Gamma Persei
 Location of γ Pegasi (circled) |
|
| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Perseus |
| Right ascension | 03h 04m 47.79074s[1] |
| Declination | +53° 30′ 23.1687″[1] |
| Apparent magnitude (V) | 2.93[2] |
| Characteristics | |
| Spectral type | G9 III + A2–A3[3][4] |
| U−B color index | +0.45[2] |
| B−V color index | +0.70[2] |
| Astrometry | |
| Radial velocity (Rv) | +2.5[5] km/s |
| Proper motion (μ) | RA: +0.51[1] mas/yr Dec.: –5.92[1] mas/yr |
| Parallax (π) | 13.41 ± 0.51[1] mas |
| Distance | 243 ± 9 ly (75 ± 3 pc) |
| Absolute magnitude (MV) | –1.50[6] (–1.23/0.01)[4] |
| Orbit[4] | |
| 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 | |
| γ Per A | |
| Mass | 2.7[4] M☉ |
| Surface gravity (log g) | 2.83[7] cgs |
| Temperature | 5,170[7] K |
| Metallicity [Fe/H] | –0.19[7] dex |
| Rotation | 5,350 days[6] |
| Rotational velocity (v sin i) | 50.0[6] km/s |
| γ Per B | |
| Mass | 1.65[4] M☉ |
| Temperature | 7,895[4] K |
| Other designations | |
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 has been measured using the parallax technique, giving an estimate of roughly 243 light-years (75 parsecs) with a 4% margin of error.[1] About 4° to the north of Gamma Persei is the radiance point for the annual Perseid meteor shower.[8]
This is a wide eclipsing binary system with an orbital period of 5,329.8 days (14.6 years).[9] This eclipse was first observed in 1990 and lasted for two weeks.[10] During an eclipse, the primary passes in front of the secondary, causing the magnitude of the system to decrease by 0.55.[11] The primary component of this system is a giant star with a stellar classification of G9 III.[3] It has a projected rotational velocity of 50.0 km s−1 and a lengthy estimated rotation period of 14.6 years.[6] The classification of the secondary remains tentative, with assignments of A3 V[4] and A2(III).[3]
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.[12] 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.[13] Prieto and Lambert (1999) came up with a mass estimate of 3.81 M☉ for the primary,[14] while Pizzolato and Maggio (2000) obtained 4.34 M☉.[6] Ling et al. (2001) obtained estimates of 2.7 M☉ for the primary and 1.65 M☉ for the secondary,[4] while Kaler (2001) obtained 2.5 and 1.9, respectively.[10]
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.[15]
- 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, γ Persei itself is known as 天船二 (Tiān Chuán èr, English: the Second Star of Celestial Boat.)[16]
References
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- ↑ 2.0 2.1 2.2 2.3 Lua error in package.lua at line 80: module 'strict' not found.
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- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Lua error in package.lua at line 80: module 'strict' not found.
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- ↑ 10.0 10.1 Lua error in package.lua at line 80: module 'strict' not found.
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- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日
