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RX Andromedae

RX Andromedae is an excellent example of the Z Camelopardalis class of dwarf novae, aka the "Z Cam stars".  These stars are like other dwarf novae in that they undergo outbursts of several magnitudes, lasting for days to a few weeks, caused by their disks rapidly increasing in brightness.  Unlike classical dwarf novae, sometimes they get stuck in an in-between state, where they're much brighter than in quiescence, but not quite in full outburst.  And instead of lasting for a few days or weeks, these standstills can last for months or years.

But RX Andromedae has one important feature not seen in other Z Cam stars -- deep fading events that take the star below its normal quiescent level.  Such events are typical of the VY Sculptoris class of cataclysmic variables, but not the dwarf novae.  RX And showed a major fading event in mid-1996 (around JD 2450300), but resumed its normal alternation between outbursts, quiescence, and standstills within just a few hundred days.  Schreiber, Gansicke and Mattei suggested that RX And is perhaps a transitional, evolving object, and straddles the border between the dwarf nova and the novalike cataclysmic variables.

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