V381 Cephei (HR 8164) is a

triple star A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. It may sometimes be used to refer to a single star. A large group of stars bound by gravitation is generally called a ''sta ...

system in the northern

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Cepheus Cepheus (Ancient Greek: Κηφεύς ''Kepheús'') may refer to: In Greek mythology * Cepheus (father of Andromeda), and King of Aethiopia * Cepheus (son of Aleus), a king of Tegea, Arcadia In astronomy * Cepheus (constellation), one of the 88 m ...

. Its apparent magnitude is slightly variable between 5.5 and 5.7. It is faintly visible to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnification, magnifying, Optical telescope#Light-gathering power, light-collecting optical instrument, such as a telescope or microsc ...

under good observing conditions. The star was discovered to be a

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...

in 1991, by Elaine M. Halbedel. It was given its

variable star designation In astronomy, a variable-star designation is a unique identifier given to variable stars. It extends the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constellation in whic ...

, V381 Cephei, in 1995.

System

V381 Cephei is a visual double star with components A and B separated by 4.6". The primary is HD 203338 and the secondary is the magnitude 9.2 HD 203339. HD 203338 is itself a spectroscopic binary with components Aa and Ab orbiting every 280 years. It forms a

VV Cephei VV Cephei, also known as HD 208816, is an eclipsing binary star system located in the constellation Cepheus. It is both a B star and shell star. As a 5th magnitude star, it is visible to the naked eye under good observing condition ...

-type binary system with a hot companion which is accreting mass from the primary. The long period means that it exhibits fewer peculiarities than other VV Cephei binaries.

Properties

Component Aa is a red supergiant and its close companion is a B2 main sequence star. The supergiant is a pulsating variable with a small amplitude and poorly defined period. It is generally given spectral class qualifiers indicating peculiarities and emission, which may be associated with the disc around the hot secondary. Component B, HD 203339, is a B3 main sequence star with a mass around .

References

{{DEFAULTSORT:V381 Cephei Cepheus (constellation) Cephei, V381 203338 9 8164 M-type supergiants 105259 B-type main-sequence stars BD+58 2249 J21191567+5837246 Slow irregular variables Emission-line stars Triple star systems