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WR 31a is a Wolf-Rayet star in the southern constellation of Carina that is surrounded by an expanding nebula. It is more commonly referred to as Hen 3-519, as it was known before being listed in the Catalogue of Wolf Rayet stars. It is a suspected, dormant, or post-Luminous Blue Variable (LBV).
Properties
The spectrum of Hen 3-519 contains both absorption and emission lines, intermediate between a hot supergiant and a Wolf-Rayet. On this basis it has been classified as Ofpe/WN9, a slash star. The same type of spectrum is also known as WN11, an extension of the traditional nitrogen sequence to cooler temperatures. It is a hydrogen-rich star, a young object rather than a highly evolved dying star.
Luminous Blue Variable
Hen 3-519 has been considered as a possible LBV almost since the term was first coined, although it has never shown the characteristic LBV variability. Its properties place it at the limit of temperature and luminosity for such stars, although comparable to the confirmed LBV AG Carinae.
Wolf-Rayet Nebula
The nebula around WR 31a was first catalogued by Ellen Dorrit Hoffleit in 1953 as the planetary nebulaHf 39. Since 2013, the object has been considered not a planetary nebula but rather, an expanding shocked gas shell, formally classified as a Wolf–Rayet nebula or WR nebula. Its observed expansion velocity is 365 km.s, estimated to be some 2.4 parsecs across.
References
^ Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H.
Smith, Nathan; Tombleson, Ryan (2015). "Luminous blue variables are antisocial: Their isolation implies that they are kicked mass gainers in binary evolution". Monthly Notices of the Royal Astronomical Society. 447: 598. arXiv:1406.7431. Bibcode:2015MNRAS.447..598S. doi:10.1093/mnras/stu2430.{{cite journal}}: CS1 maint: unflagged free DOI (link)
Davidson, Kris; Humphreys, Roberta M.; Hajian, Arsen; Terzian, Yervant (1993). "He 3-519 - A peculiar post-LBV, pre-WN star?". Astrophysical Journal. 411: 336. Bibcode:1993ApJ...411..336D. doi:10.1086/172833.
Frew, D. J.; Bojicic, I. S.; Parker, Q. A. (2013). "A catalogue of integrated Hα fluxes for 1258 Galactic planetary nebulae". Monthly Notices of the Royal Astronomical Society. 431: 2. Bibcode:2013MNRAS.431....2F. doi:10.1093/mnras/sts393.{{cite journal}}: CS1 maint: unflagged free DOI (link)
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