Mercs and Comstar ships found us independently on each other which is too much coincidence to happen two times in the row in a very short time period, which means we arrived relatively soon before that, otherwise our version of Earth would have more visitors in our history which our timeline wouldn't forget. From our perspective, we are sure no one arrived on Earth in like 200 years, which compared to more than 400 years of history of BT jump drive would have happened,. We came in contact with "our" aliens and they have been space-faring for a little longer than us, and they also didn't have any experience with Bt universe proving that we are around BT's timeline for a very short time. That's mostly a logical assumption we don't need any in-universe confirmation for. Sadly, we cannot do much in-universe with this knowledge if an event is unobservable, but the rough timing of it can be guessed.And we have no data on any kind of wave form event or actually interaction beyond suddenly the star change and we get a visitor from outside in the form of the mercs who now enjoy very cushy easy jobs. Or was it just the jumpship arrival?