Spectroscopically Identified Cataclysmic Variables from the LAMOST Survey. II. Period Estimates

Abstract

We examine a sample of 340 cataclysmic variables (CVs) from the latest data release of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey, along with 18 objects that are newly classified as CVs. In this paper, we focus on investigating the photometric behaviors of these CVs using data from time-domain surveys. The orbital periods of three new and five previously known objects are determined from the long-term light curves displaying eclipses or ellipsoidal variations, and/or time-resolved spectra from LAMOST. For another 16 CVs with measured periods, it is more reliable to obtain consistent periods using light curves from different surveys, as the periods derived from single-site data are still questionable. Follow-up observations are needed to confirm whether the periods have physical meanings or are orbital-related. In our sample, we find that most of the objects have longer periods above the 2 ∼ 3 hr gap. Besides period estimates, we also carry out a separate detailed analysis of some valuable CVs, in terms of spectral characteristics and subtype determination. Finally, we discuss the observational properties of this sample, including the distributions of orbital periods, absolute magnitudes, and the statistical properties of each subclass of CVs. In addition, we pick out six non-CV systems, including five illumination-effect binaries, as well as one hot subdwarf, that we came across when searching for CVs, and we investigate their properties based on the spectra and photometric data.

Keywords

• Cataclysmic variable stars
• Spectroscopy
• Photometry
• Period determination