Epsilon Andromedae

Epsilon Andromedae, Latinized from ε Andromedae, is a star in the constellation of Andromeda.[4] It can be seen with the naked eye, having an apparent visual magnitude of 4.4.[2] Based upon an annual parallax shift of 21.04 mas as seen from Earth,[1] it is located 155 light years from the Sun. The system is moving closer to the Sun with a radial velocity of −84 km/s.[6] Its orbit in the Milky Way is highly eccentric, causing it to move rapidly relative to the Sun and its neighboring stars.[8]

ε Andromedae

Location of ε Andromedae (lower left of center)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Andromeda
Right ascension 00h 38m 33.34610s[1]
Declination +29° 18′ 42.3135″[1]
Apparent magnitude (V) 4.357[2]
Characteristics
Spectral type G6 III Fe−3 CH1[3]
U−B color index +0.463[2]
B−V color index +0.8713[2]
V−R color index +0.6[4]
R−I color index +0.51[5]
Astrometry
Radial velocity (Rv)−84.43±0.15[6] km/s
Proper motion (μ) RA: −229.04[1] mas/yr
Dec.: −253.11[1] mas/yr
Parallax (π)19.91 ± 0.19 mas[1]
Distance164 ± 2 ly
(50.2 ± 0.5 pc)
Absolute magnitude (MV)+0.69[7]
Details[6]
Mass1.01±0.35 M☉
Radius9.04±0.34 R☉
Luminosity51.3 L☉
Surface gravity (log g)2.88±0.02 cgs
Temperature5,082±20 K
Metallicity [Fe/H]−0.53±0.05 dex
Rotational velocity (v sin i)1.70±0.45 km/s
Age5.71±5.29 Gyr
Other designations
ε And, 30 Andromedae, BD+28° 103, FK5 19, GC 759, HD 3546, HIP 3031, HR 163, SAO 74164, PPM 90002, LTT 10215, NLTT 2065[4]
Database references
SIMBADdata

Properties

This is an evolved G-type giant star with a stellar classification of G6 III Fe−3 CH1.[3] The suffix notation indicates there is a strong underabundance of iron in the spectrum, and an overabundance of cyanogen (CN). ε Andromedae is believed to be a red clump[9] star which is fusing helium in its core. It has about the same mass as the Sun, but has expanded to nine times the Sun's radius. The star is radiating 51 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,082 K.[6]

Naming

In Chinese, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of ε Andromedae, η Andromedae, 65 Piscium, ζ Andromedae, δ Andromedae, π Andromedae, ν Andromedae, μ Andromedae, β Andromedae, σ Piscium, τ Piscium, 91 Piscium, υ Piscium, φ Piscium, χ Piscium and ψ¹ Piscium. Consequently, the Chinese name for ε Andromedae itself is 奎宿四 (Kuí Sù sì, English: the Fourth Star of Legs.)[10]

References
  1. van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  2. Jennens, P. A.; Helfer, H. L. (September 1975). "A new photometric metal abundance and luminosity calibration for field G and K giants". Monthly Notices of the Royal Astronomical Society. 172 (3): 667–679. Bibcode:1975MNRAS.172..667J. doi:10.1093/mnras/172.3.667.
  3. Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
  4. "eps And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved August 28, 2008.
  5. HR 163, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line August 28, 2008.
  6. Jofré, E.; Petrucci, R.; Saffe, C.; Saker, L.; de la Villarmois, E. Artur; Chavero, C.; Gómez, M.; Mauas, P. J. D. (2015). "Stellar parameters and chemical abundances of 223 evolved stars with and without planets". Astronomy & Astrophysics. 574: A50. arXiv:1410.6422. Bibcode:2015A&A...574A..50J. doi:10.1051/0004-6361/201424474. S2CID 53666931.
  7. Takeda, Yoichi; et al. (August 2008). "Stellar Parameters and Elemental Abundances of Late-G Giants". Publications of the Astronomical Society of Japan. 60 (4): 781–802. arXiv:0805.2434. Bibcode:2008PASJ...60..781T. doi:10.1093/pasj/60.4.781. S2CID 16258166.
  8. Epsilon Andromedae Archived 2007-04-28 at the Wayback Machine, Stars, Jim Kaler. Accessed on line August 28, 2008.
  9. Puzeras, E.; et al. (October 2010). "High-resolution spectroscopic study of red clump stars in the Galaxy: iron-group elements". Monthly Notices of the Royal Astronomical Society. 408 (2): 1225–1232. arXiv:1006.3857. Bibcode:2010MNRAS.408.1225P. doi:10.1111/j.1365-2966.2010.17195.x. S2CID 44228180.
  10. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 19 日
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