well if he were coming from south while i was flying west or east (to make it simple) it would be different. but we both came from the same space station so he was pretty much directly behind me. maybe in an angle of max 10°
Yes, that is important and relevant information. 10°, however, does mean the gap can be shortened somewhat. Once within radar (and distancing) range it is up to the ship being attacked to change vector to the same one as the pirate = no more catching up!