Omicron Persei

Omicron Persei (ο Persei, abbreviated Omicron Per, ο Per) is a triple star system in the constellation of Perseus. From parallax measurements taken during the Hipparcos mission it is approximately 1,100 light-years (330 parsecs) from the Sun.

ο Persei

Location of ο Persei (circled red)
Observation data Epoch J2000      Equinox J2000
Constellation	Perseus
A
Right ascension	03h 44m 19.13377s[1]
Declination	32° 17′ 17.6874″[1]
Apparent magnitude (V)	3.83[2]
B
Right ascension	03h 44m 19.17122s[3]
Declination	32° 17′ 18.5103″[3]
Apparent magnitude (V)	6.68[4]
Characteristics
A
Spectral type	B1III / B2V[5]
U−B color index	−0.75[2]
B−V color index	+0.05[2]
Variable type	ellipsoidal[6]
Astrometry
Radial velocity (Rv)	+12.20[7] km/s
Absolute magnitude (MV)	−4.4[5]
A
Proper motion (μ)	RA: +6.091[1] mas/yr Dec.: −9.732[1] mas/yr
Parallax (π)	3.0224 ± 0.3827 mas[1]
Distance	approx. 1,100 ly (approx. 330 pc)
Orbit[5]
Primary	Aa
Companion	Ab
Period (P)	4.4191447 days
Semi-major axis (a)	33 R☉
Eccentricity (e)	0.0
Inclination (i)	39±15°
Semi-amplitude (K1) (primary)	111.8 km/s
Semi-amplitude (K2) (secondary)	155.0 km/s
Details
Aa
Mass	14[8] M☉
Radius	9.6[5] R☉
Surface gravity (log g)	3.4[8] cgs
Temperature	22,700[8] K
Rotational velocity (v sin i)	70±5[5] km/s
Ab
Mass	10[8] M☉
Radius	8.9[5] R☉
Surface gravity (log g)	4.0[8] cgs
Temperature	21,000[8] K
Rotational velocity (v sin i)	65±15[5] km/s
Age	15[5] Myr
Other designations
Atik, 38 Persei, ADS 2726 AB, BD+31°642, CCDM J03443+3217AB, GC 4461, GSC 02359-01258, HIP 17448, HR 1131, HD 23180, SAO 56673, WDS J03443+3217AB
Database references
SIMBAD	data

The system consists of a spectroscopic binary pair designated Omicron Persei A and a third companion Omicron Persei B.^[9] A's two components are themselves designated Omicron Persei Aa (officially named Atik /ˈeɪtɪk/, the traditional name of the system)^[10][11] and Ab.

Etymology

ο Persei in optical light

ο Persei (Latinised to Omicron Persei) is the system's Bayer designation. The designations of the two constituents as Omicron Persei A and B, and those of A's components - Omicron Persei Aa and Ab - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).^[12]

It bore the traditional name Atik (also Ati, Al Atik), Arabic for "the shoulder". Some sources attribute the name Atik to the nearby, brighter star Zeta Persei.^[13][14] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)^[15] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.^[16] It approved the name Atik for the component Omicron Persei A on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.^[11]

In Chinese, 卷舌 (Juǎn Shé), meaning Rolled Tongue, refers to an asterism consisting of Omicron Persei, Nu Persei, Epsilon Persei, Xi Persei, Zeta Persei and 40 Persei.^[17] Consequently, the Chinese name for Omicron Persei itself is 卷舌五 (Juǎn Shé wu), "the Fifth Star of Rolled Tongue".^[18]

Properties

A light curve for Omicron Persei A, plotted from TESS data^[19]

Omicron Persei A is a spectroscopic binary consisting of a spectral type B1 giant and a type B2 dwarf orbiting each other every 4.4 days. The orbit is near-circular although its inclination is not precisely known. The two stars are separated by approximately 33 R_☉, the exact value depending on the inclination. The primary is approximately one magnitude brighter than the secondary at visual wavelengths.^[5] The binary pair forms a rotating ellipsoidal variable star, which varies in brightness from visual magnitude 3.79 to 3.88 during the orbital period.^[20]

Omicron Persei lies just north of the open cluster IC 348, but is not catalogued as a member. Both IC 348 and Omicron Persei belong to the Perseus OB2 association.^[21]

Culture

• In the TV series Futurama, the fictional planet Omicron Persei 8 is home to medicinal plants and reptilian extraterrestrials who often attack Earth.^[22][23]
• The USS Atik, named for Omicron Persei Aa, was a ship of the United States Navy.