Superhumps Behavior during Normal Outbursts in ER Ursae Majoris: Spectroscopy and Photometry

We undertook a 4-day spectroscopic observation and conducted a 13-day photometric study of an SU UMa-type dwarf nova, ER Ursae Majoris. The mean $K$-amplitude for the emission lines is $54 \pm 8 \,\mathrm{km} \,\mathrm{s}^{-1}$and the $\gamma$velocity is $8 \pm 4 \,\mathrm{km} \,\mathrm{s}^{-1}$based on our spectroscopic results. A phase shift of 0.22 was also obtained. Our photometric observation confirms superhumps in normal outbursts of ER UMa, and reconciles contradictory observational results obtained by different authors. We find that superhumps possibly develop near each normal outburst maximum and fade out before the next outburst maximum. If the observed humps were not late superhumps, but ordinary superhumps, much more theoretical work should be done to explain the new phenomena.