WR 1 is a Wolf-Rayet star located around 10,300 light years away from Earth in the constellation of Cassiopeia. It is only slightly more than twice the size of the sun, but due to a temperature over 100,000 K it is over 758,000 times as luminous as the sun.
 A visual band light curve for V863 Cassiopeiae, adapted from Chené et al. (2008).[1] The data were taken from November 2003 to February 2004, and different cycles are shown with different colors. | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cassiopeia |
| Right ascension | 00h 43m 28.39717s[2] |
| Declination | +64° 45′ 35.3847″[2] |
| Apparent magnitude (V) | 10.54[3] |
| Characteristics | |
| Evolutionary stage | Wolf-Rayet |
| Spectral type | WN4-s[4] |
| U−B color index | −0.24[5] |
| B−V color index | +0.37[5] |
| Variable type | WR[3] |
| Astrometry | |
| Proper motion (μ) | RA: −2.878[2] mas/yr Dec.: −0.702[2] mas/yr |
| Parallax (π) | 0.3092 ± 0.0139 mas[2] |
| Distance | 10,500 ± 500 ly (3,200 ± 100 pc) |
| Absolute magnitude (MV) | −4.9[6] |
| Details | |
| Mass | 27[4] M☉ |
| Radius | 2.26[4] R☉ |
| Luminosity | 760,000[4] L☉ |
| Temperature | 112,200[4] K |
| Rotational velocity (v sin i) | 6.5[7] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
Although WR 1 has been recognised as a Wolf-Rayet star since the 19th century,[8] the WR 1 designation does not indicate that it was the first to be discovered. Ordered by right ascension, WR 1 is the first star in the Seventh Catalogue of galactic Wolf-Rayet stars.[9]
WR 1 is a member of the nitrogen sequence of WR stars and has a spectrum with HeII lines much stronger than HeI lines, and NV emission more than twice the strength of NIII, leading to the assignment of a WN4 spectral type. The spectrum has particularly wide HeII, leading to the equivalent classifications of WN4-b (for broad) or WN4-s (for strong). The spectrum also includes CIV and NIV, but no hydrogen lines at all,[10][11] indicating that WR 1 has already expelled all of its hydrogen through its powerful solar winds.
WR 1 is slightly variable and given the variable star designation V863 Cassiopeiae. The total amplitude of the variations is only 0.09 magnitudes at visual wavelengths. The variations are well-defined with a period of 16.9 days, but the light curve is not sinusoidal and its shape may vary.[12] The variations have been ascribed to a dense asymmetric stellar wind and co-rotating interacting regions in ejected material.[7]
It has been suggested that the variability and an infrared excess could be due to a cool companion, but WR 1 is now considered to be a single star.[11] The WN-b subclass of Wolf-Rayet star are generally thought to be all single, in contrast with the WN-A subclass which have narrow emission on a stronger continuum and are thought to be binary systems with a more conventional hot luminous star.[10]
WR 1 is a possible member of the Cassiopeia OB7 association[9] at a distance of around 1,800 pc,[4] although its Gaia parallax suggests it is more distant.[2] Interstellar extinction is calculated to be 2.1 magnitudes, and at 1,820 pc the bolometric luminosity would be 758,600 L☉. A temperature of 112,200 K is derived from fitting the spectrum, giving a radius of 2.26 R☉.[4]
References
edit- ^ Chené, André-Nicolas; St-Louis, N.; Moffat, A. F. J. (June 2008). "Large-Scale Wind Variability of WR1 (HD 4004); Towards the Rotation Rate of Wolf-Rayet Stars". Mass Loss from Stars and the Evolution of Stellar Clusters ASP Conference Series. 388: 157–158. Bibcode:2008ASPC..388..157C.
- ^ a b c d e f Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ 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. Bibcode:2009yCat....102025S.
- ^ 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". Astronomy & Astrophysics. A57: 625. arXiv:1904.04687. Bibcode:2019A&A...625A..57H. doi:10.1051/0004-6361/201834850. S2CID 104292503.
- ^ a b Pyper, Diane M. (1966). "The Effective Temperatures of Wolf-Rayet Stars as Derived from Their U BV Color Indices Corrected for Emission". Astrophysical Journal. 144: 13. Bibcode:1966ApJ...144...13P. doi:10.1086/148587.
- ^ Crowther, Paul A.; Rate, Gemma (2020). "Unlocking Galactic Wolf–Rayet stars with Gaia DR2 – I. Distances and absolute magnitudes". Monthly Notices of the Royal Astronomical Society. 493 (1): 1512–1529. arXiv:1912.10125. Bibcode:2020MNRAS.493.1512R. doi:10.1093/mnras/stz3614. S2CID 209444955.
- ^ a b St-Louis, N. (2013). "Revealing the Asymmetry of the Wind of the Variable Wolf-Rayet Star WR1 (HD 4004) through Spectropolarization". The Astrophysical Journal. 777 (1): 9. arXiv:1308.5914. Bibcode:2013ApJ...777....9S. doi:10.1088/0004-637X/777/1/9. S2CID 118553289.
- ^ Campbell, W. W. (1894). "The Wolf-Rayet stars". Astronomy and Astro-Physics. 13: 448. Bibcode:1894AstAp..13..448C.
- ^ a b 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. S2CID 121477300.
- ^ a b Smith, Lindsey F.; Shara, Michael M.; Moffat, Anthony F. J. (1996). "A three-dimensional classification for WN stars". Monthly Notices of the Royal Astronomical Society. 281 (1): 163–191. Bibcode:1996MNRAS.281..163S. doi:10.1093/mnras/281.1.163.
- ^ a b Niedzielski, Andrzej (1998). "The Optical Spectrum of HD 4004 (WN4b). Evidence of Variability". Acta Astronomica. 48: 729. Bibcode:1998AcA....48..729N.
- ^ Chené, A.-N.; St-Louis, N. (2010). "Large-scale Periodic Variability of the Wind of the Wolf-Rayet Star WR 1 (HD 4004)". The Astrophysical Journal. 716 (2): 929. arXiv:1004.4893. Bibcode:2010ApJ...716..929C. doi:10.1088/0004-637X/716/2/929. S2CID 118870393.