WR 148 shows a classic WN8h spectrum, but with the addition of weak central absorption on some of the
emission lines.[11] NIII and NIV emission lines are stronger than NV, and HeI lines are stronger than HeII, The
Balmer series hydrogen lines and some other lines have
P Cygni profiles.[12]
WR 148 is erratically variable on timescales ranging from seconds to years, but it shows consistent brightness and
radial velocity variations with a period of 4.32 days. There is little doubt that it is a binary system, due to the regular variations and the presence of hard x-ray radiation from colliding winds, but the secondary is not clearly detectable in the spectrum.[4] One proposal for a companion that would match the faint absorption features would be a B3
subgiant, but that is not compatible with the orbit. An early calculated orbit based on faint absorption features gave a relatively large mass ratio which imply either a very high companion mass, meaning a black hole, or an unreasonably low primary mass for a luminous WR star.[11] Another analysis of the spectrum finds absorption features consistent with an O5 star, similar masses for the two components, and only a small orbital inclination.[4]
Because of its erratic changes in
apparent magnitude at so many frequencies WR 148 is classified in the
General Catalogue of Variable Stars as a unique type of variable, not a member of any of the defined classes.[3] The shape of the light curve is unusual and has been modelled as being produced by an extended secondary object which may be an ionised cavity in the dense wind of the primary star, produced as the secondary orbits at a distance comparable to the radius of the primary star.[11]
WR 148 is found unusually far from the
galactic plane for a Wolf–Rayet star, at 500–800
pc. Young massive stars such as WN8h WR stars are members of the thin disc population, on average only 60 pc from the galactic plane. It is suggested that WR 148 is a runaway from a
supernova explosion.[11] Calculations based on its large
peculiar velocity of 197
km/s, current binary orbit, and likely lifetime since any supernova, are consistent with expulsion from a very massive triple system.[4]
References
^"OMC Archive". OMC Archive. The Astronomical Data Centre at CAB. Retrieved 19 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.
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2009yCat....102025S.
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abcdefghiMunoz, Melissa; Moffat, Anthony F. J.; Hill, Grant M.; Shenar, Tomer; Richardson, Noel D.; Pablo, Herbert; St-Louis, Nicole; Ramiaramanantsoa, Tahina (2017). "WR 148: Identifying the companion of an extreme runaway massive binary*". Monthly Notices of the Royal Astronomical Society. 467 (3): 3105.
arXiv:1609.08289.
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2017MNRAS.467.3105M.
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^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.
^
abDucati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237.
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^Sota, A.; Maíz Apellániz, J.; Morrell, N. I.; Barbá, R. H.; Walborn, N. R.; Gamen, R. C.; Arias, J. I.; Alfaro, E. J.; Oskinova, L. M. (2019). "The Galactic WN stars revisited. Impact of Gaia distances on fundamental stellar parameters". Astronomy & Astrophysics. A57: 625.
arXiv:1904.04687.
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