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
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