# # Program information file # PROGRAM_ID 2021B039 PROGRAM_TITLE Magnetic field measurements of M dwarf stars using iSHELL spectra PROGRAM_INV1 Eunkyu Han PROGRAM_INV2 Gregory Mace PROGRAM_INV3 Amber Medina PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT stellar PROGRAM_ABSTRACT_BEG Magnetic fields are ubiquitous in stars and play an important role in stellar evolution. In particular, M dwarfs are known to be magnetically active. The strength of surface magnetic fields is a critical component of atmospheric and interior models of M dwarfs and of determining the habitability of exoplanets orbiting around M dwarfs. However, the formation mechanism of magnetic fields within the M dwarfs is not well-known. Nonetheless, empirical determinations of the magnetic strength of M dwarfs are pivotal in testing the theoretical models of stellar interiors. One way to directly measure the magnetic field strengths is to measure the Zeeman splitting in the magnetically sensitive spectral lines. High-resolution near-infrared spectroscopy offers a great venue for this measurement because the Zeeman splitting gets more prominent at longer wavelengths. We are currently in the process of determining the magnetic field strengths of M dwarfs through the Zeeman splitting measurements using IGRINS spectra. In this proposal, we request to use iSHELL and its high-resolution mode [R=70,000] to observe a selected subset of our M dwarf sample and validate the robustness of our measurements. All stars in our sample have reported magnetic field strengths from various groups using different sets of data and pipelines which are subject to different systematic offsets in the measurements. We will compare and test the measurements with iSHELL data against the IGRINS data for any systematic bias and investigate its impact on the empirical measurements. iSHELL observations will serve as critical components in characterizing the IGRINS detection limit as well as in the validation of magnetic field measurements of hundreds of IGRINS-observed M dwarfs. PROGRAM_ABSTRACT_END