# Long-term Periodicities of Cataclysmic Variables with Synoptic Surveys

## TL;DR

This study analyzes long-term periodicities in 344 galactic cataclysmic variables using combined PTF and CRTS data, revealing rare long-term variability likely caused by disk precession, triple systems, or magnetic changes.

## Contribution

It is the first systematic analysis combining PTF and CRTS data to identify long-term periodicities in a large sample of CVs, exploring their possible mechanisms.

## Key findings

- 10 CVs exhibit long-term periodic variability.
- Long-term periods are linked to disk precession or hierarchical triples.
- Different mechanisms likely dominate for different period ranges.

## Abstract

A systematic study on the long-term periodicities of known Galactic cataclysmic variables (CVs) was conducted. Among 1580 known CVs, 344 sources were matched and extracted from the Palomar Transient Factory (PTF) data repository. The PTF light curves were combined with the Catalina Real-Time Transient Survey (CRTS) light curves and analyzed. Ten targets were found to exhibit long-term periodic variability, which is not frequently observed in the CV systems. These long-term variations are possibly caused by various mechanisms, such as the precession of the accretion disk, hierarchical triple star system, magnetic field change of the companion star, and other possible mechanisms. We discuss the possible mechanisms in this study. If the long-term period is less than several tens of days, the disk precession period scenario is favored. However, the hierarchical triple star system or the variations in magnetic field strengths are most likely the predominant mechanisms for longer periods.