EZ Canis Majoris

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EZ Canis Majoris
Canis Major constellation map.svg
Red circle.svg

Location of EZ CMa (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Canis Major
Right ascension 06h 54m 13.04410s[1]
Declination −23° 55′ 42.0150″[1]
Apparent magnitude (V) 6.91[2] 6.71 to 6.95[3]
Spectral type WN4-s[4]
U−B color index −0.89[2]
B−V color index −0.28[2]
Variable type UGZ?[3]
Proper motion (μ) RA: −3.76[1] mas/yr
Dec.: 4.35[1] mas/yr
Parallax (π) 1.17 ± 0.57[5] mas
Distance 4,900 ly
(1,500[6] pc)
Absolute magnitude (MV) −4.85[4]
Mass 19[4] M
Radius 2.65[4] R
Luminosity (bolometric) 400,000[4] L
Temperature 89,100[4] K
Other designations
EZ CMa, ALS 98, CD−23°4553, CEL 1426, Collinder 121 4, CPD−23°1588, GC 9061, HD 50896, Hen 3-20, HIP 33165, HR 2583, LBN 1052, MR 6, PPM 251223, SAO 172546, SH 2-308, TYC 6522-3270-1, WR 6
Database references
Detail of one edge of the bubble blown by EZ CMa. EZ CMa is off frame to the left (east).

EZ Canis Majoris (EZ CMa) is a Wolf-Rayet star in the constellation of Canis Major. It is one of the ten brightest Wolf-Rayet stars.[7]

EZ CMa has an apparent visual magnitude which varies between 6.71 and 6.95 over a period of 3.766 days, along with changes in the spectrum.[8] It has been proposed that it could be a binary star, with a neutron star as companion that would complete an orbit around the Wolf-Rayet with that period, being it the cause of those variations. The General Catalogue of Variable Stars lists it as a possible cataclysmic variable on this basis. However it seems more likely that companion does not exist and spectral variations are caused by activity on the star's surface.[8]

The spectral type of WN4 indicates an extremely hot star, and this leads to a very high luminosity, mostly emitted as ultraviolet radiation. The spectrum shows a star entirely devoid of hydrogen at the surface.[4]

EZ CMa is surrounded by a faint bubble nebula, a small HII region blown by stellar winds up to 1,700 km/s and ionised by the intense UV radiation. This is catalogued as Sharpless 308 or just S308.[6] It is likely to be a member of the very scattered open cluster Collinder 121, found around the orange supergiant ο1 CMa.


  1. ^ a b c d Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. arXiv:0708.1752Freely accessible. 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: 0. Bibcode:2002yCat.2237....0D. 
  3. ^ a b 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: 02025. Bibcode:2009yCat....102025S. 
  4. ^ a b c d e f g Hamann, W.-R.; Gräfener, G.; Liermann, A. (2006). "The Galactic WN stars". Astronomy and Astrophysics. 457 (3): 1015. arXiv:astro-ph/0608078Freely accessible. Bibcode:2006A&A...457.1015H. doi:10.1051/0004-6361:20065052. 
  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. ^ a b Toalá, J. A.; Guerrero, M. A.; Ramos-Larios, G.; Guzmán, V. (2015). "WISE morphological study of Wolf-Rayet nebulae". Astronomy & Astrophysics. 578: A66. arXiv:1503.06878Freely accessible. Bibcode:2015A&A...578A..66T. doi:10.1051/0004-6361/201525706. ISSN 0004-6361. 
  7. ^ Van Der Hucht, Karel A. (2001). "The VIIth catalogue of galactic Wolf–Rayet stars". New Astronomy Reviews. 45 (3): 135. Bibcode:2001NewAR..45..135V. doi:10.1016/S1387-6473(00)00112-3. 
  8. ^ a b The IUE Mega Campaign: Wind Structure and Variability of HD 50896 (WN5) Astrophysical Journal Letters 452 #1, pp. L57 (October 1995) Bibcode1995ApJ...452L..57S

External links[edit]