Gamma Persei

Gamma Persei (Gamma Per, γ Persei, γ Per) is a binary star system in the constellation Perseus. The combined apparent visual magnitude of the pair is +2.9,^[2] making it the fourth-brightest member of the constellation. The distance to this system is of roughly 221 light-years (68 parsecs) with a 1% margin of error.^[6] About 4° to the north of Gamma Persei is the radiance point for the annual Perseid meteor shower.^[11]

Lightcurve of Gamma Persei's 2019 eclipse recorded by NASA's Transiting Exoplanet Survey Satellite (TESS).

γ Persei

Location of γ Persei (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Perseus
Right ascension	03h 04m 47.82011s[1]
Declination	+53° 30′ 23.2626″[1]
Apparent magnitude (V)	2.93[2]
Characteristics
Spectral type	G8III + A2V[3]
U−B color index	+0.45[2]
B−V color index	+0.70[2]
Variable type	EA[4]
Astrometry
Radial velocity (Rv)	+2.5[5] km/s
Proper motion (μ)	RA: −14.194 mas/yr[1] Dec.: −8.684 mas/yr[1]
Parallax (π)	14.735±0.188 mas[6]
Distance	221 ± 3 ly (67.9 ± 0.9 pc)[6]
Absolute magnitude (MV)	–1.50[7] (–1.23/0.01)[8]
Orbit[8]
Period (P)	14.6 yr
Semi-major axis (a)	0.144″
Eccentricity (e)	0.785
Inclination (i)	90.9°
Longitude of the node (Ω)	244.1°
Periastron epoch (T)	1991.08 Besselian
Argument of periastron (ω) (secondary)	170.0°
Details[9]
γ Per A
Mass	3.6±0.2 M☉
Radius	22.7±1.14 R☉
Luminosity	282 L☉
Surface gravity (log g)	2.23±0.08 cgs
Temperature	4,970±70 K
Metallicity [Fe/H]	–0.19[10] dex
Rotation	5,350 days[7]
Rotational velocity (v sin i)	50.0[7] km/s
γ Per B
Mass	2.4±0.2 M☉
Radius	3.9±0.2 R☉
Luminosity	67.6 L☉
Surface gravity (log g)	3.6±0.08 cgs
Temperature	8,400±70 K
Other designations
γ Persei, γ Per, Gamma Per, 23 Persei, BD+52 654, CCDM J03048+5331AP, FK5 108, GC 3664, HD 18925, HIP 14328, HR 915, IDS 02576+5307 AP, PPM 28201, SAO 23789, WDS J03048+5330Aa,Ab.
Database references
SIMBAD	data

This is a wide eclipsing binary system with an orbital period of 5,329.8 days (14.6 years).^[12] This eclipse was first observed in 1990 and lasted for two weeks.^[13] During an eclipse, the primary passes in front of the secondary, causing the magnitude of the system to decrease by 0.55.^[14] The primary component of this system is a giant star with a stellar classification of G9 III.^[15] It has a projected rotational velocity of 50.0 km s⁻¹ and a lengthy estimated rotation period of 14.6 years.^[7] The classification of the secondary remains tentative, with assignments of A3 V^[8] and A2(III).^[15]

Mass estimates for the two stars remain disparate. Using speckle interferometry, McAlister (1982) obtained mass estimates of 4.73 M_☉ for the primary and 2.75 M_☉ for the secondary, where M_☉ is the mass of the Sun. He noted that the mass estimate was too high for the given classification of the primary.^[16] Martin and Mignard (1998) determined masses for both components based on data from the Hipparcos mission: 5.036 ± 0.951 M_☉ for the primary and 2.295 ± 0.453 M_☉ for the secondary. They admit that the high inclination of the orbit resulted in a large margin of error.^[17] Prieto and Lambert (1999) came up with a mass estimate of 3.81 M_☉ for the primary,^[18] while Pizzolato and Maggio (2000) obtained 4.34 M_☉.^[7] Ling et al. (2001) obtained estimates of 2.7 M_☉ for the primary and 1.65 M_☉ for the secondary,^[8] while Kaler (2001) obtained 2.5 and 1.9, respectively.^[13] Diamant et al. (2023) found masses of 3.6 and 2.4 M_☉ for A and B respectively.^[9]

Name and etymology

• This star, together with δ Per, ψ Per, σ Per, α Per and η Per, has been called the Segment of Perseus.^[19]
• In Chinese, 天船 (Tiān Chuán), meaning Celestial Boat, refers to an asterism consisting of γ Persei, η Persei, α Persei, ψ Persei, δ Persei, 48 Persei, μ Persei and HD 27084. Consequently, the Chinese name for γ Persei itself is 天船二 (Tiān Chuán èr, English: the Second Star of Celestial Boat.)^[20]