RX Andromedae

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RX Andromedae is a variable star in the constellation Andromeda. It is a close-binary system where a white dwarf pulls matter from a companion star through an accretion disk. This process makes the system brighten and fade regularly: it usually shines between magnitudes 10.2 (bright) and 15.1 (faint), with outbursts roughly every 13 days, though the pattern can change.

The binary’s orbital period is about 5.08 hours. The white dwarf is about 0.8 solar masses and very hot (roughly 40,000–45,000 K), while the donor star is cooler (around 3,500 K). RX Andromedae sometimes stays in a low-brightness state for extended periods, similar to VY Sculptoris stars, making it a transitional example between dwarf nova types.

Discovered in 1904–1906 by Arthur Stanley Williams, RX Andromedae has been widely studied in optical and ultraviolet light and has even been detected at radio wavelengths.