IGRINS RV: A Precision RV Pipeline for IGRINS Using Modified Forward-Modeling in the Near-Infrared and Its Early Science Results

The best way to understand planet formation is to look for planets still forming; however, searching for exoplanets around pre-main sequence stars using the radial velocity (RV) method is challenging because of the strong stellar activity of the host star. As the RV signal produced by the stellar activity (e.g., cold spots) is reduced in the near-infrared (NIR), having both NIR and optical RV measurements can help confirm a planet’s existence. Here we present IGRINS RV, an open-source python package for computing NIR RVs from the Immersion GRating INfrared Spectrometer (IGRINS, currently a guest instrument on Gemini South), a R ~ 45,000 spectrograph with simultaneous coverage of the H band (1.49-1.80 μm) and K band (1.96-2.46 μm). IGRINS RV is unique in its ability to achieve RV precisions of ≲ 30 m/s in both K and H bands without any physical wavelength calibration tools, such as a gas cell or laser frequency comb. Our modified forward modeling technique demonstrates the ability to deliver precision RVs with only telluric templates derived from A0 standard stars observations to provide a source of common-path wavelength calibration. IGRINS RV has successfully recovered planet signals from two main-sequence stars, HD189733 and τBoo A. We will show preliminary results on the optical and the NIR RVs variability analysis for about two dozen T Tauri Stars (TTS, young pre-main sequence stars ≲10 Myr), including 12 classical accreting TTS and 11 weak-line non-accreting TTS. Both show that the amplitudes of their optical RV variations are, in general, larger in general than their NIR RV variations.