By David Russell, reporter at OptionMonsterNEW YORK -- Och-Ziff Capital ( OZM) is not a name that often sees unusual option activity, but Thursday its trading lit up OptionMonster's screens. OptionMonster's tracking systems showed early buying in the September 7.50 calls, with about 5,000 purchased in the first 15 minutes of the session for 40 cents. Volume was more than six times the open interest in the strike at the beginning of the day, indicating that these were new positions. Those calls lock in the price investors must pay to buy shares in the hedge-fund operator. They can generate some nice leverage in the event of a rally but will expire worthless if the stock doesn't move before they expire. That leverage was already at play Thursday because Och-Ziff was up about 3% when the options hit. The stock continued marching higher throughout the session and ended up 12% at $7.94. Those calls, meanwhile, inflated 50% to 60 cents. Shares have been falling for a long time and were building support near their lowest level in more than three years. But then the stock rallied after earnings and revenue beat analyst estimates. Overall option volume was 47 times greater than average in the session, with calls outnumbering puts by 8 to 1. Russell has no positions in OZM.