Variable Stars in the Open Cluster NGC 2099 (M37)

Time-series CCD photometric observations of the intermediate-age open cluster 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 identified. 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 cluster membership. One new variable, KV 10, shows peculiar light variations with a δ Scuti-type short period of about 0.044 days, as well as a long period of 0.417 days.