Wavelength ranges used in this work. For the determination of the stellar parameters through FSF, we use a section of the K-band (2.19 to 2.34 μm, see Sect. 3.1). For the determination of the nominal spectral resolution (Sect. 5), we divide the wavelength range into four sections representing respectively the J (1.04–1.44 μm) and H (1.46–1.80 μm) bands, as well as the atomic (1.90–2.14 μm) and molecular-dominated (2.14–2.41 μm) ranges of the K-band.