The Palomar Transient Factory is a project making use of a Schmidt 48 inch telescope located on the Palomar Mountain, which is surveying the sky with dynamical cadences. It was deployed in 2009 and the observed sky region is over 1200 square degrees. We have studied the long-term periodic variabilities of the known galactic cataclysmic variables (CVs). More than 20 of the sources had been found to have long term periodic signals, ranging from several tens of days to several hundreds of days. Some possible scenarios are proposed to explain the results, such as a magnetic field change of the companion star, precession of the accretion disk, triple systems and superoutburst cycles. Some preliminary discussion will be presented in this article.

ABSTRACT
1. PALOMAR TRANSIENT FACTORY
2. CATACLYSMIC VARIABLES WITH PTF/IPTFPROJECT
3. PERIOD ANALYSIS AND CRTS DATA
4. LONG-TERM FOLDED LIGHT CURVES OF CVs
5. POSSIBLE MECHANISMS FOR THE LONG-TERMVARIATIONS
REFERENCES

• Nai-Hui Liao(Graduate Institute of Astronomy, National Central University)
• Po-Sheng Chuang(Graduate Institute of Astronomy, National Central University)
• Ching-Ping Lin(Graduate Institute of Astronomy, National Central University)
• Hung-En Hsieh(Graduate Institute of Astronomy, National Central University)
• Yi-Hao Su(Graduate Institute of Astronomy, National Central University)
• Chin-Ping Hu(Graduate Institute of Astronomy, National Central University)
• Yi Chou(Graduate Institute of Astronomy, National Central University)
• Michael Ting-Chang Yang(Graduate Institute of Astronomy, National Central University)