1998PASP..110.1405T

From Hα radial velocities taken in quiescence we find orbital periods of 0.1591±0.0004 days, or 3.82 hr, for CY Lyr, 0.207584±0.000007 days, or 4.98 hr, for TW Tri, and 0.16870±0.00007 days, or 4.05 hr, for VW Vul. The period of VW Vul is much longer than a previously published value, and the spectrum suggests that we caught this Z Cam star in standstill. The revision of VW Vul's period resolves its problematic status as a short-period dwarf nova that did not show superoutbursts. The quiescent spectra of CY Lyr and TW Tri are typical of dwarf novae between outbursts, and both show the contribution of a late-type secondary, of type ∼M3.5 in CY Lyr and ∼M1 in TW Tri. From the M-dwarf contribution in the quiescent spectrum we estimate distances of ∼330 pc for CY Lyr and ∼800 pc for TW Tri. On 1997 June 30 UT we observed CY Lyr in a rise to outburst, and we present spectra obtained approximately hourly as the object brightened.