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R Aquarii

A casual observer of R Aquarii over the past several decades might've noticed something slightly out of the ordinary with this Mira variable, as the depth of its minimum seems to undulate slowly over the course of many years.  An observer of the 1920s and 1930s would've seen something much more spectacular though, as shown by this light curve.  R Aqr is both a Mira and a symbiotic (Z Andromedae) variable; the Mira star is in binary orbit with a companion that's accreting matter from the Mira component.  During this time period, the companion became so bright that its light overwhelmed that from the Mira component for most of the Mira pulsation cycle.  By the early 1940s, the companion seemed to settle down, and no similar outbursts have been seen since.  That doesn't mean we won't see one, which is why it's important to keep watching!

AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484