  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 delta
Scuti-type pulsating stars, seven eclipsing binaries, and one peculiar variable
star. Judging from the position of delta 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 delta
Scuti-type short period of about 0.044 day as well as a long period of 0.417
day.
