WR 22

WR 22

WR 22 in the Carina nebula
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Carina
Right ascension 10h 41m 17.51590s[1]
Declination −59° 40′ 36.8957″[1]
Apparent magnitude (V) 6.42[2]
Characteristics
Spectral type WN7h + O9III-V[3]
Apparent magnitude (U) 5.68[2]
Apparent magnitude (B) 6.50[2]
Apparent magnitude (J) 5.705[4]
Apparent magnitude (H) 5.578[4]
Apparent magnitude (K) 5.389[4]
U−B color index −0.82[2]
B−V color index 0.08[2]
J−H color index 0.127[4]
J−K color index 0.316[4]
Variable type Eclipsing binary[5]
Astrometry
Radial velocity (Rv)−28.00[6] km/s
Proper motion (μ) RA: −7.71[1] mas/yr
Dec.: 2.86[1] mas/yr
Parallax (π)0.61 ± 0.52[1] mas
Distance8,200[7] ly
(2,500[7] pc)
Absolute magnitude (MV)−6.73 + −4.44[5]
Orbit[5]
PrimaryWR
CompanionO
Period (P)80.3 days
Semi-major axis (a)34-48 R☉
Eccentricity (e)0.598
Inclination (i)85°
Argument of periastron (ω)
(secondary)		268.2°
Semi-amplitude (K1)
(primary)		70.6 km/s
Semi-amplitude (K2)
(secondary)		190.0 km/s
Details
Mass78[7] + 21[8] M☉
Radius23.7[7] + 9[8] R☉
Luminosity2,000,000[7] + 100,000[8] L☉
Temperature44,700[7] + 34,000[8] K
Age< 4 million years
Database references
SIMBADdata
Other designations
HR 4188, HD 92740, V429 Carinae, HIP 52308

WR 22, also known as V429 Carinae or HR 4188, is a Wolf-Rayet (WR) star in the constellation Carina. It is one of the most massive stars known, as well as one of the most luminous stars, and is also a bright x-ray source due to colliding winds with its less massive O class companion.

Mass

The mass of WR 22 has been determined accurately because it is an eclipsing binary, one of the most massive stars measured in this way rather than by assumptions about stellar evolution.[8]

Evolution

High mass WR stars are young stars only just evolving away from the main sequence, rather than very old stars that have lost all their hydrogen. They show the WR characteristics of strong helium and nitrogen emission because they are strongly convective all the way to the core, so despite probably still burning hydrogen at the core they have dredged up heavier elements to the surface. Just a million or two years ago, WR22 would have been one of the hottest O type main sequence stars.[7]

References

  1. 1 2 3 4 5 Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. 1 2 3 4 5 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. ↑ Gagné, M.; Fehon, G.; Savoy, M. R.; Cartagena, C. A.; Cohen, D. H.; Owocki, S. P. (2012). "An X-Ray Survey of Colliding Wind Binaries". Proceedings of a Scientific Meeting in Honor of Anthony F. J. Moffat held at Auberge du Lac Taureau 465: 301. arXiv:1205.3510. Bibcode:2012ASPC..465..301G.
  4. 1 2 3 4 5 Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; Beichman, C. A.; Carpenter, J. M.; Chester, T.; Cambresy, L.; Evans, T.; Fowler, J.; Gizis, J.; Howard, E.; Huchra, J.; Jarrett, T.; Kopan, E. L.; Kirkpatrick, J. D.; Light, R. M.; Marsh, K. A.; McCallon, H.; Schneider, S.; Stiening, R.; Sykes, M.; Weinberg, M.; Wheaton, W. A.; Wheelock, S.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". VizieR On-line Data Catalog: II/246. Originally published in: 2003yCat.2246....0C 2246. Bibcode:2003yCat.2246....0C.
  5. 1 2 3 Gosset, E.; Nazé, Y.; Sana, H.; Rauw, G.; Vreux, J.-M. (2009). "Phase-resolved XMM-Newton observations of the massive WR+O binary WR 22". Astronomy and Astrophysics 508 (2): 805. Bibcode:2009A&A...508..805G. doi:10.1051/0004-6361/20077981.
  6. ↑ Kharchenko, N. V.; Scholz, R.-D.; Piskunov, A. E.; Röser, S.; Schilbach, E. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten 328 (9): 889. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776.
  7. 1 2 3 4 5 6 7 Gräfener, G.; Hamann, W.-R. (2008). "Mass loss from late-type WN stars and its Z-dependence. Very massive stars approaching the Eddington limit". Astronomy and Astrophysics 482 (3): 945. arXiv:0803.0866. Bibcode:2008A&A...482..945G. doi:10.1051/0004-6361:20066176.
  8. 1 2 3 4 5 Schweickhardt, J.; Schmutz, W.; Stahl, O.; Szeifert, Th.; Wolf, B. (1999). "Revised mass determination of the super massive Wolf-Rayet star WR 22". Astronomy and Astrophysics 347: 127. Bibcode:1999A&A...347..127S.
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