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By comparing the evolution of these lines to mirrors temperature (similarly to what Michele Punturo showed in Thermal lines identification and aliasing) we identify these two lines as the alias of the 111 thermal mode of the NI and WI mirrors, whose theoretical value is 10154 Hz (info from Michele Punturo).
Precisely: 9847 Hz is the alias of a 10154 Hz line and is the 111 mode of the NI mirror, and 9850 Hz is the alias of a 10150 Hz line and is the 111 mode of the WI mirror.

Figures 1 and 2, taken from the LineMonitor web page, show time evolution of the two lines between May 18 and July 20.

Figures 3 and 4 show the matching between the time evolution of these new modes (after a sign change and a proper similarity transformation) and the drum modes of the NI and WI mirrors.

Figure 5 is a summary of identified lines between 9600 and 9900 Hz: all main narrow peaks are identified (refer also to entry 17960).