WR 1
Star in the constellation Cassiopeia
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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[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 |
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]