Variable Stars in the Open Cluster NGC 2099 (M37).pdf

a r X i v : a s t r o - p h / 0 7 0 2 6 7 5 v 1 2 6 F e b 2 0 0 7 Variable Stars in the Open Cluster NGC 2099 (M37) Y. B. Kang Department of Astronomy and Space Science, Chungnam National University, Daejeon 305-764, Korea and Korea Astronomy and Space Science Institute, Daejeon 305-348, Korea ybkang@cnu.ac.kr S.-L. Kim Korea Astronomy and Space Science Institute, Daejeon 305-348, Korea slkim@kasi.re.kr S.-C. Rey Department of Astronomy and Space Science, Chungnam National University, Daejeon 305-764, Korea screy@cnu.ac.kr C.-U. Lee Korea Astronomy and Space Science Institute, Daejeon 305-348, Korea Y. H. Kim Department of Astronomy and Space Science, Chungnam National University, Daejeon 305-764, Korea J.-R. Koo Department of Astronomy and Space Science, Chungnam National University, Daejeon 305-764, Korea and Korea Astronomy and Space Science Institute, Daejeon 305-348, Korea and Y.-B. Jeon Korea Astronomy and Space Science Institute, Daejeon 305-348, Korea ABSTRACT – 2 – Time-series CCD photometric observations of the intermediate-age open clus- ter NGC 2099 were performed to search for variable stars. We also carried out BV photometry to study physical properties of variables in the cluster. Using V -band time-series data, we carefully examined light variations of about 12,000 stars in the range of 10 V 22 mag. A total of 24 variable stars have been identified; seven stars are previously known variables and 17 stars are newly iden- tified. On the basis of observational properties such as light curve shape, period, and amplitude, we classified the new variable stars as nine δ Scuti-type pulsating stars, seven eclipsing binaries, and one peculiar variable star. Judging from the position of δ Scuti-type stars in the color-magnitude diagram, only two stars are likely to have the cluster membership. One new variable KV10 shows peculiar light variations with a δ Scuti-type short period of about 0.044 day as well as a long period of 0.417 day. Subject headings: