Precision radial velocity (RV) measurements in the near-infrared are a powerful tool to detect and characterize exoplanets around low-mass stars or young stars with higher magnetic activity. However, the presence of strong telluric absorption lines and emission lines in the near infrared that significantly vary in time can prevent extraction of RV information from these spectra by classical techniques, which ignore or mask the telluric lines. We present a methodology and pipeline to derive precision RVs from near-infrared spectra using a forward-modeling technique. We applied this to spectra with a wide wavelength coverage (Y, J, and H bands, simultaneously), taken by the InfraRed Doppler (IRD) spectrograph on the Subaru 8.2-m telescope. Our pipeline extracts the instantaneous instrumental profile of the spectrograph for each spectral segment, based on a reference spectrum of the laser-frequency comb that is injected into the spectrograph simultaneously with the stellar light. These profiles are used to derive the intrinsic stellar template spectrum, which is free from instrumental broadening and telluric features, as well as model and fit individual observed spectra in the RV analysis. Implementing a series of numerical simulations using theoretical spectra that mimic IRD data, we test the pipeline and show that IRD can achieve $ 100$ per pixel at 1000 nm. Dependences of RV precision on various stellar parameters (e.g., $T_{\rm eff}$, $v\sin i$, [Fe/H]) and the impact of telluric-line blendings on the RV accuracy are discussed through the mock spectra analyses. We also apply the RV-analysis pipeline to the observed spectra of GJ 699 and TRAPPIST-1, demonstrating that the spectrograph and the pipeline are capable of an RV accuracy of $<3$ m s$^{-1}$ at least on a time scale of a few months.

中文翻译：

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通过近红外中的前向建模技术精确测量径向速度†

近红外波段的精密径向速度 (RV) 测量是检测和表征低质量恒星或具有较高磁活动的年轻恒星周围的系外行星的强大工具。然而，在近红外区域存在随时间显着变化的强大地吸收线和发射线，可能会阻止通过忽略或掩盖大地线的经典技术从这些光谱中提取 RV 信息。我们提出了一种使用前向建模技术从近红外光谱得出精确 RV 的方法和管道。我们将其应用于由斯巴鲁 8.2 米望远镜上的红外多普勒 (IRD) 光谱仪拍摄的具有宽波长覆盖范围（Y、J 和 H 波段，同时）的光谱。我们的管道为每个光谱段提取光谱仪的瞬时仪器轮廓，基于与恒星光同时注入光谱仪的激光频率梳的参考光谱。这些剖面用于推导出内在恒星模板光谱，该光谱不受仪器展宽和大地特征的影响，以及在 RV 分析中对单个观测光谱进行建模和拟合。使用模拟 IRD 数据的理论光谱实施一系列数值模拟，我们测试了管道并表明 IRD 可以在 1000 nm 处实现每像素 100 美元。通过模拟讨论了 RV 精度对各种恒星参数（例如，$T_{\rm eff}$、$v\sin i$、[Fe/H]）的依赖性以及大地线混合对 RV 精度的影响光谱分析。我们还将 RV 分析管道应用于 GJ 699 和 TRAPPIST-1 的观测光谱，