Peculiar emission lines in the spectrum of the flare star YZ Canis Minoris

During a series of spectral scans in search of flares on the dMe star YZ CMi the authors observed prominent chromospheric emission lines of Hγ λ4340, Hδ λ4100, Ca II H λ3968 blended with H λ3970, Ca II K λ3934, and Hζ λ3889. During one five-minute scan the authors recorded the following peculiar transient phenomena: (1) the appearance of an exceptionally strong line at ≡λ4007; (2) the simultaneous appearance of another prominent feature at ≡λ4276; and (3) a change in the ratio of (Ca II H+H)/Ca II K. The authors discuss the possible origin of this unusual transient spectrum.