Omicron Andromedae

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"1 Andromedae" and "1 And" redirect here. For the galaxy, see Andromeda I. For the star, see Iota Andromedae. For other uses, see And 1.
Omicron Andromedae
Andromeda stars.png
Location of ο Andromedae (far right)
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension 23h 01m 55.26459s[1]
Declination +42° 19′ 33.5334″[1]
Apparent magnitude (V) 3.62[2] (3.55 - 3.78[3])
Spectral type B6III + A2[4]
U−B color index -0.53[2]
B−V color index -0.09[2]
Variable type γ Cas[5][3]
Radial velocity (Rv) -14.0[6] km/s
Proper motion (μ) RA: +22.99[1] mas/yr
Dec.: +0.88[1] mas/yr
Parallax (π) 4.75 ± 0.53[1] mas
Distance approx. 690 ly
(approx. 210 pc)
Absolute magnitude (MV) −2.6[7]
Primary A
Companion B
Period (P) 159.7 years
Semi-major axis (a) 0.322"
(68.4 AU)
Eccentricity (e) 0.55
Inclination (i) 114.7°
Primary Aa
Companion Ab
Period (P) 8.3 years
Semi-major axis (a) 0.040"
(8.5 AU)
Eccentricity (e) 0.55
Inclination (i) 179.9°
Primary Aa1
Companion Aa2
Period (P) 33.01 days
Eccentricity (e) 0.24
ο And Aa
Mass 3.6 + 2.9[4] M
Radius 6.6[7] R
Luminosity 1,380[8] L
Temperature 13,800[8] K
Rotational velocity (v sin i) 240[8] km/s
ο And Ab
Mass 2.4[4] M
ο And B
Mass 3.6[4] M
Age 50.1 ± 6.8[9] Myr
Other designations
FK5 869, 1 And, BD+41°4664, CDS 1436, HIP 113726, HR 8762, SAO 52609[10]
ο And A: HD 217675
ο And B: HD 217676
Database references

Omicron Andromedae (ο And, ο Andromedae) is a star system in the constellation Andromeda. It is approximately 692 light years from Earth.

Omicron Andromedae is a binary star, whose two components are both spectroscopic binaries themselves, making a four-star system. The system as a whole is classified as a blue-white B-type giant with a mean combined apparent magnitude of +3.62.

The separation of the two brightest components, ο Andromedae A and ο Andromedae B, is 0.34 arcseconds. They have an orbital period of 68.6 years. A is separated from its spectroscopic companion by 0.05 arcseconds. A is a Gamma Cassiopeiae type variable star and the system's brightness varies from magnitude +3.58 to +3.78. This, in turn, has made determination the orbital period of A's spectroscopic binary difficult.[11] B's spectroscopic companion was discovered in 1989, and that binary has a period of 33.01 years.[12]

This star system has a peculiar velocity of 34.5 ± 5.9 km/s.[9]


  1. ^ a b c d e van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752free to read. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  2. ^ a b c Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Observatory, 
  3. ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S. 
  4. ^ a b c d e Olević, D.; Cvetković, Z. (2006). "Dynamical Masses of the Components in o Andromedae". The Astronomical Journal. 131 (3): 1721. Bibcode:2006AJ....131.1721O. doi:10.1086/499539. 
  5. ^ Zasche, P.; Wolf, M.; Hartkopf, W. I.; Svoboda, P.; Uhlař, R.; Liakos, A.; Gazeas, K. (2009). "A Catalog of Visual Double and Multiple Stars with Eclipsing Components". The Astronomical Journal. 138 (2): 664. arXiv:0907.5172free to read. Bibcode:2009AJ....138..664Z. doi:10.1088/0004-6256/138/2/664. 
  6. ^ Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Washington, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W. 
  7. ^ a b Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189 (3): 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601. 
  8. ^ a b c Balona, L. A.; Dziembowski, W. A. (October 1999), "Excitation and visibility of high-degree modes in stars", Monthly Notices of the Royal Astronomical Society, 309 (1): 221–232, Bibcode:1999MNRAS.309..221B, doi:10.1046/j.1365-8711.1999.02821.x. 
  9. ^ a b Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883free to read, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x 
  10. ^ "omi And -- Be Star", SIMBAD Astronomical Object Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-06-23. 
  11. ^ Olević, D.; Cvetković, Z. (March 2006), "Dynamical Masses of the Components in o Andromedae", The Astronomical Journal, 131 (3): 1721–1723, Bibcode:2006AJ....131.1721O, doi:10.1086/499539. 
  12. ^ Hill, G. M.; et al. (February 1988), "Omicron Andromedae is quadruple", Publications of the Astronomical Society of the Pacific, 100: 243–250, Bibcode:1988PASP..100..243H, doi:10.1086/132161. 

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