标题： HIP 99770 b 的轨道和大气通过 VLTI/GRAVITY 的视角 显示英文标题

标题： Orbit and atmosphere of HIP 99770 b through the eyes of VLTI/GRAVITY

摘要： 上下文：从轨道和大气观测中推断巨大系外行星和棕矮星伴星的形成渠道仍然是一个巨大的挑战。需要进一步更精确地直接测量这些伴星的动力学质量，以指导和评估形成、演化和大气模型。我们基于在VLTI/GRAVITY上进行的观测，对HIP 99770 b进行了更新的研究。目标：将新数据与文献中的先前观测相结合，更好地表征HIP 99770 b的轨道、动力学质量以及大气特性，并揭示其可能的形成渠道。方法：我们进行了重新运行的轨道拟合，以进一步限制伴星的动力学质量和轨道解。我们还分析了GRAVITY K波段光谱，将其置于文献数据的背景下，并提取了HIP 99770 b的亮度、年龄、光谱类型、整体性质和大气特征。结果：我们在距离其主星$417\,\mathrm{mas}$的径向距离处检测到了该伴星。新的轨道拟合得出的动力学质量为$17_{-5}^{+6}\,\mathrm{M}_\mathrm{Jup}$，偏心率为$0.31_{-0.12}^{+0.06}$。我们还发现，未来更多的相对天体测量历元不会使动力学质量的约束得到进一步改善，因为来自Hipparcos-Gaia自行异常的相对不确定性占主导地位。Gaia DR4的发布可能会缓解这一困境。我们发现该伴星与光谱类型L8一致，并且其大气中可能存在金属富集。结论：这些结果尚不足以确定伴星的形成渠道。然而，对其整体性质的新约束以及本文提出的额外GRAVITY光谱将有助于未来确定HIP 99770 b的形成历史。 显示英文摘要

摘要： Context: Inferring the likely formation channel of giant exoplanets and brown dwarf companions from orbital and atmospheric observables remains a formidable challenge. Further and more precise directly measured dynamical masses of these companions are required to inform and gauge formation, evolutionary, and atmospheric models. We present an updated study of HIP 99770 b based on observations conducted with VLTI/GRAVITY. Aims: Combining the new data with previous observations from the literature, we characterise HIP 99770 b to better constrain its orbit, dynamical mass, and atmospheric properties, as well as to shed light on its likely formation channel. Methods: We ran a renewed orbit fit to further constrain the dynamical mass of the companion and the orbit solution. We also analysed the GRAVITY K-band spectrum, placing it into context with literature data, and extracting magnitude, age, spectral type, bulk properties and atmospheric characteristics of HIP 99770 b. Results: We detected the companion at a radial separation of $417\,\mathrm{mas}$ from its host. The new orbit fit yields a dynamical mass of $17_{-5}^{+6}\,\mathrm{M}_\mathrm{Jup}$ and an eccentricity of $0.31_{-0.12}^{+0.06}$. We also find that additional relative astrometry epochs in the future will not enable further constraints on the dynamical mass due to the dominating relative uncertainty on the Hipparcos-Gaia proper motion anomaly. The publication of Gaia DR4 will likely ease this predicament. We find that the companion is consistent with spectral type L8 and exhibits a potential metal enrichment in its atmosphere. Conclusions: These results do not yet allow for a definite inference of the companion's formation channel. Nevertheless, the new constraints on its bulk properties and the additional GRAVITY spectrum presented here will aid future efforts to determine the formation history of HIP 99770 b.