WR 12

WR 12 (V378 Velorum) is a spectroscopic binary in the constellation Vela. It is an eclipsing binary consisting of a Wolf-Rayet star and a luminous companion of unknown spectral type. The primary is one of the most luminous stars known.

WR 12
Observation data
Epoch J2000      Equinox J2000
Constellation Vela
Right ascension 08h 44m 47.293s[1]
Declination –45° 58′ 55.46″[1]
Apparent magnitude (V) 10.78[2]
Characteristics
Spectral type WN8h[3]
U−B color index –0.39[2]
B−V color index +0.56[2]
Variable type Algol + WR[4]
Astrometry
Proper motion (μ) RA: –3.1[1] mas/yr
Dec.: +4.6[1] mas/yr
Parallax (π)0.31 ± 0.26[5] mas
Distance5,710+1,240
−920[6] pc
Absolute magnitude (MV)–6.68[3] (–6.5 + –5.5[7])
Orbit[8]
PrimaryWR
CompanionO
Period (P)23.92336 ± 0.00001 days
Eccentricity (e)0
Inclination (i)78.8[7]°
Periastron epoch (T)2,449,811.188 ± 0.065
Semi-amplitude (K1)
(primary)		141.9 ± 2.2 km/s
Details[3]
WR
Mass30 M☉
Radius16.38 R☉
Luminosity (bolometric)851,000[6] L☉
Temperature44,700 K
Other designations
WR 12, V378 Velorum, CD−45°4482, 2MASS J08444729-4558554, Hen 3-200
Database references
SIMBADdata

The spectrum of WR 12 is dominated by the broad emission lines of the primary Wolf-Rayet star. The lowest ionisation nitrogen emission lines are strongest, with NV lines being very weak. The HeI lines are stronger than the HeII lines. Unusually the hydrogen emission is stronger still, leading to a WN8h spectral class. CIV emission is almost undetectable.[9] It has been suggested that the companion is a class O star, but its lines cannot be seen in the spectrum.[7]

The system produces eclipses which dim the brightness of the star by 0.12 magnitudes every 24 days. The stars are detached and so it is classified as an Algol-type eclipsing binary. The inclination of the orbit has been estimated at 78.8° but a full orbital solution is not available because the secondary cannot be directly detected.[4][7]

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.
  2. Moffat, A. F. J.; Vogt, N. (1975). "Southern open star clusters IV. UBV-Hbeta photometry of 26 clusters from Monoceros to Vela". Astronomy and Astrophysics. 20: 85. Bibcode:1975A&AS...20...85M.
  3. Sota, A.; Maíz Apellániz, J.; Morrell, N. I.; Barbá, R. H.; Walborn, N. R.; Gamen, R. C.; Arias, J. I.; Alfaro, E. J.; Oskinova, L. M. (2019). "The Galactic WN stars revisited. Impact of Gaia distances on fundamental stellar parameters". Astronomy & Astrophysics. A57: 625. arXiv:1904.04687. doi:10.1051/0004-6361/201834850. S2CID 104292503.
  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. Gaia Collaboration (2016). "VizieR Online Data Catalog: Gaia DR1 (Gaia Collaboration, 2016)". VizieR On-line Data Catalog: I/337. Originally Published in: Astron. Astrophys. 1337. Bibcode:2016yCat.1337....0G.
  6. Crowther, Paul A.; Rate, Gemma (2020). "Unlocking Galactic Wolf–Rayet stars with Gaia DR2 – I. Distances and absolute magnitudes". Monthly Notices of the Royal Astronomical Society. 493 (1): 1512–1529. arXiv:1912.10125. Bibcode:2020MNRAS.493.1512R. doi:10.1093/mnras/stz3614. S2CID 209444955.
  7. Lamontagne, Robert; Moffat, Anthony F. J.; Drissen, Laurent; Robert, Carmelle; Matthews, Jaymie M. (1996). "Photometric Determination of Orbital Inclinations and Mass Loss Rates for Wolf-Rayet Stars in WR+O Binaries". Astronomical Journal. 112: 2227. Bibcode:1996AJ....112.2227L. doi:10.1086/118175.
  8. Fahed, R.; Moffat, A. F. J. (2012). "Colliding winds in five WR+O systems of the Southern hemisphere". Monthly Notices of the Royal Astronomical Society. 424 (3): 1601. Bibcode:2012MNRAS.424.1601F. doi:10.1111/j.1365-2966.2012.20494.x.
  9. Smith, Lindsey F.; Shara, Michael M.; Moffat, Anthony F. J. (1996). "A three-dimensional classification for WN stars". Monthly Notices of the Royal Astronomical Society. 281 (1): 163–191. Bibcode:1996MNRAS.281..163S. doi:10.1093/mnras/281.1.163.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.