This article is about the star. For the nuclear reactor, see WR-1.
WR 1
A visual bandlight 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.
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.
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.
In 1986, Anthony F. J. Moffat and Michael M. Shara announced their discovery that WR 1 is a variable star.[12] It was given its variable star designation, V863 Cassiopeiae, in 2001.[13] 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.[14] 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
^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.
^ abSamus, 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.
^ abcdefgSota, 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. S2CID104292503.
^ abPyper, 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.
^ abNiedzielski, Andrzej (1998). "The Optical Spectrum of HD 4004 (WN4b). Evidence of Variability". Acta Astronomica. 48: 729. Bibcode:1998AcA....48..729N.
