RW Cygni is a semiregular variable star in the constellation Cygnus, about a degree east of 2nd magnitude γ Cygni. Its apparent magnitude varies between 8.05 and 9.70 and its spectral type between M3 and M4.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 20h 28m 50.59027s[1] |
| Declination | 39° 58′ 54.4180″[1] |
| Apparent magnitude (V) | 8.05 - 9.70[2] |
| Characteristics | |
| Evolutionary stage | Red supergiant |
| Spectral type | M3-4Ia-Iab[3] |
| Variable type | SRc[2] |
| Astrometry | |
| Radial velocity (Rv) | −18.39±0.52[1] km/s |
| Proper motion (μ) | RA: –3.255[1] mas/yr Dec.: –5.511[1] mas/yr |
| Parallax (π) | 0.4602 ± 0.0897 mas[1] |
| Distance | 1,620±40[4] pc |
| Absolute magnitude (MV) | –6.41[5] |
| Details | |
| Radius | 1103+251 −177[6] R☉ |
| Luminosity | 126,000[4] L☉ |
| Temperature | 3,600[7] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
Distance
editThe Gaia Data Release 2 parallax for RW Cyg is 0.4602±0.0897 mas or a distance of around 2.2 kpc.[1] RW Cygni is assumed to be a member of the Cygnus OB9 stellar association and therefore around 3,600 light-years from the Solar System.[5][8] Newer observations based on the parallaxes of neighbouring OB stars give RW Cygni a distance of 1.62 kpc.[4]
Properties
editRW Cygni is a luminous red supergiant with a bolometric luminosity more than 100,000 L☉.[9][5] Its spectral type is given in the General Catalogue of Variable Stars as M2-4Ia-Iab, covering the range of previously published values. It has been defined as a standard star for the MK spectral classification of M3-M4Ia-Iab.[3] In 2005, the effective temperature is directly calculated to be 3,600 K, giving a radius of 980 R☉.[5] An alternate calculation gives a higher temperature of 3,920 K and a correspondingly lower radius of 680 R☉.[9] A newer measurement based on its angular diameter (5.09 mas) and is Gaia Data Release 2 parallax give it a larger radius of 1,100 R☉,[6] which would make RW Cygni one of the largest known stars. Using the more conservative figure, if it was placed at the center of Solar System, it would be extend past the orbit of Mars and into the asteroid belt.
The initial mass of RW Cygni has been estimated from its position relative to theoretical stellar evolutionary tracks to be around 20 M☉.[9] Observations of its atmosphere suggest that it is losing mass at a rate of 3.2×10−6 M☉ per year.[11]
RW Cygni is classified as a semiregular variable star. It is given the subtype SRc, indicating that it is a cool supergiant.[2] Its brightness varies from extremes of magnitude +8.0 and +9.5 with a period of 580±80 d. No long secondary period has been detected.[12]
See also
editReferences
edit- ^ a b c d e f g Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b c Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
- ^ a b Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373. S2CID 123149047.
- ^ a b c Davies, Ben; Beasor, Emma R. (March 2020). "The 'red supergiant problem': the upper luminosity boundary of Type II supernova progenitors". MNRAS. 493 (1): 468–476. arXiv:2001.06020. Bibcode:2020MNRAS.493..468D. doi:10.1093/mnras/staa174. S2CID 210714093.
- ^ a b c d Levesque, Emily M.; Massey, Philip; Olsen, K. A. G.; Plez, Bertrand; Josselin, Eric; Maeder, Andre; Meynet, Georges (2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not As Cool As We Thought". The Astrophysical Journal. 628 (2): 973–985. arXiv:astro-ph/0504337. Bibcode:2005ApJ...628..973L. doi:10.1086/430901. S2CID 15109583.
- ^ a b Norris, Ryan (2021-03-01). An Interferometric Imaging Survey of Red Supergiant Stars. Bibcode:2021csss.confE.263N. doi:10.5281/zenodo.4567641.
- ^ Norris, Ryan P. (2019). Seeing Stars Like Never Before: A Long-term Interferometric Imaging Survey of Red Supergiants (PDF) (PhD). Georgia State University.
- ^ Famaey, B.; Jorissen, A.; Luri, X.; Mayor, M.; Udry, S.; Dejonghe, H.; Turon, C. (2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters". Astronomy and Astrophysics. 405: 165. arXiv:astro-ph/0409579. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272. S2CID 17804304.
- ^ a b c Josselin, E.; Plez, B. (2007). "Atmospheric dynamics and the mass loss process in red supergiant stars". Astronomy and Astrophysics. 469 (2): 671. arXiv:0705.0266. Bibcode:2007A&A...469..671J. doi:10.1051/0004-6361:20066353. S2CID 17789027.
- ^ "Hipparcos Tools Interactive Data Access". Hipparcos. ESA. Retrieved 8 December 2021.
- ^ Mauron, N.; Josselin, E. (2011). "The mass-loss rates of red supergiants and the de Jager prescription". Astronomy and Astrophysics. 526: A156. arXiv:1010.5369. Bibcode:2011A&A...526A.156M. doi:10.1051/0004-6361/201013993. S2CID 119276502.
- ^ Kiss, L. L.; Szabó, Gy. M.; Bedding, T. R. (2006). "Variability in red supergiant stars: Pulsations, long secondary periods and convection noise". Monthly Notices of the Royal Astronomical Society. 372 (4): 1721–1734. arXiv:astro-ph/0608438. Bibcode:2006MNRAS.372.1721K. doi:10.1111/j.1365-2966.2006.10973.x. S2CID 5203133.