WR 93b
Wolf-Rayet star in the constellation of Scorpius
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WR 93b is a Wolf-Rayet star in the constellation Scorpius, an extremely rare star on the WO oxygen sequence. It appears near NGC 6357 in the tail of the scorpion.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 17h 32m 03.308s[1] |
| Declination | −35° 04′ 32.62″[1] |
| Apparent magnitude (V) | 15.2[2] |
| Characteristics | |
| Evolutionary stage | Wolf-Rayet star |
| Spectral type | WO3[3] |
| Apparent magnitude (B) | 16.9[4] |
| Apparent magnitude (R) | 14.4[4] |
| Apparent magnitude (J) | 11.331[4] |
| Apparent magnitude (K) | 10.17[5] |
| Astrometry | |
| Proper motion (μ) | RA: −0.642±0.032[1] mas/yr Dec.: −2.1055±0.024[1] mas/yr |
| Parallax (π) | 0.4298±0.0288 mas[1] |
| Distance | 7,600 ± 500 ly (2,300 ± 200 pc) |
| Details | |
| Mass | 8.1+1.9 −1.2[6] M☉ |
| Radius | 0.44[6] R☉ |
| Luminosity | 110,000+53,000 −30,000[6] L☉ |
| Temperature | 160,000[3] K |
| Other designations | |
| 2MASS J17320330-3504323, SSTGLMC G353.2744-00.8460 | |
| Database references | |
| SIMBAD | data |
Discovery
WR 93b was discovered in 2003 during a study of emission line stars from the AAO/UKST Southern Galactic Plane Hα Survey. It was published as the fourth galactic WO class star in 1994.[7] This was too late to be included in the VIIth Wolf Rayet catalogue,[8] but it is listed in an annex published in 2006.[5]
It lies in the direction of the Galactic Center and is thought to be part of the Scutum-Crux spiral arm. It is highly reddened and interstellar extinction causes it to be 6.5 magnitudes fainter at visual wavelengths than it otherwise would be.[7]
Features
WR 93b, of spectral classification WO3, is one of the very few known oxygen-sequence Wolf-Rayet stars, just four in the Milky Way galaxy and six in external galaxies. Modelling the atmosphere gives a luminosity around 110,000 L☉, very low for a Wolf-Rayet star.[6] It is a very small dense star, with a radius less than half of the sun's but with a mass nearly 10 solar masses. Very strong stellar winds, with a terminal velocity of 5,000 kilometers per second are causing WR 93b to lose 10−5 M☉/year.[3] For comparison, the Sun loses (2-3) x 10−14 solar masses per year due to its solar wind, several hundred million times less than WR 93b.
Evolutionary status
WO Wolf-Rayet stars are the last evolutionary stage of the most massive stars before exploding as supernovae, possibly with a gamma-ray burst.[9] It is very likely that WR 93b is on its last stages of nuclear fusion, near or beyond the end of helium burning.[10] It has been calculated that WR 93b will explode as a supernova within 8,000 years.[3]