Fig. 1

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Spectra of U Equ obtained in 1994 (top; extracted from Barnbaum et al. 1996) and in 2022– 2023 (bottom). The spectrum completely changed from being dominated by molecular absorption-emission bands and requiring low excitation temperatures into a circumstellar spectrum of partially ionized atomic gas at a much higher excitation temperature. The bottom spectrum was smoothed to match the resolution of the earlier observations. The Earth symbols mark the positions of the strongest telluric features.
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