Top: Na absorption lines. Bottom: K absorption lines. The photospheric spectrum is based on the PHOENIX model described in the text. The residual spectrum is the spectrum minus the brightest spectrum (2010-01-20, the brightest spectrum was normalized to the same continuum level prior to subtraction, the two 2010-01-18 spectra were averaged prior to subtraction). The fit is shown in red (only for the longer spectrum from 20 Jan. for clarity).