WR 120

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WR 120
V462SctLightCurve.png
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]
Distance approx. 10,000  ly
(approx. 3,100  pc)
Absolute magnitude  (MV)−3.81 [4]
Details
Mass 7 [4]   M☉
Radius 3.78 [4]   R☉
Luminosity 83,200 [4]   L☉
Temperature 50,100 [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.

Contents

Photometric observations obtained in 1995 by Sergey V. Marchenko et al. showed that WR 120 is a variable star. [9] For that reason it was given its variable star designation, V462 Scuti, in the year 2000. [10]

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. 1 2 Gaia Collaboration (2018-04-01). "VizieR Online Data Catalog: Gaia DR2 (Gaia Collaboration, 2018)". VizieR Online Data Catalog. 1345. Bibcode:2018yCat.1345....0G. doi:10.26093/cds/vizier.1345.
  3. ↑ Zacharias, N. (2012). "The fourth US Naval Observatory CCD Astrograph Catalog (UCAC4)". VizieR On-line Data Catalog. Bibcode:2012yCat.1322....0Z.
  4. 1 2 3 4 5 6 7 8 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. 1 2 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. 1 2 3 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. 1 2 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. ↑ Marchenko, S. V.; Moffat, A. F. J.; Eversberg, T.; Morel, T.; Hill, G. M.; Tovmassian, G. H.; Seggewiss, W. (March 1998). "A comprehensive variability study of the enigmatic WN8 stars: final results". Monthly Notices of the Royal Astronomical Society. 294: 642–656. Bibcode:1998MNRAS.294..642M. doi:10.1111/j.1365-8711.1998.01174.x . Retrieved 14 September 2025.
  10. ↑ Kazarovets, E. V.; Samus, N. N.; Durlevich, O. V. (March 2000). "The 75th Name-List of Variable Stars" (PDF). Information Bulletin on Variable Stars. 4870: 1–47. Bibcode:2000IBVS.4870....1K . Retrieved 14 September 2025.
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