WR 121-16
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Scutum
Right ascension 18h 51m 39.7102s[1]
Declination −05° 34′ 51.066″[1]
Apparent magnitude (V) 14.02 (13.95 - 14.14)[2]
Characteristics
Spectral type WN7o/WC[2]
Apparent magnitude (J) 11.369[3]
Apparent magnitude (K) 10.609[3]
Astrometry
Proper motion (μ) RA: −2.450[1] mas/yr
Dec.: −6.943[1] mas/yr
Parallax (π)0.0776 ± 0.0156 mas[1]
Distance23,190[2] ly
(7,110 pc)
Absolute magnitude (MV)−3.955[2]
Details[2]
Mass7.1+1.7
−1.1 M☉
Radius4.14+1.4
−1.3 R☉
Luminosity75,900+36,300
−22,200 L☉
Temperature47,000+9,000
−5,000 K
Other designations
2MASS J18513970-0534510
Database references
SIMBADdata

WR 121-16 is a transitional Wolf-Rayet star in the constellation of Scutum, near the Wild Duck Cluster (M11). It is located in the Far 3 kpc Arm of the Milky Way. It is very dim from Earth, having an apparent magnitude of about 14,[2] from being so reddened by interstellar extinction, and its distance of over 23,000 light years.[4] It is one of the dimmest known conventional Wolf-Rayet stars, with a luminosity of less than 76,000 times that of the Sun. WR 121-16 varies irregularly between magnitudes 13.95 and 14.14.[2]

WR 121-16 is a recent addition to the Wolf-Rayet Star Catalogue, being the 667th star added. It was discovered in August 2020.

Discovery

WR 121-16 was originally discovered as a ‘by-product’ of the LAMOST testing observations during the full moon nights, when the telescope was pointing to the open cluster M11, with WR 121-16 being about 42′ 24 apart from the centre of M11.[2]

Features

WR 121-16 is one of a few transitional Wolf-Rayet stars, which display both carbon and nitrogen emission, with a spectral type of WN7o/WC. Modelling the spectrum shows that WR 121-16 is not very luminous at all, with a luminosity of just 75,900 L☉, much less than most Wolf-Rayet stars. WR 121-16 has just over 7 solar masses, nearly all of which is helium. 1.5% of the star is composed of nitrogen, and 0.2% of it is composed of carbon.[2]

Strong stellar winds, typical of Wolf-Rayet stars, with a terminal velocity of 1,000 kilometers per second are causing WR 121-16 to lose 10−4.97 M☉/year,[2] much more than the Sun's (2-3) x 10−14 solar masses per year. The winds are so dense that the photosphere of the star is not visible. Its radius is defined for consistency with other Wolf-Rayet stars as being at an optical depth of 20, at about 4 R☉. A "transformed" radius at an optical depth of 2/3, more comparable to other types of star, is at about 6 R☉.[2]

References

  1. 1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  2. 1 2 3 4 5 6 7 8 9 10 11 Zhang, Wei; Todt, Helge; Wu, Hong; Shi, Jianrong; Hsia, Chih-Hao; Wu, Yuzhong; Wu, Chaojian; Zhao, Yongheng; Zhang, Tianmeng; Hou, Yonghui (2020-10-12). "A New Transition Wolf-Rayet WN/C Star in the Milky Way". The Astrophysical Journal. 902 (1): 62. arXiv:2008.08205. Bibcode:2020ApJ...902...62Z. doi:10.3847/1538-4357/abb0e7. ISSN 1538-4357. S2CID 221172973.
  3. 1 2 Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
  4. ↑ "Wolf-Rayet Star Catalogue". pacrowther.staff.shef.ac.uk. Retrieved 2021-03-24.
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