HD 93205

HD 93205, or V560 Carinae, is a binary stellar system, in the Carina Nebula (NGC 3372) in the constellation Carina. It consists of two massive O-stars that revolve around each other in 6 days.

HD 93205
Observation data
Epoch J2000      Equinox J2000
Constellation Carina
Right ascension  10h 44m 33.740s[1]
Declination −59° 44′ 15.46″[1]
Apparent magnitude (V) 7.75[2]
Characteristics
Spectral type O3.5Vf + O8V[3]
U−B color index −0.91[2]
B−V color index +0.05[2]
Variable type Ellipsoidal[4]
Astrometry
Radial velocity (Rv)3.6 km/s
Proper motion (μ) RA: −6.7[1] mas/yr
Dec.: 1.2[1] mas/yr
Absolute magnitude (MV)−5.87 + −4.32[5]
Orbit[6]
Period (P)6.0803 days
Eccentricity (e)0.370
Inclination (i)60[7]°
Semi-amplitude (K1)
(primary)		132.6 km/s
Semi-amplitude (K2)
(secondary)		313.6 km/s
Details
Mass40 - 60[6] M☉
Radius9.2[7] R☉
Luminosity1,160,000[5] L☉
Temperature51,300[5] K
secondary
Mass17 - 25.3[6] M☉
Radius7.0[7] R☉
Luminosity112,000[5] L☉
Temperature38,000[5] K
Age< 2[6] Myr
Other designations
V560 Car, CD−59° 3294, HD 93205, SAO 238418
Database references
SIMBADdata

The more massive member of the pair is an O3.5 main sequence star. The spectrum shows some ionised nitrogen and helium emission lines, indicating some mixing of fusion products to the surface and a strong stellar wind. The mass calculated from apsidal motion of the orbits is 40 to 60 M☉. This is somewhat lower than expected from evolutionary modelling of a star with its observed parameters.[6]

The less massive member is an O8 main sequence star of approximately 20 M☉.[7] It moves in its orbit at a speed of over 300 km/s and is considered to be a relativistic binary, which causes the apses of the orbit to change in a predictable way.[5]

The closeness of the two stars causes them to become deformed, and this means that the observed brightness of the system varies slightly every six days during its orbit. The total amplitude of the variation is only 0.02 magnitudes.[4]

Among its neighbors are some of the most massive and luminous stars in the galaxy, like Eta Carinae, HD 93250 and the binary HD 93129.

References
  1. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862.
  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. Sota, A.; Maíz Apellániz, J.; Morrell, N. I.; Barbá, R. H.; Walborn, N. R.; Gamen, R. C.; Arias, J. I.; Alfaro, E. J. (2014). "The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright Southern Stars". The Astrophysical Journal Supplement Series. 211 (1): 84. arXiv:1312.6222. Bibcode:2014ApJS..211...10S. doi:10.1088/0067-0049/211/1/10. 10.
  4. 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.
  5. Morrell, N. I.; Barbá, R. H.; Niemela, V. S.; Corti, M. A.; Albacete Colombo, J. F.; Rauw, G.; Corcoran, M.; Morel, T.; Bertrand, J.-F.; Moffat, A. F. J.; St-Louis, N. (2001). "Optical spectroscopy of X-Mega targets - II. The massive double-lined O-type binary HD 93205" (PDF). Monthly Notices of the Royal Astronomical Society. 326: 85–94. arXiv:astro-ph/0105014. Bibcode:2001MNRAS.326...85M. doi:10.1046/j.1365-8711.2001.04500.x.
  6. Benvenuto, O. G.; Serenelli, A. M.; Althaus, L. G.; Barbá, R. H.; Morrell, N. I. (2002). "Calculation of the masses of the binary star HD 93205 by application of the theory of apsidal motion". Monthly Notices of the Royal Astronomical Society. 330 (2): 435–442. arXiv:astro-ph/0110662. Bibcode:2002MNRAS.330..435B. doi:10.1046/j.1365-8711.2002.05083.x.
  7. Antokhina; et al. (2000). "Light Curve Solution of HD 93205 (O3 V + O8 V) Containing the Earliest Known Star in a Well-studied Binary". The Astrophysical Journal. 529 (1): 463–476. Bibcode:2000ApJ...529..463A. doi:10.1086/308228.
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