Co-author here. We obtained spectroscopic measurements of 'Oumuamua, and its surface closely matches D-type asteroids and comet nuclei, which are dark, reddish and organic-rich.
Is there a point where you, as a sober professional, start to entertain outlandish theories about something like this? Has this crossed that threshold?
Perhaps someone has discovered warp drives (is gravitational wave detection the first step) and the Federation have sent a ship to observe us.
Anyways, given all the EM radiation we're tossing out into the void, some species' probe out there is going to pick up our existence sooner or later.
And at ~395 earth-moon distances it's difficult to imagine how effective a 400-meter object, disguised as an asteroid, would be at seeing much detail on earth.
But it is tantalizing and fun to imagine--the appearance of a gravity boost... Flat surfaces... Near to earth... Lack of any ice or outgasing, a solid object, many characteristics not seen in other known-asteroids, rotating on its long axis... :)
Ah, but it's a carrier for the small, stealthy probes!
That's what they want you to think!
So you're saying it's a bio-ship! ldenneau confirms it's aliens!