40 Persei

This article is about o Persei and is not to be confused with ο (omicron) Persei.

40 Persei is a wide binary star^[13] system in the northern constellation of Perseus. It has the Bayer designation ο Persei, while 40 Persei is the Flamsteed designation. The system is visible to the naked eye as a faint, blue-white hued point of light with an apparent visual magnitude of 4.97.^[2] It is located approximately 1060 light years away from the Sun based on parallax,^[1] and is drifting further away with a radial velocity of +22 km/s.^[6] The system is a member of the Perseus OB2 association of co-moving stars.^[14]

40 Persei

Location of 40 Persei (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Perseus
Right ascension	03h 42m 22.64555s[1]
Declination	+33° 57′ 54.0893″[1]
Apparent magnitude (V)	4.97[2]
Characteristics
Spectral type	B0.5V[3] + A1Vn[4]
U−B color index	−0.84[5]
B−V color index	+0.00[5]
Astrometry
Radial velocity (Rv)	+22.00[6] km/s
Proper motion (μ)	RA: +2.71[1] mas/yr Dec.: −5.91[1] mas/yr
Parallax (π)	3.09±0.21 mas[1]
Distance	1,060 ± 70 ly (320 ± 20 pc)
Absolute magnitude (MV)	−2.26[2]
Details
40 Per A
Mass	12.5[7] M☉
Luminosity	936[2] L☉
Surface gravity (log g)	4.36[8] cgs
Temperature	29,330[9] K
Metallicity [Fe/H]	−0.43[2] dex
Rotational velocity (v sin i)	10[10] km/s
Age	7.2[11] Myr
Other designations
40 Per, BD+33°698, GC 4420, HD 22951, HIP 17313, HR 1123, SAO 56646, CCDM J03424+3358A, WDS J03424+3358A[12]
Database references
SIMBAD	data

The primary component is a massive B-type main-sequence star with a stellar classification of B0.5V.^[3] It is about 7.2^[11] million years old and has a very low projected rotational velocity for an early B-type star,^[15] measured at 10 km/s.^[10] This star has 12.5^[7] times the mass of the Sun and is radiating 936^[2] times the Sun's luminosity from its photosphere at an effective temperature of 29,330 K.^[9] The companion is magnitude 10.04, A-type main-sequence star with a class of A1Vn, and is located at an angular separation of 19.8″ from the primary.^[4]