Omicron Andromedae

Omicron Andromedae (ο And, ο Andromedae) is a star system in the constellation Andromeda. It is approximately 692 light years from Earth. The system as a whole is classified as a blue-white B-type giant, with a mean combined apparent magnitude of +3.62.

"1 Andromedae" and "1 And" redirect here. For the galaxy, see Andromeda I. For ι Andromedae, see Iota Andromedae. For other uses, see And 1.
Omicron Andromedae

Location of ο Andromedae (far right)
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension  23h 01m 55.26s[1]
Declination +42° 19′ 33.69″[1]
Apparent magnitude (V) 3.62[2] (3.55 - 3.78[3])
Characteristics
Spectral type B6IIIpe + A2p[4]
U−B color index -0.53[2]
B−V color index -0.09[2]
Variable type γ Cas[5][3]
Astrometry
Radial velocity (Rv)-14.0[6] km/s
Proper motion (μ) RA: +16.846[1] mas/yr
Dec.: -9.108[1] mas/yr
Parallax (π)9.21 ± 0.83[1] mas
Distance350 ± 30 ly
(109 ± 10 pc)
Absolute magnitude (MV)−2.6[7]
Orbit[8][9]
PrimaryA
CompanionB
Period (P)117.4 yr
Semi-major axis (a)0.295″
Eccentricity (e)0.371
Inclination (i)109.6°
Orbit[8][9]
PrimaryAa
CompanionAb
Period (P)5.6 yr
Semi-major axis (a)0.061″
Eccentricity (e)0.22
Inclination (i)152.0°
Orbit[10][9]
PrimaryBa
CompanionBb
Period (P)33.01 days
Eccentricity (e)0.24
Semi-amplitude (K1)
(primary)		54.8±0.8 km/s
Semi-amplitude (K2)
(secondary)		71.6±0.8 km/s
Details
ο And Aa
Mass3.6 + 2.9[4] M☉
Radius6.6[7] R☉
Luminosity1,380[11] L☉
Temperature13,800[11] K
Rotational velocity (v sin i)240[11] km/s
ο And Ab
Mass2.4[4] M☉
ο And B
Mass3.6[4] M☉
Age50.1 ± 6.8[12] Myr
Other designations
FK5 869, 1 And, BD+41°4664, CDS 1436, HIP 113726, HR 8762, SAO 52609[13]
ο And A: HD 217675
ο And B: HD 217676
Database references
SIMBADdata

System

Omicron Andromedae is a multiple star containing at least four components. It is thought to consist of two close pairs in a wider orbit, making a four-star system. This star system has a peculiar velocity of 34.5 ± 5.9 km/s.[12]

The components A and B were first resolved in 1949, when they were reported to be separated by less than 0.1".[14] In 1975 they were separated by 0.375"[10] and by 2014 by only 0.21".[15] An orbit has been derived with a period of 117 years.[8]

In 1975, a companion was discovered by speckle interferometry only 0.05" from component A.[4] Components Aa and Ab orbit every 5.6 years.[8]

A fourth component in the system was suspected and in 1988 it was confirmed. Although a clear 33.01 day period was seen, it was unclear which component the fourth star was in orbit with.[10] Eventually, it was settled that component B was a close spectroscopic binary including the fourth star.[8]

Properties

Omicron Andromedae is a Gamma Cassiopeiae type variable star and the system's brightness varies from magnitude +3.58 to +3.78. The variable component is the brightest and most massive star in the system, Aa.[3]

The spectrum is predominantly that of a B6 giant star, from the brightest component in the system. It is a shell star and the spectrum contains emission lines with variable profiles.[4]

Spectral lines similar to an A2 star are also detectable in the spectrum and these are thought to originate in the B component.[4]

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References
  1. 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. Gaia DR2 record for this source at VizieR.
  2. Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Observatory, Bibcode:1978ppch.book.....N.
  3. 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: B/gcvs. Bibcode:2009yCat....102025S.
  4. 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): 664–679. arXiv:0907.5172. Bibcode:2009AJ....138..664Z. doi:10.1088/0004-6256/138/2/664.
  6. Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Washington: 0, Bibcode:1953GCRV..C......0W.
  7. 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. Zhuchkov, R. Ya; Malogolovets, E. V.; Kiyaeva, O. V.; Orlov, V. V.; Bikmaev, I. F.; Balega, Yu.Yu; Safina, D. I. (2010). "Physical parameters and dynamical properties of the multiple star o and". Astronomy Reports. 54 (12): 1134–1149. doi:10.1134/S1063772910120061.
  9. Tokovinin, Andrei (2018). "The Updated Multiple Star Catalog". The Astrophysical Journal Supplement Series. 235: 6. arXiv:1712.04750. doi:10.3847/1538-4365/aaa1a5.
  10. Hill, G. M.; Walker, G. A. H; Dinshaw, N; Yang, S; Harmance, P (1988). "Omicron Andromedae is quadruple". Publications of the Astronomical Society of the Pacific. 100: 243. Bibcode:1988PASP..100..243H. doi:10.1086/132161.
  11. 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.
  12. 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:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x
  13. "omi And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-06-23.
  14. Wilson, R. H. (1950). "Observations of double stars". The Astronomical Journal. 55: 153. Bibcode:1950AJ.....55..153W. doi:10.1086/106378.
  15. Horch, Elliott P; Van Belle, Gerard T; Davidson, James W; Ciastko, Lindsay A; Everett, Mark E; Bjorkman, Karen S (2015). "Observations of Binary Stars with the Differential Speckle Survey Instrument. VI. Measures during 2014 at the Discovery Channel Telescope". The Astronomical Journal. 150 (5): 151. arXiv:1509.03498. Bibcode:2015AJ....150..151H. doi:10.1088/0004-6256/150/5/151.
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