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.
  | |
| 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] |
| Distance | approx. 690 ly (approx. 210 pc) |
| Absolute magnitude (MV) | −2.6[8] |
| Orbit[9] | |
| Primary | A |
| Companion | B |
| Period (P) | 118.0 yr |
| Semi-major axis (a) | 0.304″ |
| Eccentricity (e) | 0.340 |
| Inclination (i) | 107.4° |
| Orbit[10][11] | |
| Primary | Aa |
| Companion | Ab |
| Period (P) | 5.6 yr |
| Semi-major axis (a) | 0.061″ |
| Eccentricity (e) | 0.22 |
| Inclination (i) | 152.0° |
| Orbit[12][11] | |
| Primary | Ba |
| Companion | Bb |
| 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 | |
| Mass | 9.85[11] M☉ |
| Radius | 6.6[8] R☉ |
| Luminosity | 1,380[13] L☉ |
| Temperature | 13,800[13] K |
| Rotational velocity (v sin i) | 240[13] km/s |
| ο And Ab | |
| Mass | 4.51[11] M☉ |
| ο And Ba | |
| Mass | 3.74[11] M☉ |
| ο And Bb | |
| Mass | 2.86[11] M☉ |
| Age | 50.1 ± 6.8[14] Myr |
| Other designations | |
| ο And A: HD 217675 | |
| ο And B: HD 217676 | |
| Database references | |
| SIMBAD | data |
System edit
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 edit
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 edit
- ^ a b c d e 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.
- ^ a b c Nicolet, B. (1978). "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System". Observatory. Bibcode:1978ppch.book.....N.
- ^ a b c 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.
- ^ 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.
- ^ 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.
- ^ a b 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.
- ^ Wilson, Ralph Elmer (1953). "General Catalogue of Stellar Radial Velocities". Washington: 0. Bibcode:1953GCRV..C......0W.
- ^ 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.
- ^ a b 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.
- ^ a b c 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.
- ^ a b c d e f g h 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.
- ^ a b c 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.
- ^ 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.
- ^ a b c 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.
- ^ "omi And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-06-23.
- ^ Wilson, R. H. (1950). "Observations of double stars". The Astronomical Journal. 55: 153. Bibcode:1950AJ.....55..153W. doi:10.1086/106378.
- ^ 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.
- ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.