Omicron Andromedae
Location of ο Andromedae (far right)
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension 23h 01m 55.265s[1]
Declination +42° 19′ 33.53″[1]
Apparent magnitude (V) 3.62[2] (3.55 - 3.78[3])
Characteristics
Spectral type B6III[4] (B6IIIpe + A2p)[5]
U−B color index −0.53[2]
B−V color index −0.09[2]
Variable type γ Cas[6][3]
Astrometry
Radial velocity (Rv)-14.0[7] km/s
Proper motion (μ) RA: +22.99[1] mas/yr
Dec.: +0.88[1] mas/yr
Parallax (π)4.75 ± 0.53 mas[1]
Distanceapprox. 690 ly
(approx. 210 pc)
Absolute magnitude (MV)−2.6[8]
Orbit[9]
PrimaryA
CompanionB
Period (P)118.0 yr
Semi-major axis (a)0.304″
Eccentricity (e)0.340
Inclination (i)107.4°
Orbit[10][11]
PrimaryAa
CompanionAb
Period (P)5.6 yr
Semi-major axis (a)0.061″
Eccentricity (e)0.22
Inclination (i)152.0°
Orbit[12][11]
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
Mass9.85[11] M☉
Radius6.6[8] R☉
Luminosity1,380[13] L☉
Temperature13,800[13] K
Rotational velocity (v sin i)240[13] km/s
ο And Ab
Mass4.51[11] M☉
ο And Ba
Mass3.74[11] M☉
ο And Bb
Mass2.86[11] M☉
Age50.1 ± 6.8[14] Myr
Other designations
FK5 869, 1 And, BD+41°4664, CDS 1436, HIP 113726, HR 8762, SAO 52609, PPM 63726[15]
ο And A: HD 217675
ο And B: HD 217676
Database references
SIMBADdata

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.

System

Omicron Andromedae is a multiple star containing at least three components. It may consist of two close pairs in a wider orbit, making a four-star system,[14] although the binarity of the primary star is in doubt.[11] This star system has a peculiar velocity of 34.5 ± 5.9 km/s.[14]

The components A and B were first resolved in 1949, when they were reported to be separated by less than 0.1".[16] In 1975 they were separated by 0.375"[12] and by 2014 by only 0.21".[17] An orbit has been derived with a period of 118 years.[9] The companion is 2.3 magnitudes fainter than the primary star.[5]

In 1975, a companion was discovered by speckle interferometry only 0.05" from component A.[5] Components Aa and Ab orbit every 5.6 years,[10] although the existence of this companion is now doubted.[11]

A spectroscopic binary 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 was the pair seen in the spectrum.[12] Eventually, it was settled that component B was a close spectroscopic binary.[10]

Properties

A light curve for Omicron Andromedae, plotted from TESS data[18]

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] Omicron Andromedae also shows variations with a period of about a day, similar to a β Lyrae-type eclipsing variable, but these are thought to be intrinsic to one of the components and not due to eclipses.[6]

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.[5]

Spectral lines similar to an A2 star are also detectable in the spectrum and these are thought to originate in the B component.[5]

References

  1. 1 2 3 4 5 van Leeuwen, F. (1 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. ISSN 0004-6361. S2CID 18759600.
  2. 1 2 3 Nicolet, B. (1978). "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System". Observatory. Bibcode:1978ppch.book.....N.
  3. 1 2 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. ↑ Slettebak, A (1982). "Spectral types and rotational velocities of the brighter Be stars and A-F type shell stars". Astrophysical Journal Supplement Series. 50: 55. Bibcode:1982ApJS...50...55S. doi:10.1086/190820.
  5. 1 2 3 4 5 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.
  6. 1 2 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. S2CID 17089387.
  7. ↑ Wilson, Ralph Elmer (1953). "General Catalogue of Stellar Radial Velocities". Washington: 0. Bibcode:1953GCRV..C......0W.
  8. 1 2 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.
  9. 1 2 Mitrofanova, A.; Dyachenko, V.; Beskakotov, A.; Balega, Yu.; Maksimov, A.; Rastegaev, D. (2021). "Speckle Interferometry of Nearby Multiple Stars. II. 2007-2020 Positional Measurements and Orbits of Sixteen Objects". The Astronomical Journal. 162 (4): 156. Bibcode:2021AJ....162..156M. doi:10.3847/1538-3881/ac1a78. S2CID 237603742.
  10. 1 2 3 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. Bibcode:2010ARep...54.1134Z. doi:10.1134/S1063772910120061. S2CID 121960504.
  11. 1 2 3 4 5 6 7 8 Tokovinin, Andrei (2018). "The Updated Multiple Star Catalog". The Astrophysical Journal Supplement Series. 235 (1): 6. arXiv:1712.04750. Bibcode:2018ApJS..235....6T. doi:10.3847/1538-4365/aaa1a5. S2CID 119047709.
  12. 1 2 3 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.
  13. 1 2 3 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.
  14. 1 2 3 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. S2CID 118629873.
  15. ↑ "omi And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-06-23.
  16. ↑ Wilson, R. H. (1950). "Observations of double stars". The Astronomical Journal. 55: 153. Bibcode:1950AJ.....55..153W. doi:10.1086/106378.
  17. ↑ 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. S2CID 119115316.
  18. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
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