The Aturian is a refinery ship which escaped the Fall of the Twelve Colonies with the Fleet. Refinery ships process raw minerals and metals gathered by a Mining Ship. Unlike a Mining Ship, a Refinery Ship has large processing and storage facilities, and presumably can serve as a fueling vessel.
The Refinery Ship refused to refine more tylium in protest of President Laura Roslin's imprisonment and Col. Tigh's subsequent declaration of martial law ("Resistance").
The fleet has at least one Refinery Ship to process the immense reserves of tyllium mined from an asteroid liberated from a Cylon base in the episode "The Hand of God". It was named in the episode "Resistance".