Abstract We report on time-resolved spectroscopic observations of the SU Ursae Majoris dwarf nova, YZ Cnc for over 11 h on two nights during its 2002 January superoutburst. The spectra on the first day only showed absorption-line profiles, while on the second day the lines showed ``W" profiles with blue and red troughs. The radial velocity curve of the absorption troughs and emission peaks of Hβ has an amplitude of 49±10 km s−1 and a phase offset of −0.07±0.04, which are very similar to those measured in quiescence. However, the γ velocity deviates strongly from the systemic velocity measured in quiescence, by some ±60 km s−1. Large shifts of ~70 km s−1 in the orbital-averaged velocity and ~0.09 in the phase are also found in our observations. All these features can be well explained by a precessing, eccentric disk.
Keywords accretion, accretion disks -binaries: close - novae, cataclysmic variables - stars: dwarf novae - stars: individual (YZ Cancri)
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