WR 3

WR 3
Observation data
Epoch J2000      Equinox J2000
Constellation Cassiopeia
Right ascension 01h 38m 55.62715s[1]
Declination +58° 09′ 22.67182″[1]
Apparent magnitude (V) 10.69[2]
Characteristics
Evolutionary stage Wolf-Rayet
Spectral type WN3-hw[3]
U−B color index −0.86[2]
B−V color index +0.02[2]
Astrometry
Radial velocity (Rv)100.00[4] km/s
Proper motion (μ) RA: −4.061±0.063[5] mas/yr
Dec.: −1.422±0.072[5] mas/yr
Parallax (π)0.3131 ± 0.0412 mas[5]
Distance2,900+520
−390[6] pc
Absolute magnitude (MV)−3.13[3]
Details
Mass15[3] M☉
Radius2.48[3] R☉
Luminosity363,000[3] L☉
Temperature89,100[3] K
Other designations
HD 9974, WR 3, HIP 7681, 2MASS J01385562+5809227
Database references
SIMBADdata

WR 3 is a Wolf-Rayet star located around 9,500 light years away from Earth in the constellation of Cassiopeia.

WR 3 is a member of the nitrogen sequence of WR stars and has a spectrum with strong HeII and NV lines, but weak NIV. HeI lines are very weak or missing, but there are lines of OVI. Unusually, there are lines of hydrogen and absorption components in many lines creating P Cygni profiles. The emission is weaker overall than stars of similar spectral type, and it has often been suggested that WR 3 has a type O binary companion. However, there are no other signs of a companion and it is thought to be a single star with a spectral type of WN3-hw. The "h" and "w" indicate that hydrogen is present and the emission is relatively weak for its class.[7][8]

Ordered by right ascension, WR 3 was the third star in the Sixth Catalogue of galactic Wolf-Rayet stars. WR 1 and WR 2 are also both early WN stars in Cassiopeiae.[9]

WR 3 is a massive and luminous star. The presence of hydrogen in its spectrum suggests that it is younger than hydrogen-free WR stars and may still be in the process of ejecting the remainder of its hydrogen. The emission lines of heavy elements in its spectrum are produced by strong convection and powerful stellar winds rather than complete loss of the outer layers of the star.[10] The wind has been measured at 2,700 km/s leading to mass being lost at four millionths M☉ per year.[3]

  1. ^ a b Cite error: The named reference hipparcos was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference ducati was invoked but never defined (see the help page).
  3. ^ a b c d e f g Cite error: The named reference hamann was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference ascc was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference dr2 was invoked but never defined (see the help page).
  6. ^ 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.
  7. ^ Cite error: The named reference smith was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference marchenko was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference VIth was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference smith2008 was invoked but never defined (see the help page).