V381 Cephei (HR 8164) is a triple star system in the northern constellation of Cepheus. Its apparent magnitude is slightly variable between 5.5 and 5.7.

V381 Cephei

Location of V381 Cephei (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Cepheus
Right ascension	21h 19m 15.682s[1]
Declination	+58° 37′ 24.550″[1]
Apparent magnitude (V)	5.51 - 5.71[2]
Characteristics
Spectral type	M1epIb + B[3]
U−B color index	0.00[4]
B−V color index	+1.34[4]
Variable type	Lc[2]
Astrometry
Radial velocity (Rv)	−14.10[5] km/s
Proper motion (μ)	RA: −1.435[6] mas/yr Dec.: −5.427[6] mas/yr
Parallax (π)	1.59 ± 0.23 mas[6]
Distance	approx. 2,100 ly (approx. 630 pc)
Absolute magnitude (MV)	−5.2[7]
Details
Aa
Mass	7.2[8] - 16[9] M☉
Radius	276[1] R☉
Luminosity	12,940 - 13,550[1] L☉
Temperature	3,745±170[1] K
Ab
Mass	13[9] M☉
B
Mass	11[9] M☉
Age	49.1[8] Myr
Other designations
V381 Cephei, HR 8164, HIP 105259, BD+58°2249, ADS 14864, 2MASS J21191567+5837246, WDS J21193+5837
A: HD 203338
B: HD 203339
Database references
SIMBAD	data

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.[9]

HD 203338 is itself a spectroscopic binary with components Aa and Ab orbiting every 280 years.[9] It forms a VV Cephei-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.[10]

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.[10]

Component B, HD 203339, is a B3 main sequence star with a mass around 11 M_☉.[9]

References