IGRINS RV: A Python Package for Precision Radial Velocities with Near-Infrared Spectra

Abstract

The relative radial velocity of a star with respect to the Sun can be calculated from its electromagnetic spectrum using the Doppler Effect. This line-of-sight motion, called the Radial Velocity (RV), is an essential tool for astrophysicists. RVs are not only used to detect and characterize exoplanets, but also play a key role in studies of binary stars, star clusters, and moving group member identification. In the past decade, RVs have primarily been measured from spectra in the optical wavelength regime. This is partly because of advancements in detector technology, but also because of the paucity of Earth’s atmospheric absorption features (telluric lines) in the optical. Yet for fainter, cooler, smaller stellar object like M-type stars (stars with mass less than half of the Sun), which emit more energy in the Near-Infrared (NIR), observations in the NIR can save a considerable amount of exposure time. Also, M-type stars are the most common type of star. This along with its size increases the detectability of Earth-like planets around them. Moreover, the stellar activity that can drive false positive exoplanet detections, e.g., star spots carried into view by stellar rotation, is shown to be less severe in the NIR compared to optical.