R Aquarii is an unusual object in the constellation of Aquarius
Background information and spectra
aka: HD 222800, HIP 117054 and many others
Credit:
ESO / VLT
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R Aquarii (R Aqr) appears as a reddish variable star low down in the sky from southern England, never exceeding a maximum altitude of about 24 degrees.
It is a binary system consisting of a white dwarf and a companion Mira-type red giant variable star, varying roughly from 5m to 13m with a slightly irregular period of about 390 days. The white dwarf siphons off material from the companion’s tenuous outer atmosphere onto its surface via an accretion disc. The buildup of material triggers outbursts from the white dwarf. The result is the system is enclosed in a nebula called Cederblad 211.
The spectrum of the system is dominated by the absorption spectrum of an M type star but has sharp mission lines superimposed.
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