Time-resolved CCD photometry is presented of the V \sim 17 optical counterpart of the newly-discovered , hard-X-ray-emitting polar Swift J2619.4+2619 .
A total of \sim 20 hr of data obtained over five nights in various bandpasses ( B,V,R, and I ) reveals a strong quasi-sinusoidal modulation in the light curve at a best-fitting period of 0.1254 d ( 3.01 hr ) , which we associate with the orbital period of the system ( one-day aliases of this period at 0.1114 d and 0.1435 d are considered , but appear to be ruled out by our analysis ) .
The amplitude of the modulation increases with wavelength from \sim 0.8 mag in B to \sim 1.1 mag in R and I .
The increase in amplitude with wavelength is typical of polar systems where the modulated radiation comes from cyclotron emission .
The combination of the relatively long orbital period and the emission of hard X-rays suggest that Swift J2619.4+2619 may be a good candidate for an asynchronous polar system .