"Aren't they there?"
Translation:Nach bhfuil siad ann?
ann is an adverb meaning "there" (both positional, as in this case, and existential, as in bhí fear ann fadó - "there was a man long ago").
ann also the singular 3rd person singular masculine pronomial form of the preposition i - "in it". This is used in phrases like tá airde an dorais ann - "he/it is as tall as the door" and lá fuar atá ann - "It's a cold day".
In this case, it is the positional "there", which can sometimes be replaced by ansin.