Curious about V$SESSION_LONGOPS output
Most likely not queries but system operations, e.g. gather statistics.
Probably nothing to worry about. 

V$SESSION_LONGOPS


  V$SESSION_LONGOPS displays the status of various operations that run
  for longer than 6 seconds (in absolute time). These operations
  currently include many backup and recovery functions, statistics
  gathering, and query execution, and more operations are added for
  every Oracle release.


Just to verify, check opname and target_desc.