Hm... I'm not the strongest in this area, but I'll try my best. Most of what im seeing is in astronomy though. From the looks of what everyone else is giving me, your best bet might be either Apparent Magnitude or Luminosity. Just, don't quote me in that...
I would suggest finding other sources or asking the question in other sites too if you think that might help. I apologize if they are wrong, again, this isn't exactly my strongest subject.