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The Z Cam stars IW And and V513 Cas are unusual in having outbursts followingtheir standstills in contrast to the usual Z Cam behavior of quiescencefollowing standstills. In order to gain further understanding of theselittle-studied systems, we obtained spectra correlated with photometry from theAAVSO throughout a 3-4 month interval in 2011. In addition, time-resolvedspectra were obtained in 2012 that provided orbital periods of 3.7 hrs for IWAnd and 5.2 hrs for V513 Cas. The photometry of V513 Cas revealed a regularpattern of standstills and outbursts with little time at quiescence, while IWAnd underwent many excursions from quiescence to outburst to short standstills.The spectra of IW And are similar to normal dwarf novae, with strong Balmeremission at quiescence and absorption at outburst. In contrast, V513 Cas showsa much flatter/redder spectrum near outburst with strong HeII emission andprominent emission cores in the Balmer lines. Part of this continuum differencemay be due to reddening effects. While our attempts to model the outburst andstandstill states of IW And indicate a mass accretion rate near 3E-9 solarmasses per year, we could find no obvious reason why these systems behavedifferently following standstill compared to normal Z Cam stars.

A Study of the Unusual Z Cam Systems IW Andromedae and V513 Cassiopeia