Astronomy:WR 120
250px 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 Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Scutum[2] |
| Right ascension | 18h 41m 00.86698s[3] |
| Declination | −4° 26′ 14.47345″[3] |
| Apparent magnitude (V) | 11.93[4] |
| Characteristics | |
| Evolutionary stage | Wolf-Rayet[5] |
| Spectral type | WN7w[6] + WN3/4[5] |
| U−B color index | 0.13[7] |
| B−V color index | 1.04[7] |
| Astrometry | |
| Proper motion (μ) | RA: −0.489[8] mas/yr Dec.: −2.524[8] mas/yr |
| Parallax (π) | 0.3246 ± 0.0541[8] mas |
| Distance | approx. 10,000 ly (approx. 3,100 pc) |
| Absolute magnitude (MV) | −3.81[6] |
| Details | |
| Mass | 7[6] M☉ |
| Radius | 3.78[6] R☉ |
| Luminosity | 83,200[6] L☉ |
| Temperature | 50,100[6] K |
| Other designations | |
| 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.[9] From our point of view, WR 120 is reddened by 4.82 magnitudes.
Photometric observations obtained in 1995 by Sergey V. Marchenko et al. showed that WR 120 is a variable star.[10] For that reason it was given its variable star designation, V462 Scuti, in the year 2000.[11]
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.[6] 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.[6]
WR 120 is thought to be a member of Dolidze 33, an open cluster nearly 3,000 pc away.[9]
Binarity
In 2021, WR 120 was revealed to have a close companion. Previously, it was thought to be a single WR star. The companion is thought to be a WN3/4 WR star and would be located at least 1,700 AU from the primary WN7 WRl it is about two magnitudes fainter than WR 120.[5]
References
- ↑ 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.
- ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific 99 (617): 695. doi:10.1086/132034. Bibcode: 1987PASP...99..695R Constellation record for this object at VizieR.
- ↑ 3.0 3.1 Gaia Collaboration (2018-04-01). "VizieR Online Data Catalog: Gaia DR2 (Gaia Collaboration, 2018)". VizieR Online Data Catalog 1345. doi:10.26093/cds/vizier.1345. Bibcode: 2018yCat.1345....0G.
- ↑ Zacharias, N. (2012). "The fourth US Naval Observatory CCD Astrograph Catalog (UCAC4)". VizieR On-line Data Catalog. Bibcode: 2012yCat.1322....0Z.
- ↑ 5.0 5.1 5.2 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. doi:10.1093/mnras/stab2666. ISSN 0035-8711. Bibcode: 2022MNRAS.509.2897S.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 Hamann, W.-R.; Gräfener, G.; Liermann, A.; Hainich, R.; Sander, A. A. C.; Shenar, T.; Ramachandran, V.; Todt, H. et al. (2019-05-01). "The Galactic WN stars revisited. Impact of Gaia distances on fundamental stellar parameters". Astronomy and Astrophysics 625: A57. doi:10.1051/0004-6361/201834850. ISSN 0004-6361. Bibcode: 2019A&A...625A..57H.
- ↑ 7.0 7.1 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.
- ↑ 8.0 8.1 8.2 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 9.0 9.1 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. doi:10.1093/mnras/staa1290. ISSN 0035-8711. Bibcode: 2020MNRAS.495.1209R.
- ↑ 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 (4): 642–656. doi:10.1111/j.1365-8711.1998.01174.x. Bibcode: 1998MNRAS.294..642M.
- ↑ Kazarovets, E. V.; Samus, N. N.; Durlevich, O. V. (March 2000). "The 75th Name-List of Variable Stars". Information Bulletin on Variable Stars 4870: 1–47. Bibcode: 2000IBVS.4870....1K. https://ibvs.konkoly.hu/pub/ibvs/4801/4870.pdf. Retrieved 14 September 2025.
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