Mothership? Stargate? Wormhole?
See the movie at https://www.youtube.com/watch?v=51_Qpt_Jylo&NR=1&feature=fvwp (part 1). See the second mothership? in part 2 below.
Frame before appearance of the "donut"
Next frame, 5 minutes later, there it is:
Then, it's stationary for weeks.
Now, see another object (mothership?) do a 5-day flyby: