Autocorrelation (upper panel) of the frequency spectrum (lower panel) between 10 and 15 d^-1 (with the frequencies outside this region removed) uncovers a multiplet spacing of Δ_f = 0.044 d^-1 that was measured between the peaks near  ~10.4 d^-1 and  ~11.6 d^-1. The peak around  ~0.8 d^-1 originates from the spacing between the structures around 13.2 d^-1 and 14 d^-1 (bottom panel), and those at 10.3 d^-1 and 11 d^-1. The thick grey line is plotted at a separation of 3/T for comparison with the frequency resolution.