WR 93b

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WR 93b
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Scorpius
Right ascension  17h 32m 03.31s[1]
Declination −35° 04′ 32.4″[1]
Evolutionary stage Wolf-Rayet star
Spectral type WO3[2]
Apparent magnitude (B) 16.9[1]
Apparent magnitude (R) 14.4[1]
Apparent magnitude (J) 11.331[1]
Apparent magnitude (K) 10.17[3]
Proper motion (μ) RA: −0.579±0.096[4] mas/yr
Dec.: −2.171±0.075[4] mas/yr
Parallax (π)0.3735 ± 0.0658[4] mas
Distanceapprox. 9,000 ly
(approx. 2,700 pc)
[5] M
Radius0.44[5] R
[5] L
Temperature160,000[2] K
Other designations
2MASS J17320330-3504323, SSTGLMC G353.2744-00.8460
Database references

WR 93b is a Wolf-Rayet star in the constellation Scorpius, an extremely rare star on the WO oxygen sequence.


WR 93b was discovered in 2003 during a study of emission line stars from the AAO/UKST Southern Galactic Plane Survey. It was published as the fourth galactic WO class star in 1994.[6] This was too late to be included in the VIIth Wolf Rayet catalogue,[7] but it is listed in an annex published in 2006.[3]

It lies in the direction of the galactic centre and is thought to be part of the Scutum-Crux spiral arm. It is highly reddened and Interstellar extinction causes it to be 6.5 magnitudes fainter at visual wavelengths.[6]


WR 93b, of spectral classification WO3, is one of the very few known oxygen-sequence Wolf-Rayet stars, just four in the Milky Way galaxy and five in external galaxies. Modelling the atmosphere gives a luminosity around 200,000 L. It is a very small dense star, with a radius less than the sun's but with a mass nearly 10 solar masses. Very strong stellar winds, with a terminal velocity of 5,000 kilometers per second are causing WR 93b to lose 10−5 M/year.[2] For comparison, the Sun loses (2-3) x 10−14 solar masses per year due to its solar wind, several hundred million times less than WR 93b.

Evolutionary status[edit]

WO Wolf-Rayet stars are the last evolutionary stage of the most massive stars before exploding as supernovae, possibly with a gamma-ray burst.[8] It is very likely that WR 93b is on its last stages of nuclear fusion, near or beyond the end of helium burning.[9] It has been calculated that WR 93b will explode as a supernova within 8,000 years.[2]

See also[edit]


  1. ^ a b c d e 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.
  2. ^ a b c d Tramper, F.; Straal, S. M.; Sanyal, D.; Sana, H.; de Koter, A.; Gräfener, G.; Langer, N.; Vink, J. S.; de Mink, S. E.; Kaper, L. (2015). "Massive stars on the verge of exploding: The properties of oxygen sequence Wolf-Rayet stars". Astronomy & Astrophysics. 581 (110): A110. arXiv:1507.00839v1. Bibcode:2015A&A...581A.110T. doi:10.1051/0004-6361/201425390.
  3. ^ a b Van Der Hucht, K. A. (2006). "New Galactic Wolf-Rayet stars, and candidates. An annex to the VIIth Catalogue of Galactic Wolf-Rayet Stars". Astronomy and Astrophysics. 458 (2): 453–459. arXiv:astro-ph/0609008. Bibcode:2006A&A...458..453V. doi:10.1051/0004-6361:20065819.
  4. ^ 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.
  5. ^ a b c Sander, A.; Hamann, W.-R.; Todt, H. (2012). "The Galactic WC stars. Stellar parameters from spectral analyses indicate a new evolutionary sequence". Astronomy & Astrophysics. 540: A144. arXiv:1201.6354. Bibcode:2012A&A...540A.144S. doi:10.1051/0004-6361/201117830.
  6. ^ a b Drew, Janet E.; Barlow, M. J.; Unruh, Y. C.; Parker, Q. A.; Wesson, R.; Pierce, M. J.; Masheder, M. R. W.; Phillipps, S. (2004). "Discovery of a WO star in the Scutum-Crux arm of the inner Galaxy". Monthly Notices of the Royal Astronomical Society. 351 (1): 206–214. arXiv:astro-ph/0403482. Bibcode:2004MNRAS.351..206D. doi:10.1111/j.1365-2966.2004.07771.x.
  7. ^ van der Hucht, Karel A. (2001). "The VIIth catalogue of galactic Wolf–Rayet stars". New Astronomy Reviews. 45 (3): 135–232. Bibcode:2001NewAR..45..135V. doi:10.1016/S1387-6473(00)00112-3. ISSN 1387-6473.
  8. ^ Groh, Jose H.; Meynet, Georges; Georgy, Cyril; Ekstrom, Sylvia (2013). "Fundamental properties of core-collapse Supernova and GRB progenitors: Predicting the look of massive stars before death". Astronomy & Astrophysics. 558: A131. arXiv:1308.4681. Bibcode:2013A&A...558A.131G. doi:10.1051/0004-6361/201321906.
  9. ^ Groh, Jose (2014). "The evolution of massive stars and their spectra I. A non-rotating 60 Msun star from the zero-age main sequence to the pre-supernova stage". Astronomy & Astrophysics. 564: A30. arXiv:1401.7322. Bibcode:2014A&A...564A..30G. doi:10.1051/0004-6361/201322573.

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