Astronomy:WR 128
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Sagitta[2] |
| Right ascension | 19h 48m 32.19674s[3] |
| Declination | +18° 12′ 03.6956″[3] |
| Apparent magnitude (V) | 10.51 |
| Characteristics | |
| Evolutionary stage | Wolf-Rayet |
| Spectral type | WN4(h)-w[4] |
| U−B color index | −0.89[5] |
| B−V color index | −0.02[5] |
| Astrometry | |
| Radial velocity (Rv) | 100.00[6] km/s |
| Proper motion (μ) | RA: −0.233[3] mas/yr Dec.: −5.455[3] mas/yr |
| Parallax (π) | 0.2836 ± 0.0202[3] mas |
| Distance | 2,900+540 −390[7] pc |
| Absolute magnitude (MV) | −3.27[4] |
| Details | |
| Mass | 11[4] M☉ |
| Radius | 2.69[4] R☉ |
| Luminosity | 166,000[4] L☉ |
| Temperature | 70,800[4] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
WR 128 is a Wolf–Rayet star located about 9,500 light years away in the constellation of Sagitta. A member of the WN class, WR 128's spectrum resembles that of a WN4 star, but hydrogen is clearly present in the star (hence the h in its spectrum), making it the only known hydrogen-rich WN4 star in the galaxy. However, similar H-rich very early WN stars can be found in the LMC and especially in the SMC, but the only other galactic examples of this are WR 3 and WR 152.[8]
In 1981, Igor Antokhin et al. discovered that the star, then known as HD 187282, is a variable star.[9] It was given its variable star designation, QT Sagittae, in 1985.[10]
Properties
Analysis of WR 128's spectrum with PoWR shows that it has a temperature of around 70,800 K and is losing mass at a very slow pace (in Wolf-Rayet terms), at 10−5.4 M☉/yr, or in other words, 1 solar mass every 250,000 years.[4] All this mass is being carried by a very strong stellar wind with a terminal velocity of 2,050 kilometres per second. Taking its distance into account, WR 128 has a luminosity of 166,000 L☉, or 105.22 L☉,[4] making it one of the dimmest galactic WN stars. Using the Stefan-Boltzmann Law, we can calculate a radius of 2.69 R☉. A "transformed" radius at an optical depth of 2/3, more comparable to other types of stars, is at about 13 R☉.[4]
References
- ↑ Antokhin, I. I.; Cherepashchuk, A. M. (January 1985). "Wolf-Rayet stars with possible relativistic companions - Light curves and orbital periods for the WN stars HD 187282, HD 192163". Soviet Astronomy Letters 11: 355–358. Bibcode: 1985SvAL...11..355A.
- ↑ 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 3.2 3.3 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.
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 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.
- ↑ 5.0 5.1 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.
- ↑ 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. doi:10.1002/asna.200710776. ISSN 0004-6337. Bibcode: 2007AN....328..889K.
- ↑ 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. doi:10.1093/mnras/stz3614. Bibcode: 2020MNRAS.493.1512R.
- ↑ Marchenko, S. V.; Moffat, A. F. J.; Crowther, P. A.; Chené, A.-N.; De Serres, M.; Eenens, P. R. J.; Hill, G. M.; Moran, J. et al. (2004-09-01). "Hydrogen in the atmosphere of the evolved WN3 Wolf-Rayet star WR 3: defying an evolutionary paradigm?". Monthly Notices of the Royal Astronomical Society 353 (1): 153–161. doi:10.1111/j.1365-2966.2004.08058.x. ISSN 0035-8711. Bibcode: 2004MNRAS.353..153M.
- ↑ Antokhin, I. I.; Aslanov, A. A.; Cherepashchuk, A. M. (December 1982). "HD 187282 - A possible Wolf-Rayet binary with a low-mass companion". Soviet Astronomy Letters 8: 395–398. Bibcode: 1982SvAL....8..395A.
- ↑ Kholopov, P. N.; Samus, N. N.; Kazarovets, E. V.; Perova, N. B. (March 1985). "The 67th Name-List of Variable Stars". Information Bulletin on Variable Stars 2681: 1–32. Bibcode: 1985IBVS.2681....1K. https://ibvs.konkoly.hu/pub/ibvs/2601/2681.pdf. Retrieved 26 October 2025.
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