HD 56925
.jpg) WR7 at the centre of NGC 2359 | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Canis Major |
| Right ascension | 07h 18m 29.1316s[1] |
| Declination | −13° 13′ 01.507″[1] |
| Apparent magnitude (V) | 11.4 |
| Characteristics | |
| Spectral type | WN4-s[2] |
| U−B color index | -0.47[3] |
| B−V color index | 0.28[3] |
| Variable type | None |
| Astrometry | |
| Proper motion (μ) | RA: -3.74[1] mas/yr Dec.: 3.52[1] mas/yr |
| Parallax (π) | -0.66 ± 2.55 mas |
| Distance | 3,670[4] pc |
| Absolute magnitude (MV) | -3.84[2] |
| Details | |
| Mass | 16[2] M☉ |
| Radius | 1.41[2] R☉ |
| Luminosity | 280,000[2] L☉ |
| Temperature | 112,000[2] K |
| Age | 20 million years |
| Other designations | |
| Database references | |
| SIMBAD | data |
WR 7 or HD 56925/HIP 35 378 is a Wolf-Rayet star at the centre of the nebula NGC 2359 (also known as the Thor's Helmet Nebula) in the constellation of Canis Major.
The distance is uncertain, with estimates between 3.5 kiloparsecs (11,410 lightyears) and 6.9 kiloparsecs (22,500 light years). Assuming a distance of 4.8 kiloparsecs (15,600 light-years), this star is calculated to be 280.000 times brighter than our Sun, 16 times more massive, and 1.41 times larger with a surface temperature of 112,000 Kelvin.
Stars of its kind are characterised by a rapid loss of stellar mass, driven by chemically enriched high-speed stellar winds. It is estimated that it loses mass at the rate of 7x10−5 solar masses each year through winds of 1,545 km/s.[5]
The ring nebula NGC 2359 is excited by the ionising radiation of WR7. The ring is approximately 4pc across and prominent at wavelengths from radio to x-ray.[5][6]
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. doi:10.1051/0004-6361:20078357.
- 1 2 3 4 5 6 Hamann, W. -R.; Gräfener, G.; Liermann, A. (2006). "The Galactic WN stars". Astronomy and Astrophysics 457 (3): 1015. arXiv:astro-ph/0608078. Bibcode:2006A&A...457.1015H. doi:10.1051/0004-6361:20065052.
- 1 2 Reed, B. Cameron (1998). "UBVβ Database for Case-Hamburg Northern and Southern Luminous Stars". The Astrophysical Journal Supplement Series 115 (2): 271. Bibcode:1998ApJS..115..271R. doi:10.1086/313088.
- ↑ Toalá, J. A.; Guerrero, M. A.; Chu, Y.-H.; Gruendl, R. A. (2015). "On the diffuse X-ray emission from the Wolf-Rayet bubble NGC 2359". Monthly Notices of the Royal Astronomical Society 446: 1083. Bibcode:2015MNRAS.446.1083T. doi:10.1093/mnras/stu2163.
- 1 2 Cappa, C. E.; Goss, W. M.; Niemela, V. S.; Ostrov, P. G. (1999). "A Study of Neutral and Ionized Gas of the Wolf-Rayet Ring Nebula NGC 2359". The Astronomical Journal 118 (2): 948. Bibcode:1999AJ....118..948C. doi:10.1086/300995.
- ↑ Zhekov, S. A. (2014). "X-rays from wind-blown bubbles: An XMM-Newton detection of NGC 2359". Monthly Notices of the Royal Astronomical Society 443: 12. Bibcode:2014MNRAS.443...12Z. doi:10.1093/mnras/stu1138.
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