Characterization of Dwarf Novae Using SDSS Colors

Abstract

Abstract We have developed a method for estimating the orbital periods of dwarf novae from the Sloan Digital Sky Survey (SDSS) colors in quiescence using an artificial neural network. For typical objects below the period gap with sufficient photometric accuracy, we were able to estimate the orbital periods with accuracy to a 1 $\sigma$ error of 22%. The error of the estimation is worse for systems with longer orbital periods. We have also developed a neural-network-based method for categorical classification. This method has proven to be efficient in classifying objects into three categories (WZ Sge type, SU UMa type, and SS Cyg/Z Cam type), and works for very faint objects to a limit of g$=$ 21 mag. Using this method, we have investigated the distribution of the orbital periods of dwarf novae from a modern transient survey (Catalina Real-Time Survey). Using a Bayesian analysis developed by Uemura et al. (2010, PASJ, 62, 613), we have found that the present sample tends to give a flatter distribution to the shortest period and a shorter estimate of the period minimum, which may have resulted from uncertainties in the neural-network analysis and photometric errors. We also provide estimated orbital periods, estimated classifications, and supplemental information on known dwarf novae with the quiescent SDSS photometry.