Astronomy:WR 21a
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Carina |
| Right ascension | 10h 25m 56.502s[1] |
| Declination | −57° 48′ 43.52″[1] |
| Characteristics | |
| Spectral type | O3/WN5ha + O3Vz((f*))[2] |
| B−V color index | +1.507[3] |
| Variable type | Eclipsing[4] |
| Astrometry | |
| Proper motion (μ) | RA: −4.079[1] mas/yr Dec.: 2.617[1] mas/yr |
| Parallax (π) | 0.2497 ± 0.0143[1] mas |
| Distance | 13,100 ± 700 ly (4,000 ± 200 pc) |
| Absolute magnitude (MV) | −7.20[2] |
| Orbit[4] | |
| Primary | WR |
| Companion | O |
| Period (P) | 31.67855±0.00002 days |
| Semi-major axis (a) | 230 R☉[5] |
| Eccentricity (e) | 0.695±0.007 |
| Inclination (i) | 61.8±1.5° |
| Semi-amplitude (K1) (primary) | 158.0±2.7 km/s |
| Semi-amplitude (K2) (secondary) | 278.1±2.8 km/s |
| Details | |
| WR | |
| Mass | 94.4[4] M☉ |
| Radius | 23.3±1.6[4] R☉ |
| Luminosity | 1,510,000[4] L☉ |
| Surface gravity (log g) | 3.69[4] cgs |
| Temperature | 45,000[6] K |
| O | |
| Mass | 53.6[4] M☉ |
| Radius | 14.8±2.0[4] R☉ |
| Luminosity | 1,050,000[4] L☉ |
| Surface gravity (log g) | 3.81[4] cgs |
| Temperature | 50,680[6] K |
| Age | 1.5[2] Myr |
| Other designations | |
WR 21a, 2MASS J10255650-5748435 | |
| Database references | |
| SIMBAD | data |
WR 21a is an eclipsing binary star in the constellation Carina. It includes one of the most massive known stars and is one of the most massive binaries.
WR 21a lies near the Westerlund 2 open cluster[7] and likely to be an ejected member.[8]
The distance of WR 21a was not definitively known until Gaia mission. There have been estimates from 2.85 kpc to around 8 kpc, with consequent uncertainties in the system luminosity. The larger distance was preferred because of consistency with the derived orbital parameters.[6][9]
Every 31 days and 16 hours the two stars in this system revolve around each other. The inclination of the orbit means that only very shallow eclipses are observed and the brightness dips by only about 0.05 magnitudes. There are also even smaller brightness variations attributed to the heartbeat effect where the closest passage of the stars in their eccentric orbits creates brightness changes as the two stars illuminate each other. There may also be tidally-excited oscillations producing further small variations.[4]
The colliding winds of the two stars produce extremely high temperatures and luminous x-ray emission.[5] The system is also bright at radio wavelengths.[6]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 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.
- ↑ 2.0 2.1 2.2 Tramper, F.; Sana, H.; Fitzsimons, N. E.; De Koter, A.; Kaper, L.; Mahy, L.; Moffat, A. (2016). "The mass of the very massive binary WR21a". Monthly Notices of the Royal Astronomical Society 455 (2): 1275–1281. doi:10.1093/mnras/stv2373. Bibcode: 2016MNRAS.455.1275T.
- ↑ Cite error: Invalid
<ref>tag; no text was provided for refs nameducac4 - ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 Barbá, Rodolfo H.; Gamen, Roberto C.; Martín-Ravelo, Pablo; Arias, Julia I.; Morrell, Nidia I. (2022). "The winking eye of a very massive star: WR 21a revealed as an eclipsing binary by TESS". Monthly Notices of the Royal Astronomical Society 516 (1): 1149. doi:10.1093/mnras/stac2173. Bibcode: 2022MNRAS.516.1149B.
- ↑ 5.0 5.1 Gosset, Eric; Naze, Yael (2016). "The X-ray light curve of the massive colliding wind Wolf-Rayet + O binary WR21a". Astronomy & Astrophysics 1604: A113. doi:10.1051/0004-6361/201527051. Bibcode: 2016A&A...590A.113G.
- ↑ 6.0 6.1 6.2 6.3 Benaglia, P.; Romero, G. E.; Koribalski, B.; Pollock, A. M. T. (2005). "Multiwavelength studies of WR 21a and its surroundings". Astronomy and Astrophysics 440 (2): 743–750. doi:10.1051/0004-6361:20042617. Bibcode: 2005A&A...440..743B.
- ↑ Hur, Hyeonoh; Park, Byeong-Gon; Sung, Hwankyung; Bessell, Michael S.; Lim, Beomdu; Chun, Moo-Young; Sohn, Sangmo Tony (2015). "Reddening, distance, and stellar content of the young open cluster Westerlund 2". Monthly Notices of the Royal Astronomical Society 446 (4): 3797–3819. doi:10.1093/mnras/stu2329. Bibcode: 2015MNRAS.446.3797H.
- ↑ Maíz Apellániz, J.; Crespo Bellido, P.; Barbá, R. H.; Fernández Aranda, R.; Sota, A. (2020), "The Villafranca catalog of Galactic OB groups", Astronomy & Astrophysics 643: A138, doi:10.1051/0004-6361/202038228
- ↑ Carraro, G.; Turner, D.; Majaess, D.; Baume, G. (2013). "The distance to the young open cluster Westerlund 2". Astronomy & Astrophysics 555: A50. doi:10.1051/0004-6361/201321421. Bibcode: 2013A&A...555A..50C.
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