EZ Canis Majoris
 
| |
| 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] |
| Characteristics | |
| Spectral type | WN4-s[4] |
| U−B color index | −0.89[2] |
| B−V color index | −0.28[2] |
| Variable type | UGZ?[3] |
| Astrometry | |
| 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] |
| Details | |
| Mass | 19[4] M☉ |
| Radius | 2.65[4] R☉ |
| Luminosity (bolometric) | 400,000[4] L☉ |
| Temperature | 89,100[4] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
EZ Canis Majoris (also designated as EZ CMa or WR 6) 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.
References
- 1 2 3 4 Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. Bibcode:2007A&A...474..653V. arXiv:0708.1752
. doi:10.1051/0004-6361:20078357. - 1 2 3 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.
- 1 2 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.
- 1 2 3 4 5 6 7 Hamann, W.-R.; Gräfener, G.; Liermann, A. (2006). "The Galactic WN stars". Astronomy and Astrophysics. 457 (3): 1015. Bibcode:2006A&A...457.1015H. arXiv:astro-ph/0608078 . doi:10.1051/0004-6361:20065052.
- ↑ 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.
- 1 2 Toalá, J. A.; Guerrero, M. A.; Ramos-Larios, G.; Guzmán, V. (2015). "WISE morphological study of Wolf-Rayet nebulae". Astronomy & Astrophysics. 578: A66. Bibcode:2015A&A...578A..66T. ISSN 0004-6361. arXiv:1503.06878 . doi:10.1051/0004-6361/201525706.
- ↑ 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.
- 1 2 The IUE Mega Campaign: Wind Structure and Variability of HD 50896 (WN5) Astrophysical Journal Letters 452 #1, pp. L57 (October 1995) Bibcode: 1995ApJ...452L..57S
External links
- NASA Astronomy Picture of the Day: Sharpless 308 (23 April 2009)
- NASA Astronomy Picture of the Day: Sharpless 308: Star Bubble (23 June 2015)