AO Cassiopeiae

AO Cassiopeiae, also known as Pearce's Star, is a binary system composed of an O8 main sequence star and an O9.2 bright giant that respectively weigh anywhere between 20.30 and 57.75 times and 14.8 and 31.73 times the mass of the Sun.[10]

AO Cas
Location of AO Cas (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Cassiopeia
Right ascension  00h 17m 43.062s[1]
Declination +51° 25′ 59.12″[1]
Apparent magnitude (V) 6.14[2] (6.07-6.24[3])
Characteristics
Spectral type O8V((f)) + O9.2II[4]
U−B color index −0.97[2]
B−V color index −0.13[2]
Variable type Eclipsing Variable star[3]
Astrometry
Radial velocity (Rv)−31.10[5] km/s
Proper motion (μ) RA: −3.98 ± 0.35[1] mas/yr
Dec.: −1.76 ± 0.29[1] mas/yr
Parallax (π)1.36 ± 0.44[1] mas
Distanceapprox. 2,400 ly
(approx. 700 pc)
Absolute magnitude (MV)−[6]
Orbit[7]
Period (P)3.52348 days
Semi-major axis (a)28.57 R☉
Eccentricity (e)0
Inclination (i)65.7°
Longitude of the node (Ω)3.10°
Semi-amplitude (K1)
(primary)		143.7 km/s
Semi-amplitude (K2)
(secondary)		230.6 km/s
Details[7]
II
Mass9.65 M☉
Radius9.43 R☉
Luminosity115,000[8] L☉
Surface gravity (log g)3.45 cgs
Temperature29,239 K
Rotational velocity (v sin i)120[8] km/s
V
Mass15.59 M☉
Radius4.61 R☉
Luminosity66,000[8] L☉
Surface gravity (log g)4.30 cgs
Temperature33,675 K
Rotational velocity (v sin i)130[8] km/s
Other designations
Pearce's Star,[9] AO Cas, HR 65, BD+50°46, HD 1337, SAO 21273, HIP 1415
Database references
SIMBADdata

The AO Cas system is an eclipsing binary with a period of roughly 3.5 days, with the apparent magnitude ranging between 6.07 and 6.24.[11] Stars of this brightness are generally just visible to the unaided eye in dark skies in semirural locations.[12] The component stars are so close to each other they are ellipsoidal (egg-shaped).[13] AO Cas is considered a contact binary, with both stars at or near their Roche lobes.[3]

References
  1. van Leeuwen, F. (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.Vizier catalog entry
  2. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  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. Bibcode:2009yCat....102025S.
  4. Sota, A.; Maíz Apellániz, J.; Walborn, N. R.; Alfaro, E. J.; Barbá, R. H.; Morrell, N. I.; Gamen, R. C.; Arias, J. I. (2011). "The Galactic O-Star Spectroscopic Survey. I. Classification System and Bright Northern Stars in the Blue-violet at R ~ 2500". The Astrophysical Journal Supplement. 193 (2): 24. arXiv:1101.4002. Bibcode:2011ApJS..193...24S. doi:10.1088/0067-0049/193/2/24.
  5. Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; Levato, H.; Morrell, N. I.; Torres, G.; Udry, S. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics. 424 (2): 727. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213.
  6. Conti, Peter S.; Alschuler, William R. (1971). "Spectroscopic Studies of O-Type Stars. I. Classification and Absolute Magnitudes". Astrophysical Journal. 170: 325. Bibcode:1971ApJ...170..325C. doi:10.1086/151218.
  7. Palate, M.; Rauw, G. (2012). "Spectral modelling of circular massive binary systems. Towards an understanding of the Struve-Sahade effect?". Astronomy & Astrophysics. 537: A119. arXiv:1109.1103. Bibcode:2012A&A...537A.119P. doi:10.1051/0004-6361/201117520.
  8. Bagnuolo, W. G.; Gies, D. R. (1992). "Tomographic Separation of Composite Spectra of O-Type Stars". Complementary Approaches to Double and Multiple Star Research. 32: 140. Bibcode:1992ASPC...32..140B.
  9. Struve, O.; Rudkjøbing, M. (1948). "A Note on the Spectrum of HD 698 (j. A. Pearce's Star of Large Mass)". Astrophysical Journal. 108: 537. Bibcode:1948ApJ...108R.537S. doi:10.1086/145098.
  10. Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355
  11. Watson, Christopher (4 January 2010). "AO Cassiopeiae". AAVSO Website. American Association of Variable Star Observers. Retrieved 15 February 2014.
  12. Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Retrieved 5 February 2014.
  13. Astronomy and Cosmogony. CUP Archive. pp. 125–. GGKEY:KFJRG3PWW14.
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