[论文解读] TIC-65910228 b / NGTS-38 b, a 180 day transiting warm super-Jupiter

Toby Rodel, Solène Ulmer-Moll+64 more|arXiv (Cornell University)|Feb 13, 2026

Stellar, planetary, and galactic studies被引用 0

一句话总结

本文报告发现并表征 TIC-65910228 b / NGTS-38 b，一颗围绕明亮 F 型恒星的180.5 天周期过经的暖型巨行星，具有良好测量的质量与半径。

ABSTRACT

We present the discovery of TIC-65910228 b / NGTS-38 b, a giant exoplanet with a radius of $1.081\pm0.047$ R$_ ext{J}$ and a mass of $4.78_{-0.37}^{+0.40}$ M$_ ext{J}$ on a long-period ($180.52791\pm0.00038$ day), moderately eccentric ($e=0.308\pm0.011$) orbit transiting a bright (V=$10.230\pm0.020$ mag) metal rich ([Fe/H]=$0.33\pm0.09$, 'dex') F6V-F7V type host star. The planet was initially detected from a single transit in TESS Sector 33. A photometric monitoring campaign of 228 nights with NGTS detected a transit egress of the planet, which together with spectroscopic radial velocity monitoring with CORALIE and HARPS identified an orbital period of ~180.5,d. These radial velocity measurements also showed the mass of the companion to be planetary. Additional transit observations coordinated by the TESS follow-up observing program allowed further confirmation and refinement of this period. With its relatively cool equilibrium temperature of $458\pm11$ K, NGTS-38 b joins a small but growing population of well characterised transiting warm-Jupiters and has one of the longest periods of any discovered to date. The target is situated in the LOPS2 field of the upcoming PLATO mission which will allow for greater refinement of the system parameters and potential for the discovery of additional companions too small and/or too long-period to be seen by TESS or NGTS. NGTS-38 b's bright host star and wide orbital separation make it an attractive target for further study, including potential measurement of its spin-orbit alignment or targeted exomoon/ring searches.

研究动机与目标

• 促使研究长周期过经巨行星，以探究形成、迁移与大气保留的机理。
• 为靠近明亮恒星的暖木星提供精确的质量与半径。
• 展示一个协同的光变与分光跟踪工作流程，以确认由太空任务检测到的长周期过经行星。

提出的方法

• 在 TESS Sector 33 使用 STS (Single Transit Search) 管道识别单次过经事件。
• 在 NGTS 光变中检测后逃逸相以限制轨道周期。
• 协调多站 TFOP SG1 跟踪，以捕捉 ingress/egress 并完善星历。
• 用 CORALIE 与 HARPS 获取径向速度测量，以测定质量和恒星参数。
• 进行联合全局建模拟合，将光度与 RV 数据结合，推导轨道解。

Figure 1 : TESS target pixel file for NGTS-38 in sector 33. Each red circle represents a Gaia source down to a magnitude difference of 6 from the target. The circles are also sized according to the difference in magnitude from the target, which is marked with a white x and numbered 1.

实验结果

研究问题

• RQ1 过经伴星的轨道周期、偏心率和物理参数（质量、半径) 是多少？
• RQ2 在已测量的质量与半径下，这个伴星是行星还是棕矮星？
• RQ3 宿星特性为何，以及它们如何影响对行星参数的解释？
• RQ4 长期光变与 RV 数据是否能约束系统中潜在的附加伴星或自旋-轨道对齐？

主要发现

• TIC-65910228 b / NGTS-38 b 的半径为 1.081 ± 0.047 R_J，质量为 4.78 −0.37/+0.40 M_J。
• 轨道周期为 180.52791 ± 0.00038 天，偏心率 e = 0.308 ± 0.011。
• 宿星较亮（V = 10.230 ± 0.020 mag），金属丰度较高（[Fe/H] = 0.33 ± 0.09）。
• 行星的平衡温度为 458 ± 11 K，属于暖木星区间。
• 该系统丰富了长周期过经巨行星的样本，且是未来 RM 测量或系外卫星/环系统搜索的良好靶标。

Figure 2 : Discovery photometry for NGTS-38 b. All TESS lightcurves have been binned to 30 minute cadence for ease of comparison. NGTS data has been binned to nightly cadence and outliers with flux $<0.998$ or flux errors $>0.001$ removed. Red vertical dashes along the bottom x-axis show the expecte