吸收的等值宽度，$ρ_{\rm XUV}$是行星在XUV光球层内的密度，但如果使用光学光球层，相关性同样强。TOI 2134b锚定了这一关系，在两个轴上均具有最低值。我们鼓励进一步观测以填补该参数空间的缺失区域并改进$F_{\rm XUV}$的估计。
英文摘要：
We announce the detection of escaping helium from TOI 2134b, a mini-Neptune a few Gyr old. The average in-transit absorption spectrum shows a peak of 0.37 +- 0.05% and an equivalent width of $W_{\rm avg}=3.3 \pm 0.3$ m$Å$. Among all planets with helium detections, TOI 2134b is the only mature mini-Neptune, has the smallest helium signal, and experiences the lowest XUV flux. Putting TOI 2134b in the context of all other helium detections, we report the detection of a strong (p=3.0e-5) and theoretically expected correlation between $F_{\rm XUV}/ρ_{\rm XUV}$ (proportional to the energy-limited mass loss rate) and $R_* W_{\rm avg}$ (roughly proportional to the observationally inferred mass loss rate). Here, $W_{\rm avg}$ is the equivalent width of the helium absorption and $ρ_{\rm XUV}$ is the density of the planet within the XUV photosphere, but the correlation is similarly strong if we use the optical photosphere. TOI 2134b anchors the relation, having the lowest value on both axes. We encourage further observations to fill in missing regions of this parameter space and improve estimates of $F_{\rm XUV}$.
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