WR 133 is one of the brightest Wolf Rayet (WR) stars in the northern hemisphere, slightly brighter than WR 140 which also in Cygnus.[8] The WR star is typically identified as the primary, being more luminous, and dominating the spectrum. However, the supergiant secondary is more massive and visually brighter. The primary star is a WN5 nitrogen-rich WR star and the secondary has a spectral type of O9I. The orbit is moderately eccentric and has a period of 113 d, which has been determined from the velocity variations observed with the component's spectral lines, mostly from the HeIIemission lines at 541.1 nm for the WR primary, and helium and oxygen absorption lines for the primary. This is the first WN-type WR star to have its mass dynamically determined from orbital motion, although the precision is hampered by the nearly face-on orientation of the orbit.[4]
^Marchenko, S. V.; Moffat, A. F. J.; van der Hucht, K. A.; Seggewiss, W.; Schrijver, H.; Stenholm, B.; Lundström, I.; Setia Gunawan, D. Y. A.; Sutantyo, W.; van den Heuvel, E. P. J.; De Cuyper, J. P.; Gómez, A. E. (March 1998). "Wolf-Rayet stars and O-star runaways with HIPPARCOS II. Photometry". Astronomy and Astrophysics. 331: 1022–1036. Bibcode:1998A&A...331.1022M. Retrieved 28 December 2021.
^ abcSamus, 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.
^ abCutri, 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.
^ abDucati, J. R. (2002). "VizieR On-line Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
^Fahed, R.; Moffat, A. F. J.; Zorec, J.; Eversberg, T.; Chené, A. N.; Alves, F.; Arnold, W.; Bergmann, T.; Corcoran, M. F.; Correia Viegas, N. G.; Dougherty, S. M.; Fernando, A.; Frémat, Y.; Gouveia Carreira, L. F.; Hunger, T.; Knapen, J. H.; Leadbeater, R.; Marques Dias, F.; Martayan, C.; Morel, T.; Pittard, J. M.; Pollock, A. M. T.; Rauw, G.; Reinecke, N.; Ribeiro, J.; Romeo, N.; Sánchez-Gallego, J. R.; Dos Santos, E. M.; Schanne, L.; et al. (2011). "Spectroscopy of the archetype colliding-wind binary WR 140 during the 2009 January periastron passage". Monthly Notices of the Royal Astronomical Society. 418 (1): 2–13. Bibcode:2011MNRAS.418....2F. doi:10.1111/j.1365-2966.2011.19035.x.