WR 3

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WR 3
Observation data
Epoch 2000      Equinox 2000
Constellation Cassiopeia
Right ascension  00h 43m 28.39827s[1]
Declination +64° 45′ 35.4011″[1]
Apparent magnitude (V) 10.69[2]
Evolutionary stage Wolf-Rayet
Spectral type WN3-hw[3]
U−B color index −0.86[2]
B−V color index +0.02[2]
Radial velocity (Rv)100.00[4] km/s
Proper motion (μ) RA: −4.061±0.063[5] mas/yr
Dec.: −1.422±0.072[5] mas/yr
Parallax (π)0.3131 ± 0.0412[5] mas
Distanceapprox. 10,000 ly
(approx. 3,200 pc)
Absolute magnitude (MV)−3.13[3]
Mass15[3] M
Radius2.48[3] R
Luminosity363,000[3] L
Temperature89,100[3] K
Other designations
HD 9974, WR 3, HIP 7681, 2MASS J01385562+5809227
Database references

WR 3 is a Wolf-Rayet star located around 16,000 light years away from Earth in the constellation of Cassiopeia.

WR 3 is a member of the nitrogen sequence of WR stars and has a spectrum with strong HeII and NV lines, but weak NIV. HeI lines are very weak or missing, but there are lines of OVI. Unusually, there are lines of hydrogen and absorption components in many lines creating P Cygni profiles. Overall, the emission is weaker than stars of similar spectral type, and it has often been suggested that WR 3 has a type O binary companion. However, there are no other signs of a companion and it is thought to be a single star with a spectral type of WN3-hw. The "h" and "w" indicate that hydrogen is present and the emission is weaker for the class.[6][7]

Ordered by right ascension, WR 3 was the third star in the Sixth Catalogue of galactic Wolf-Rayet stars. WR 1 and WR 2 are also both early WN stars in Cassiopeiae.[8]

WR 3 is a massive and luminous star. The presence of hydrogen in its spectrum suggests that it is younger than hydrogen-free WR stars and may still be fusing hydrogen in its core. The emission lines of heavy elements in its spectrum are produced by strong convection and powerful stellar winds rather than complete loss of the outer layers of the star.[9] The wind has been measured at 2,700 km/s leading to mass being lost at four millionths M per year.[3]


  1. ^ a b 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. ^ a b c 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. ^ a b c d e f g 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". arXiv:1904.04687 [astro-ph.SR].
  4. ^ 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. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776.
  5. ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  6. ^ Hiltner, W. A.; Schild, R. E. (1966). "Spectral Classification of Wolf-Rayet Stars". Astrophysical Journal. 143: 770. Bibcode:1966ApJ...143..770H. doi:10.1086/148556.
  7. ^ Marchenko, S. V.; Moffat, A. F. J.; Crowther, P. A.; Chené, A.-N.; De Serres, M.; Eenens, P. R. J.; Hill, G. M.; Moran, J.; Morel, T. (2004). "Hydrogen in the atmosphere of the evolved WN3 Wolf-Rayet star WR 3: Defying an evolutionary paradigm?" (PDF). Monthly Notices of the Royal Astronomical Society. 353: 153. Bibcode:2004MNRAS.353..153M. doi:10.1111/j.1365-2966.2004.08058.x.
  8. ^ Van Der Hucht, Karel A.; Conti, Peter S.; Lundström, Ingemar; Stenholm, Björn (1981). "The Sixth Catalogue of galactic Wolf-Rayet stars, their past and present". Space Science Reviews. 28 (3): 227–306. Bibcode:1981SSRv...28..227V. doi:10.1007/BF00173260.
  9. ^ Smith, Nathan; Conti, Peter S. (2008). "On the Role of the WNH Phase in the Evolution of Very Massive Stars: Enabling the LBV Instability with Feedback". The Astrophysical Journal. 679 (2): 1467–1477. arXiv:0802.1742. Bibcode:2008ApJ...679.1467S. doi:10.1086/586885.