Yes, given the time interval and given the log snippet you posted, I'd guess with confidence that it's the heartbeat api. (that's the normal time interval, though I do think it slows down after a period of inactivity) It's not something I've actually tried to do, and I wasn't 100% sure if what I gave you would work.
Is there a reason you need to have multiple admin pages open constantly? The obvious and easiest solution is not to do that.
Maybe Pippin or someone else knows, but I'm not sure how to disable it (or if you really should), but I may look into it when I have more time over the weeekend...