NN Ser spectrum during total eclipse

This chart represents the spectrum of the cool dwarf star in the variable stellar system NN Ser . The 5 min exposure was obtained during the total phase of the eclipse, when the magnitude of the system was V = 23.0. Several TiO bands are clearly visible in this slightly smoothed tracing. A few deep and narrow "absorption" features are residuals from sky subtraction. The original resolution is 0.55 nm/pix. A spectral type of M6 or later is deduced for NN Ser . The spectrum of a more nearby (and hence much brighter) M6.5 dwarf star (temperature approx. 2600 degrees) is shown below for comparison.