Top: asymmetry of the photospheric Ca I line at 6440.8 Å. We show the CARMENES spectrum in black. The asymmetry can be noted as weak bump at about 6441.2 Å. For comparison we also show a PHOENIX model spectrum with T_eff = 4600 K and log g = 3.5 in red and with T_eff = 4400 K and log g = 2.5 in blue. Bottom: zoom on the Ca I line at 6464.36 Å. The asymmetry there is even more severe and suggests that the stellar spectrum should be fitted with a two temperature model.