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XX Persei (IRC +50052 / HIP 9582 / BD+54 444) is a semiregular variable red supergiant star in the constellation Perseus, near the border with Andromeda.
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Variability
XX Persei is a semiregular variable star of sub-type SRc, indicating a cool supergiant. The General Catalogue of Variable Stars gives the period as 415 days. It also shows a long secondary period which was originally given at 4,100 days. A more recent study shows only slow variations with a period of 3,150 ± 1,000 days. Another study failed to find any long period up to 10,000 days.
Distance
The most likely distance of XX Per is 2,290 parsecs, from assumed membership of the Perseus OB1 association.
Characteristics
XX Per is a red supergiant of spectral type M4Ib with an effective temperature of 3,700 K. It has a large infrared excess, indicating surrounding dust at a temperature of 900 K, but no masers have been detected.
XX Persei has a mass of 16 solar masses, above the limit beyond which stars end their lives as supernovae.
Companion
XX Persei has a companion of magnitude 9.7 20.5" away. The combined spectral type has been given as M4Ib + B7V, while the UV spectrum of the companion has been used to derive a spectral classification of A.