Cataclysmic variables from Sloan Digital Sky Survey -- V (2020-2023) identified using machine learning

Keith Inight, Boris T. Gänsicke, Axel Schwope, Scott F. Anderson, Elmé Breedt, Joel R. Brownstein, Sebastian Demasi, Susanne Friedrich, J. J. Hermes, Knox S. Long, Timothy Mulvany, Gautham A. Pallathadka, Mara Salvato, Simone Scaringi, Matthias R. Schreiber, Guy S. Stringfellow, John R. Thorstensen, Nadia L. Zakamska

Published 2024-06-27Version 1

SDSS-V is carrying out a dedicated survey for white dwarfs, single and in binaries, and we report the analysis of the spectroscopy of 505 cataclysmic variables (CVs) and CV candidates obtained during the first 34 months of observations of SDSS-V. We developed a convolutional neural network (CNN) to aid with the identification of CV candidates among the over 2 million SDSS-V spectra obtained with the BOSS spectrograph. The CNN reduced the number of spectra that required visual inspection to $\simeq2$ per cent of the total. We identified 779 CV spectra among the CNN-selected candidates, plus an additional 37 CV spectra that the CNN misclassified, but that were found serendipitously by human inspection of the data. Analysing the SDSS-V spectroscopy and ancillary data of the 505 CVs in our sample, we report 62 new CVs, spectroscopically confirm 243 and refute 13 published CV candidates, and we report 68 new or improved orbital periods. We discuss the completeness and possible selection biases of the machine learning methodology, as well as the effectiveness of targeting CV candidates within SDSS-V. Finally, we re-assess the space density of CVs, and find $1.3\times 10^{-5}\,\mathrm{pc^{-3}}$.