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WR 120

A near-infrared (2.033 micron) light curve for V462 Scuti, adapted from Chené and St-Louis (2007). [1] The left-most point shows the 3 sigma error bar.
Observation data
Epoch J2000       Equinox J2000
Constellation Scutum
Right ascension 18h 41m 00.86698s [2]
Declination −4° 26′ 14.47345″ [2]
Apparent magnitude (V) 11.93 [3]
Characteristics
Evolutionary stage Wolf-Rayet
Spectral type WN7w [4] + WN3/4 [5]
U−B color index 0.13 [6]
B−V color index 1.04 [6]
Astrometry
Proper motion (μ) RA: −0.489 [7]  mas/ yr
Dec.: −2.524 [7]  mas/ yr
Parallax (π)0.3246 ± 0.0541  mas [7]
Distanceapprox. 10,000  ly
(approx. 3,100  pc)
Absolute magnitude (MV)−3.81 [4]
Details
Mass7 [4]  M☉
Radius3.78 [4]  R☉
Luminosity83,200 [4]  L☉
Temperature50,100 [4]  K
Other designations
MR 89, V462 Scuti, 2MASS J18410086-0426145
Database references
SIMBAD data

WR 120 is a binary containing two Wolf-Rayet stars in the constellation of Scutum, around 10,000 light years away. The primary is a hydrogen-free weak-lined WN7 star, the secondary is a hydrogen-free WN3 or 4 star, and the system is a possible member of the cluster Dolidze 33. [8] From our point of view, WR 120 is reddened by 4.82 magnitudes, and it has the variable designation of V462 Scuti. [9]

Properties

Analysis of the primary's spectrum with PoWR shows that it has a temperature of around 50,000 Kelvins, and is losing mass at a rate of 10−4.9 M☉/year, or 1 solar mass every 80,000 years, which is being carried away from the surface at a speed of 1,225 kilometres per second. [4] Taking its close distance into account, WR 120 A's luminosity turns out to be a mere 83,200  L☉, which would make it one of the dimmest WN stars known, and one of the only WN stars with a luminosity below 100,000  L☉. Using the Stefan-Boltzmann Law, a radius of 3.78 R☉ is derived, and a "transformed" radius at an optical depth of 2/3, more comparable to other types of stars, is at about 6 R☉. Using the WR Luminosity-Mass ratio, WR 120 may have a mass of just 7 M☉, one of the lowest masses of any WR star. WR 120 A’s visual luminosity is 2,858  L☉, which is also on the lower end of WR visual luminosities. [4]

WR 120 is thought to be a member of Dolidze 33, an open cluster nearly 3,000 pc away. [8]

Binarity

In 2021, WR 120 was revealed to be a binary star. Previously, it was thought to be a single WR star, but it is in fact a rare double Wolf-Rayet star. The companion (a WN3/4 WR star) is located approximately 1700 AU from the primary WN7 WR, and is about 2.1 magnitudes fainter than WR 120.

References

  1. ^ Chené, André-Nicolas (2007). "The First Determination of the Rotation Rates of Wolf-Rayet Stars". Massive Stars as Cosmic Engines, Proceedings IAU Symposium. 250: 139–144. doi: 10.1017/S1743921308020425.
  2. ^ a b Gaia Collaboration (2018-04-01). "VizieR Online Data Catalog: Gaia DR2 (Gaia Collaboration, 2018)". VizieR Online Data Catalog. 1345. Bibcode: 2018yCat.1345....0G.
  3. ^ Zacharias, N. (2012). "The fourth US Naval Observatory CCD Astrograph Catalog (UCAC4)". VizieR On-line Data Catalog. Bibcode: 2012yCat.1322....0Z.
  4. ^ a b c d e f g h Hamann, W.-R.; Gräfener, G.; Liermann, A.; Hainich, R.; Sander, A. A. C.; Shenar, T.; Ramachandran, V.; Todt, H.; Oskinova, L. M. (2019-05-01). "The Galactic WN stars revisited. Impact of Gaia distances on fundamental stellar parameters". Astronomy and Astrophysics. 625: A57. arXiv: 1904.04687. Bibcode: 2019A&A...625A..57H. doi: 10.1051/0004-6361/201834850. ISSN  0004-6361. S2CID  104292503.
  5. ^ Shara, Michael M.; Howell, Steve B.; Furlan, Elise; Gnilka, Crystal L.; Moffat, Anthony F. J.; Scott, Nicholas J.; Zurek, David (2022-01-01). "A speckle-imaging search for close and very faint companions to the nearest and brightest Wolf-Rayet stars". Monthly Notices of the Royal Astronomical Society. 509 (2): 2897–2907. arXiv: 2109.06975. Bibcode: 2022MNRAS.509.2897S. doi: 10.1093/mnras/stab2666. ISSN  0035-8711.
  6. ^ a b 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.
  7. ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv: 2012.01533. Bibcode: 2021A&A...649A...1G. doi: 10.1051/0004-6361/202039657. S2CID  227254300. (Erratum:  doi: 10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  8. ^ a b Rate, Gemma; Crowther, Paul A.; Parker, Richard J. (2020-06-01). "Unlocking Galactic Wolf-Rayet stars with Gaia DR2 - II. Cluster and association membership". Monthly Notices of the Royal Astronomical Society. 495 (1): 1209–1226. arXiv: 2005.02533. Bibcode: 2020MNRAS.495.1209R. doi: 10.1093/mnras/staa1290. ISSN  0035-8711.
  9. ^ 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.
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