Color-magnitude diagram of GD-1 member stars. The left panel shows stars identified in this work, with gray points representing stars that deviate significantly from the isochrone. The right panel shows GD-1 member stars from Willett et al. (2009), Li et al. (2018), and Huang et al. (2019). Magnitudes were obtained by cross-matching with Gaia Dr3. The isochrone corresponds to an age of 10 Gyr, a distance of 10 kpc, and a metallicity of −2.1 dex.