WR 111

WR 111
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Sagittarius
Right ascension	18h 08m 28.46870s
Declination	−21° 15′ 11.1844″
Apparent magnitude (V)	+7.82
Characteristics
Evolutionary stage	Wolf-Rayet
Spectral type	WC5
U−B color index	−0.38
B−V color index	−0.28
Astrometry
Proper motion (μ)	RA: 0.293±0.129 mas/yr ; Dec.: −1.527±0.107 mas/yr
Parallax (π)	0.5826 ± 0.0759 mas
Distance	1,630+320; −230 pc
Absolute magnitude (MV)	−4.26
Details
Semi-empirical model
Mass	13.0 M☉
Radius	1.99 R☉
Luminosity	245,000 L☉
Temperature	89,000 K
Hydrodynamical model
Mass	13.63 M☉
Radius	0.905 R☉
Luminosity	282,000 L☉
Temperature	140,000 K
Age	4.2 Myr
Other designations
	WR 111, HD 165763, HIP 88856, BD−21°4864, Hen 3-1599, 2MASS J18082846-2115113
Database references
SIMBAD	data

WR 111 (HD 165763) is a Wolf-Rayet (WR) star in the constellation Sagittarius. It is magnitude 7.8 and lies about 5,150 light-years away. It is one of the brightest and most closely studied WR stars.

History

In 1880, Edward Pickering reported that BD−21°4864 had a spectrum similar to a nova, but it was apparently a non-variable star that had been near 8th magnitude since at least 1849.^[9] It was included in Campbell's 1894 paper The Wolf-Rayet stars.^[10]

In the Henry Draper Catalogue, BD−21°4864 was listed as entry 165763 with a spectral type of Oa. It was described in 1925 as a "Be star" due to its very strong emission lines,^[11] and in 1927 as a class-O star with unusually broad emission features.^[12] After the classification of WR stars onto either the nitrogen or carbon sequence, HD 165763 was designated as WC6 and its temperature estimated from the strength of Ov and Civ emission.^[13]

In 1968, the WR spectral classes were revised and HD 165763 was used as an example of class WC5. In this catalogue, considered as the fifth catalogue of Wolf Rayet stars, it was designated MR 84.^[14] In the sixth WR catalogue, the current naming convention was adopted and this star was numbered as WR 111.^[15]

Location

WR 111 is one of the 20 brightest Wolf Rayet stars in the sky.^[16] It lies in a rich Milky Way field near to V4381 Sagittarii and HD 165516, but not apparently a member of the associated cluster.^[17]

Properties

WR 111 is considered an archetypal WC5 star, having dominant emission lines of Civ, plus strong Ciii emission as well as Oiii, Oiv, and Ov, but not Ovi.^[6]

Non-hydrodynamical atmospheric models calculate a "surface" temperature of 89,000 K. The surface in this context is defined as the depth in the atmosphere at which the optical depth reaches 20. This differs from the convention used for many types of star, due to the optically dense stellar winds of WR stars. The corresponding radius is at 2.10 R_☉.^[6] A more detailed individual study of WR 111 using a hydrodynamical atmospheric model gives a temperature of 140,000 K and a radius of 0.905 R_☉.^[7] The apparently large difference is due largely to a difference in the depth within the atmosphere at which the radius is defined.^[6] The luminosity of WR 111 is similar in both models at 245,000 L_☉ - 282,000 L_☉, and the masses are found to be 13.0 M_☉ and 13.83 M_☉, respectively.^[7]^[6]

The stellar wind from WR 111 is ejecting 20 millionths of the Sun's mass every year at a speed of 2,398 km/s.^[6] The mechanism driving the intense stellar wind is found to be an opacity bump deep within the atmosphere caused by highly ionised iron. The winds are then accelerated to high velocity in the outer atmosphere by less highly ionised iron and by carbon and oxygen.^[7]

References

^ ^a ^b van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
^ ^a ^b ^c Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
^ ^a ^b Michaux, Yannick J. L.; Moffat, Anthony F. J.; Chené, André-Nicolas; St-Louis, Nicole (2014). "On the origin of variable structures in the winds of hot luminous stars". Monthly Notices of the Royal Astronomical Society. 440 (1): 2–9. arXiv:1312.2864. Bibcode:2014MNRAS.440....2M. doi:10.1093/mnras/stt2102. S2CID 118595336.
^ ^a ^b ^c 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.
^ 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. arXiv:1912.10125. Bibcode:2020MNRAS.493.1512R. doi:10.1093/mnras/stz3614. S2CID 209444955.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Sander, A.; Hamann, W.-R.; Todt, H. (2012). "The Galactic WC stars. Stellar parameters from spectral analyses indicate a new evolutionary sequence". Astronomy & Astrophysics. 540: A144. arXiv:1201.6354. Bibcode:2012A&A...540A.144S. doi:10.1051/0004-6361/201117830. S2CID 119182468.
^ ^a ^b ^c ^d ^e ^f ^g Gräfener, G.; Hamann, W.-R. (2005). "Hydrodynamic model atmospheres for WR stars. Self-consistent modeling of a WC star wind". Astronomy and Astrophysics. 432 (2): 633. arXiv:astro-ph/0410697. Bibcode:2005A&A...432..633G. doi:10.1051/0004-6361:20041732. S2CID 18972175.
^ Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (2011). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". Monthly Notices of the Royal Astronomical Society. 410 (1): 190–200. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. S2CID 118629873.
^ Pickering, Edward C. (1880). "Novel Celestial Object". Nature. 22 (569): 483. Bibcode:1880Natur..22..483P. doi:10.1038/022483c0. S2CID 4137312.
^ Campbell, W. W. (1894). "The Wolf-Rayet stars". Astronomy and Astro-Physics. 13: 448. Bibcode:1894AstAp..13..448C.
^ Merrill, P. W.; Humason, M. L.; Burwell, C. G. (1925). "Discovery and Observations of Stars of Class Be". Astrophysical Journal. 61: 389. Bibcode:1925ApJ....61..389M. doi:10.1086/142899.
^ Payne, Cecilia H. (1927). "Spectroscopic Energy Diagrams for Five Stars of Class O". Harvard College Observatory Bulletin. 844: 17. Bibcode:1927BHarO.844...17P.
^ Beals, C. S. (1940). "On the Physical Characteristics of the Wolf Rayet Stars and their Relation to Other Objects of Early Type (with Plates VIII, IX)". Journal of the Royal Astronomical Society of Canada. 34: 169. Bibcode:1940JRASC..34..169B.
^ Smith, Lindsey F. (1968). "A revised spectral classification system and a new catalogue for galactic Wolf-Rayet stars". Monthly Notices of the Royal Astronomical Society. 138: 109–121. Bibcode:1968MNRAS.138..109S. doi:10.1093/mnras/138.1.109.
^ Van Der Hucht, K. A.; Conti, P. S.; Lundstrom, I.; Stenholm, B. (1981). "The Sixth Catalogue of galactic Wolf-Rayet stars, their past and present". Space Science Reviews. 28 (3): 227. Bibcode:1981SSRv...28..227V. doi:10.1007/BF00173260. S2CID 121477300.
^ Van Der Hucht, Karel A. (2001). "The VIIth catalogue of galactic Wolf-Rayet stars". New Astronomy Reviews. 45 (3): 135–232. Bibcode:2001NewAR..45..135V. doi:10.1016/S1387-6473(00)00112-3.
^ Kharchenko, N. V.; Piskunov, A. E.; Schilbach, E.; Röser, S.; Scholz, R.-D. (2013). "Global survey of star clusters in the Milky Way. II. The catalogue of basic parameters". Astronomy & Astrophysics. 558: A53. arXiv:1308.5822. Bibcode:2013A&A...558A..53K. doi:10.1051/0004-6361/201322302. S2CID 118548517.