will security system drain lexus sc 430 new battery when car sits?

Eventually. If it only take a few days to drain the battery you either have a weak battery or excessive drain from a parasitic battery drain.

If you're talking about a few days or a week than no, it shouldn't kill your battery. But if you're talking about a month or two or longer, especially in frigid temperatures, yes your battery will be dead. Hope that helps! Jim