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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, from being so reddened by interstellar extinction, and its distance of over 23,000 light years. 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.

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.

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.

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 M_☉/year, much more than the Sun's (2-3) x 10 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_☉.

References

1. ^ 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. ^ 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. ^ 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.

v t e Constellation of Scutum
List of stars in Scutum Scutum in Chinese astronomy
Stars	Bayer α β γ δ ε ζ η Variable R S UY V373 V452 V479 Other BD-11 4672 CoRoT-16 CoRoT-17 IRC −10414 2MASS J18450079–1409036 PSR B1828−11 PSR B1829−10 PSR J1841−0500 WR 114 WR 119 WR 120 WR 121-16 Stephenson 2 DFK 1 RSGC1-F01 RSGC1-F02 IRAS 18357-0604 Stephenson 2 DFK 49
Exoplanets BD-11 4672 b c CoRoT-16b CoRoT-17b
Star clusters	NGC 6649 6712 Other Alicante 7 Alicante 8 Alicante 10 Mercer 3 Messier 26 RSGC1 RSGC3 Stephenson 2 Wild Duck Cluster
Nebulae IC 1295
Category

• Wolf–Rayet stars
• 2MASS objects
• Scutum (constellation)
• Variable stars
• TIC objects