|dc.description.abstract||Cepheids in open clusters can use its period-luminosity relation to determine distance of the open clusters. According to an initial mass function, we expect member stars in open clusters include both low and high mass stars. Based on stellar evolution, 4~20 solar mass stars will eventually enter the instability strip in their lifetime and become Cepheids. However, only 24 Cepheids were found in open clusters. In comparison there are more than 3000 open clusters in our Galaxy, it is not more than 1%.
In this thesis, receiving the Cepheids of open clusters′ data from WEBDA and 2MASS database to make the locus of the instability strip in the Color-Magnitude Diagram. We use the instability strip, spatial membership probability, proper motion membership probability, photometric membership probability and age to look for the open clusters that have candidate Cepheids in 2MASS database. Then observed 6 open clusters that have 12 candidate Cepheids in B, V, R, I bands by SLT in Lulin Observatory in 6~7 months. Final, we analyzed these candidate Cepheids by Differential Photometry, LS Periodogram and Mean Magnitude-Standard Deviation of Magnitude Diagram, and we determined that 12 candidate Cepheids are not Cepheids.
We used 2 new Cepheids of open clusters to examine the filter condition. It showed the instability strip, spatial membership probability, proper motion membership probability and age that can used, but photometric membership probability is not.||en_US|