WR 93b was discovered in 2003 during a study of emission line stars from theAAO/UKST Southern Galactic PlaneHα Survey. It was published as the fourth galactic WO class star in 1994.[7] This was too late to be included in the VIIth Wolf Rayet catalogue,[8] but it is listed in an annex published in 2006.[5]
It lies in the direction of theGalactic Center and is thought to be part of theScutum-Crux spiral arm. It is highly reddened andinterstellar extinction causes it to be 6.5 magnitudes fainter at visual wavelengths than it otherwise would be.[7]
WR 93b, ofspectral classification WO3, is one of the very few known oxygen-sequence Wolf-Rayet stars, just four in theMilky Waygalaxy and six in external galaxies. Modelling the atmosphere gives a luminosity around 110,000 L☉, very low for a Wolf-Rayet star.[6] It is a very small dense star, with a radius less than half ofthe sun's but with a mass nearly 10 solar masses. Very strongstellar winds, with aterminal velocity of 5,000 kilometers per second are causing WR 93b to lose 10−5M☉/year.[3] For comparison, the Sunloses (2-3) x 10−14 solar masses per year due to itssolar wind, several hundred million times less than WR 93b.
WO Wolf-Rayet stars are the last evolutionary stage of the most massive stars before exploding assupernovae, possibly with agamma-ray burst.[9] It is very likely that WR 93b is on its last stages ofnuclear fusion, near or beyond the end ofhelium burning.[10] It has been calculated that WR 93b will explode as a supernova within 8,000 years.[3]
^Henden, Arne A.; Levine, Stephen; Terrell, Dirk; Welch, Douglas L. (2015). "APASS - the Latest Data Release".American Astronomical Society Meeting Abstracts #225.225: 336.16.Bibcode:2015AAS...22533616H.
^abcCutri, 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.
