V636 Scorpii

V636 Scorpii is a multiple star system in the constellation Scorpius, 3,000 light years away. The primary is a Classical Cepheid (δ Cephei) variable and its visual magnitude varies from 6.4 to 6.9.

V636 Sco
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius
Right ascension  17h 22m 46.47796s[1]
Declination −45° 36′ 51.3868″[1]
Apparent magnitude (V) 6.40 - 6.92[2]
Characteristics
Cepheid
Spectral type F7/8Ib/II-G5[2]
Variable type δ Cep[2]
companion
Spectral type B9.5V[3]
Astrometry
Radial velocity (Rv)9.09 ± 0.17[4] km/s
Proper motion (μ) RA: -3.05 ± 1.03[1] mas/yr
Dec.: -2.40 ± 0.38[1] mas/yr
Parallax (π)1.15 ± 0.76[1] mas
Distanceapprox. 3,000 ly
(approx. 900 pc)
Absolute magnitude (MV)-3.64[3]
Orbit
Period (P)1,318 days[3]
Semi-major axis (a)6.7[3]
Eccentricity (e)0.26[5]
Details
Cepheid
Mass5.6[3] M☉
Radius~50[6] R☉
Luminosity2,500[3] L☉
Metallicity+0.07[7]
companion
Mass2.4 M☉
Other designations
V636 Sco, HIP 85035, CD−45°11441, HD 156979, SAO 227880
Database references
SIMBADdata

V636 Scorpii is a spectroscopic binary, and the fainter companion is thought to itself consist of two stars. The primary is a luminous yellow star and a δ Cephei variable. The less massive companion orbits every 3.6 years and is apparently a B9.5 main sequence star, but the dynamics of the system suggest that it may actually be a pair of stars is a close orbit.[8]

The Cepheid primary pulsates regularly with a period of 6.79671 days. It is a yellow-white supergiant or bright giant that is 5.6 times as massive as the Sun and 2,500 times as luminous.[3]

References
  1. Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. 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.
  3. Evans, Nancy Remage; Bond, Howard E.; Schaefer, Gail H.; Mason, Brian D.; Karovska, Margarita; Tingle, Evan (2013). "Binary Cepheids: Separations and Mass Ratios in 5M ⊙ Binaries". Astronomical Journal. 146 (4): 93, 10 pp. arXiv:1307.7123v1. Bibcode:2013AJ....146...93E. doi:10.1088/0004-6256/146/4/93.
  4. 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.
  5. Evans, Nancy Remage; Carpenter, Kenneth G.; Robinson, Richard; Kienzle, Francesco; Dekas, Anne E. (2005). "High-Mass Triple Systems: The Classical Cepheid Y Carinae". The Astronomical Journal. 130 (2): 789. arXiv:astro-ph/0504169. Bibcode:2005AJ....130..789E. doi:10.1086/430458.
  6. Moskalik, P.; Gorynya, N. A. (2005). "Mean Angular Diameters and Angular Diameter Amplitudes of Bright Cepheids". Acta Astronomica. 55: 247. arXiv:astro-ph/0507076. Bibcode:2005AcA....55..247M.
  7. Marsakov, V. A.; Koval', V. V.; Kovtyukh, V. V.; Mishenina, T. V. (2013). "Properties of the population of classical Cepheids in the Galaxy". Astronomy Letters. 39 (12): 851. Bibcode:2013AstL...39..851M. doi:10.1134/S1063773713120050.
  8. Böhm-Vitense, E.; Evans, N. R.; Carpenter, K.; Albrow, Michael D.; Cottrell, P. L.; Robinson, R.; Beck-Winchatz, B. (1998). "The Mass of the Cepheid Binary V636 Scorpii". The Astrophysical Journal. 505 (2): 903. Bibcode:1998ApJ...505..903B. doi:10.1086/306177.
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