| Summary: | 博士 === 國立中央大學 === 天文研究所 === 105 === It is the synoptic survey era for the astronomical optical observation. The evolution of the synoptic survey is from the formaer Palomar Sky Survey (PSS), to more recently SDSS, PTF, and CRTS surveys, etc. The major feature of synoptic surveys is wide field-of-view. Therefore, the systematic study on specific astronomical object is the niche of synoptic survey. Luckily, the National Central University joined two large synoptic survey in 2006 for Pan-STARRS1, and 2009 for PTF. These two projects are international cooperation, and many projects were proposed for the potential scientific studies with these surveys. What we are interested in is the variability of cataclysmic variables (CVs). We expected that the long-term variability of CVs are good to study with the PTF project. Therefore, we started the study of long-term variabilities of CVs.
We adopted Downes' catalog of CVs as a reference catalog for our study. A small but quick responsive data retrival system was established by us. We retrieved the light curves of CVs from this system. There are 344 CVs were matched in the PTF database. After filtering out the light curves with a few obsrvations, there are about 100 CVs were selected for further timing analysis. We adopt the Lomb-Scargle and PDM methods to analysis the light curves. Finally, there are 10 CVs found to possess long-term periodic signals. The lnog-term periodicities are possibly caused by different mechanisms. They are possibly from the precession of the accretion disk, hierarchical triple star system, the magnetic filed strength of the companion changes, and other possible mechanisms. We discussed the sources case by case, and concluded that the majority of the mechanism is possibly from the hierarchical triple system. On the other hand, a few sources with shorter long-term periodicities maybe cause by the precesion of the accretion disk. Basically, we could eliminate other possiblity on our CVs with the current evidence. This study is the pilot study on the long-term variability of the CVs with even larger synoptic surveys. When larger synotpic surveys are online, the method for the study may yield more results and help us to clearify the mechanisms of the long-term variabilitys of CVs.
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