Argenteum Astrum was the magical order founded by Aleister Crowley after leaving the Hermetic Order of the Golden Dawn.
It was synonymously known as the Order of the Silver Star, originally developed by S. L. Mathers in the Golden Dawn, but gradually became more adapted toward Crowley’s bisexual orientation. Many known occultists were in its membership including Victor Neuberg, and for a brief period Austin Osman Spare. The Argenteum Astrum (abbreviated A:. A:.) later was incorporated into the Ordo Templi Orientis (O. T. O.). A.G.H
Drury, Nevil. The Watkins Dictionary of Magic. London. Watkins Publishing. 2005. p. 23
Sutin, Lawrence. Do What Thou Wilt: A Life of Aleister Crowley. New York. St. Martin’s Griffin. 2000. p. 208