We present 63 new multi-site radial velocity (RV) measurements of the K1III giant HD 76920, which was recently reported to host the most eccentric planet known to orbit an evolved star. We focused our observational efforts on the time around the predicted periastron passage and achieved near-continuous phase coverage of the corresponding RV peak. By combining our RV measurements from four different instruments with previously published ones, we confirm the highly eccentric nature of the system and find an even higher eccentricity of $e=0.8782 \pm 0.0025$ , an orbital period of $415.891^{+0.043}_{-0.039}\,\textrm{d}$ , and a minimum mass of $3.13^{+0.41}_{-0.43}\,\textrm{M}_{\textrm{J}}$ for the planet. The uncertainties in the orbital elements are greatly reduced, especially for the period and eccentricity. We also performed a detailed spectroscopic analysis to derive atmospheric stellar parameters, and thus the fundamental stellar parameters ( $M_*, R_*, L_*$ ), taking into account the parallax from Gaia DR2, and independently determined the stellar mass and radius using asteroseismology. Intriguingly, at periastron, the planet comes to within 2.4 stellar radii of its host star’s surface. However, we find that the planet is not currently experiencing any significant orbital decay and will not be engulfed by the stellar envelope for at least another 50–80 Myr. Finally, while we calculate a relatively high transit probability of 16%, we did not detect a transit in the TESS photometry.

中文翻译：

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HD 76920 b 被锁定：对演化恒星周围最偏心的行星系统的详细分析

我们展示了 K1III 巨星 HD 76920 的 63 项新的多点径向速度 (RV) 测量结果，最近有报道称它拥有已知的围绕一颗演化恒星运行的最古怪的行星。我们将观测工作集中在预测的近星体通道周围的时间上，并实现了相应 RV 峰值的近乎连续的相位覆盖。通过将来自四种不同仪器的 RV 测量结果与之前发表的仪器相结合，我们确认了系统的高度偏心特性，并发现了更高的偏心率 $e=0.8782 \pm 0.0025$ ，轨道周期为 $415.891^{+0.043}_{-0.039}\,\textrm{d}$ , 和最小质量 $3.13^{+0.41}_{-0.43}\,\textrm{M}_{\textrm{J}}$ 为地球。轨道元素的不确定性大大降低，尤其是周期和偏心率。我们还进行了详细的光谱分析以得出大气恒星参数，从而得出基本恒星参数（ $M_*、R_*、L_*$ )，考虑到来自 Gaia DR2 的视差，并使用星震学独立确定了恒星的质量和半径。有趣的是，在近星点处，这颗行星位于其主星表面的 2.4 个恒星半径范围内。然而，我们发现这颗行星目前没有经历任何明显的轨道衰减，并且至少在另外 50-80 Myr 内不会被恒星包层吞噬。最后，虽然我们计算了 16% 的相对较高的凌日概率，但我们没有在 TESS 光度计中检测到凌日。