Though it may be presumptuous to think that aliens use radio signals. I’d try neutrinos.
I have a follow-up question: Is there more coming?
Maybe whatever catapulted this object toward our sun, flung other objects our way, as well.
Are we looking for more objects coming from the same direction?
And, I hate to bring this up, but wasn’t there a doomsday prediction recently that some planet was going to pop out of nowhere and hit Earth? Quite a coincidence, I’d say.