WR 1

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WR 1
V863CasLightCurve.png
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 [2]
Right ascension 00h 43m 28.39717s [3]
Declination +64° 45′ 35.3847″ [3]
Apparent magnitude  (V)10.54 [4]
Characteristics
Evolutionary stage Wolf-Rayet
Spectral type WN4-s [5]
U−B color index −0.24 [6]
B−V color index +0.37 [6]
Variable type WR [4]
Astrometry
Proper motion (μ)RA: −2.878 [3] mas/yr
Dec.: −0.702 [3] mas/yr
Parallax (π)0.3092±0.0139  mas [3]
Distance 10,500 ± 500  ly
(3,200 ± 100  pc)
Absolute magnitude  (MV)−4.9 [7]
Details
Mass 27 [5]   M☉
Radius 2.26 [5]   R☉
Luminosity 760,000 [5]   L☉
Temperature 112,200 [5]   K
Rotational velocity (v sin i)6.5 [8]  km/s
Other designations
V863 Cas, BD+63°83, HD 4004, HIP 3415
Database references
SIMBAD data

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, [9] 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. [10]

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, [11] [12] 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. [13] It was given its variable star designation, V863 Cassiopeiae, in 2001. [14] 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. [15] The variations have been ascribed to a dense asymmetric stellar wind and co-rotating interacting regions in ejected material. [8]

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. [12] 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. [11]

WR 1 is a possible member of the Cassiopeia OB7 association [10] at a distance of around 1,800  pc , [5] although its Gaia parallax suggests it is more distant. [3] 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☉. [5]

References

  1. ↑ 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.
  2. ↑ Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv: 1108.4971 . Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN   1562-6873. ISSN   1063-7737. S2CID   119257644.
  3. 1 2 3 4 5 6 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.
  4. 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. Bibcode:2009yCat....102025S.
  5. 1 2 3 4 5 6 7 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.
  6. 1 2 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.
  7. ↑ 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.
  8. 1 2 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.
  9. ↑ Campbell, W. W. (1894). "The Wolf-Rayet stars". Astronomy and Astro-Physics. 13: 448. Bibcode:1894AstAp..13..448C.
  10. 1 2 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.
  11. 1 2 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 .
  12. 1 2 Niedzielski, Andrzej (1998). "The Optical Spectrum of HD 4004 (WN4b). Evidence of Variability". Acta Astronomica. 48: 729. Bibcode:1998AcA....48..729N.
  13. ↑ Moffat, A. F. J.; Shara, M. M. (October 1986). "Photometric variability of a complete sample of northern Wolf-Rayet stars". Astronomical Journal. 92: 952–975. Bibcode:1986AJ.....92..952M. doi:10.1086/114227.
  14. ↑ Kazarovets, E. V.; Samus, N. N.; Durlevich, O. V. (July 2001). "The 76th Name-List of Variable Stars" (PDF). Information Bulletin on Variable Stars. 5135: 1–67. Bibcode:2001IBVS.5135....1K . Retrieved 14 January 2025.
  15. ↑ 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.
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