WR 69

WR 69 is a Wolf–Rayet star located 11,350 light years away in the constellation of Triangulum Australe. It is classified as a WC9 star, belonging to the late-type carbon sequence. WR 69 is also a prolific dust maker, hence the "d" in its spectral type.[2]

WR 69
Observation data
Epoch J2000      Equinox J2000
Constellation Triangulum Australe
Right ascension 15h 24m 11.31117s[1]
Declination −62° 40′ 37.57531″[1]
Apparent magnitude (V) 9.1
Characteristics
Evolutionary stage Wolf-Rayet
Spectral type WC9d[2]
U−B color index 0.05[3]
B−V color index 0.414[3]
Astrometry
Radial velocity (Rv)0.00[4] km/s
Parallax (π)0.2559 ± 0.0343 mas[1]
Distance3,480+640
−470[5] pc
Absolute magnitude (MV)−5.51[2]
Details
Mass12.1[2] M☉
Radius9.77[2] R☉
Luminosity214,000[2] L☉
Temperature40,000[2] K
Other designations
HD 136488, WR 69, HIP 75377, 2MASS J15241131-6240374
Database references
SIMBADdata

Binarity

WR 69 is mostly considered as a binary (WC9d+O star), with a supposed period of 2.293 days and an amplitude of 0.044 magnitudes, suggesting it could be a short period Colliding-Wind Binary. However, this period is not in fact due to binary, but due to the fast rotation of the WC9d star, which rotates quickly, once every 2.15 days, and at 40% of its breakup velocity. The WC9d star is likely part of a much longer binary system, hence the absorption lines found in its spectrum.[6]

Properties

WR 69 is quite average for a WC9 star. Modelling WR 69's spectrum gives a temperature of 40,000 K, and a luminosity of ~214,000 L☉ is derived from Gaia DR2's parallax. From this a radius can be derived using the Stefan-Boltzmann Law, which turns out at just under 10 R☉.[2] However, in the visual wavelength, the star is just 13,600 L☉ bright,[2] because most of the 214,000 L☉ is emitted in the ultraviolet wavelength. WR 69 has 12.1 solar masses,[2] but it likely started its life with much more than this, and lost much of it through its powerful stellar wind.

WR 69 has a very strong stellar wind, typical of Wolf-Rayet stars. WR 69 loses 10-4.87 M☉ (about 1.35×10−5 M☉) per year because of this stellar wind, which has a terminal velocity of 1,089 kilometres per second.[2]

References
  1. Gaia Collaboration (2018-04-01). "VizieR Online Data Catalog: Gaia DR2 (Gaia Collaboration, 2018)". VizieR Online Data Catalog. 1345. Bibcode:2018yCat.1345....0G.
  2. Sander, A. A. C.; Hamann, W.-R.; Todt, H.; Hainich, R.; Shenar, T.; Ramachandran, V.; Oskinova, L. M. (2019-01-01). "The Galactic WC and WO stars. The impact of revised distances from Gaia DR2 and their role as massive black hole progenitors". Astronomy and Astrophysics. 621: A92. arXiv:1807.04293. Bibcode:2019A&A...621A..92S. doi:10.1051/0004-6361/201833712. ISSN 0004-6361. S2CID 67754788.
  3. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". VizieR Online Data Catalog. 2237. Bibcode:2002yCat.2237....0D.
  4. Kharchenko, N. V.; Scholz, R.-D.; Piskunov, A. E.; Röser, S.; Schilbach, E. (2007-11-01). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889–896. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. ISSN 0004-6337. S2CID 119323941.
  5. 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.
  6. Fahed, R.; Moffat, A. F. J. (2012-08-01). "Colliding winds in five WR+O systems of the Southern hemisphere". Monthly Notices of the Royal Astronomical Society. 424 (3): 1601–1613. Bibcode:2012MNRAS.424.1601F. doi:10.1111/j.1365-2966.2012.20494.x. ISSN 0035-8711.
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