Mysterious core dump under $ORACLE_HOME/dbs

On a certain system, every once in a while (completely sporadic) I find a large core file (~900M) under $ORACLE_HOME/dbs. Seems like a memory dump to me.

I'm trying to trace it to a process, but am not making much head way. It doesn't leave any clues behind in the bdump,cdump,udumps. I don't see any cronjobs scheduled around the time either.

A "strings -a core" shows me a ton of sql and other stuff. Not sure where to go with it. Ideas anyone?

PS: I thought about using logminer..but then am not sure what I'm looking for even!