9 Andromedae

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9 Andromedae
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension  23h 18m 23.32202s[1]
Declination +41° 46′ 25.2031″[1]
Apparent magnitude (V) 5.98[2]
Spectral type A7 V[3] or A7m[2]
B−V color index 0.215±0.002[2]
Variable type β Per[4]
Radial velocity (Rv)−3.8±2.9[2] km/s
Proper motion (μ) RA: −10.266[1] mas/yr
Dec.: −9.791[1] mas/yr
Parallax (π)7.0976 ± 0.0544[1] mas
Distance460 ± 4 ly
(141 ± 1 pc)
Absolute magnitude (MV)0.43[2]
Period (P)3.2196 d
Eccentricity (e)0.03
Inclination (i)60.2[6]°
Periastron epoch (T)2,436,094.876 JD
Semi-amplitude (K1)
71.6 km/s
9 And A
Mass2.48 M
Radius3.51 R
Luminosity49.2 L
Temperature8,200 K
Rotational velocity (v sin i)81[7] km/s
9 And B
Mass1.32 M
Luminosity17.5 L
Temperature6,330 K
Other designations
9 And, AN And, BD+40° 5043, HD 219815, HIP 115065, HR 8864, SAO 52881[8]
Database references

9 Andromedae, abbreviated 9 And by convention, is a variable binary star system in the northern constellation Andromeda. 9 Andromedae is the Flamsteed designation, while it bears the variable star designation AN Andromedae, or AN And. The maximum apparent visual magnitude of the system is 5.98,[2] which places it near the lower limit of visibility to the human eye. Based upon an annual parallax shift of 7.1 mas,[1] it is located 460 light years from the Earth.

This system was determined to be a single-lined spectroscopic binary in 1916 by American astronomer W. S. Adams, and the initial orbital elements were computed by Canadian astronomer R. K. Young in 1920.[6] The pair orbit each other with a period of 3.2196 days and an eccentricity of 0.03.[5] It is an eclipsing binary, which means the orbital plane is inclined close to the line of sight and, from the perspective of the Earth, the stars pass in front of each other, causing two partial eclipses every orbit. During the transit of the secondary in front of the primary, the visual magnitude drops to 6.16, while the eclipse of the secondary by the primary lowers the net magnitude to 6.09.[9]


  1. ^ a b c d e f Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  2. ^ a b c d e f Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  3. ^ Hill, G.; et al. (1975), "MK Classifications of some Northern Hemisphere Binary Systems", Memoirs of the Royal Astronomical Society, 79: 131, Bibcode:1975MmRAS..79..131H.
  4. ^ Samus', N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085.
  5. ^ a b Pourbaix, D.; et al. (2004), "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits", Astronomy & Astrophysics, 424: 727–732, arXiv:astro-ph/0406573, Bibcode:2009yCat....102020P, doi:10.1051/0004-6361:20041213.
  6. ^ a b c Tremko, Jozef; Bakos, Gustav A. (October 1978), "A Photometric Study of the Am Binary System AN Andromedae", Journal of the Royal Astronomical Society of Canada, 72: 263, Bibcode:1978JRASC..72..263T.
  7. ^ Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393: 897–911, arXiv:1201.2052, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943.
  8. ^ "9 And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved September 14, 2018.
  9. ^ Avvakumova, E. A.; et al. (October 2013), "Eclipsing variables: Catalogue and classification", Astronomische Nachrichten, 334 (8): 860, Bibcode:2013AN....334..860A, doi:10.1002/asna.201311942

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