It's a ship. It's alien. Calling it the alien ship is perfectly serviceable.

By transdimensional, I mean alternate universes, divergent timelines. With sufficiently advanced technology, it's entirely possible.

And there are any number of possible explanations for how even those not from the ship might be part of this cross-universal mess. There may be an interdimensional portal near the planet. The alien ship might be creating a subtle reality warping effect. But without evidence I can only speculate.