WR 102

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WR 102
Observation data
J2000.0
Constellation Sagittarius
Right ascension 17h 45m 47.541s[1]
Declination −26° 10′ 27.78″[1]
Apparent magnitude (V) 14.10[2]
Characteristics
Evolutionary stage Wolf–Rayet star
Spectral type
WO2[3]
B−V color index +0.77[4]
Distance
9,500 ± 600 ly
(2,900 ± 200 pc)
Absolute magnitude (MV)−1.46[5]
Details
dex
V3893
 Sagittarii, LS 4368, ALS 4368, Sand 4
Database references
SIMBADdata
WR 102's size compared to the sun.

WR 102 is a Wolf–Rayet star in the constellation Sagittarius, an extremely rare star on the WO oxygen sequence. It is a luminous and very hot star, highly evolved and close to exploding as a supernova.

Discovery

WR 102 was first mentioned as the possible optical counterpart to a peculiar

variable star designation V3893 Sagittarii in the 62nd name-list of variable stars.[9]

Faint nebulosity was discovered around WR 102 in 1981 and was identified as a wind-blown bubble.[10] In 1982, a set of five luminous stars with highly ionised oxygen emission lines, including WR 102, was used to define the WO class of Wolf–Rayet stars. They were identified as highly evolved massive stars.[11]

Features

Infrared image of the nebulosity around WR 102 (WISE)

WR 102, of

spectral classification WO2, is one of the very few known oxygen-sequence Wolf–Rayet stars, just four in the Milky Way galaxy and nine in external galaxies. It is also one of the hottest known, with a surface temperature estimated to be at 210,000 K. Modelling the atmosphere gives a luminosity around 95,500 L☉,[5] while calculations from brightness and distance gives a luminosity of 380,000 L☉ (assuming a temperature of about 200,000 K) with a distance of 2,900±200 pc.[1][5] WR 102 was likely born from the OB association Sagittarius OB5.[12] It is a very small dense star, with a radius around 0.52 R☉ and a mass of 16.1 M☉.[5]

Very strong stellar winds with a terminal velocity of 5,000 kilometers per second are causing WR 102 to lose 10−5 M☉/year.[2] 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 102. These winds and the strong ultraviolet radiation from the hot star have compressed and ionised the surrounding interstellar material into a complex series of arcs described as the bubble type of Wolf–Rayet nebula.[13]

Evolutionary status

WO stars are the last evolutionary stage of the most massive stars before exploding as

helium burning.[15]

It has been calculated that WR 102 will explode as a supernova within 1,500 years.[3] High mass and rapid rotation would make a gamma-ray burst (GRB) possible,[14] but it is unclear if WR 102 is rotating rapidly.[3] It was previously thought that the projected rotation velocity within the stellar wind could be as fast as 1,000 km/s[2] but spectropolarimetric observations seem to indicate that if WR 102 is rotating, it is rotating at a much lower speed.[16]

See also

References

  1. ^
    S2CID 244398875
    . Gaia DR3 record for this source at VizieR.
  2. ^
    S2CID 119182468
    .
  3. ^
    S2CID 56093231
    .
  4. ISSN 0004-637X
    .
  5. ^
    S2CID 67754788
    .
  6. ^
    doi:10.1086/180694
    .
  7. Bibcode:1971PW&SO...1a...1S
    .
  8. Bibcode:1975A&A....39..307S
    .
  9. Bibcode:1977IBVS.1248....1K
    .
  10. doi:10.1086/159275
    .
  11. ISBN 978-90-277-1470-1
    .
  12. ISSN 0004-637X
    .
  13. S2CID 55776698
    .
  14. ^
    S2CID 84177572
    .
  15. S2CID 118870118
    .
  16. S2CID 119102624
    .
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