WR 93b was discovered in 2003 during a study of emission line stars from the
AAO/
UKST Southern Galactic Plane
Hα 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 the
Galactic Center and is thought to be part of the
Scutum-Crux spiral arm. It is highly reddened and
interstellar extinction causes it to be 6.5 magnitudes fainter at visual wavelengths than it otherwise would be.[7]
Features
WR 93b, of
spectral classification WO3, is one of the very few known oxygen-sequence Wolf-Rayet stars, just four in the
Milky 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 of
the sun's but with a mass nearly 10 solar masses. Very strong
stellar winds, with a
terminal velocity of 5,000 kilometers per second are causing WR 93b to lose 10−5M☉/year.[3] For comparison, the Sun
loses (2-3) x 10−14 solar masses per year due to its
solar wind, several hundred million times less than WR 93b.
Evolutionary status
WO Wolf-Rayet stars are the last evolutionary stage of the most massive stars before exploding as
supernovae, possibly with a
gamma-ray burst.[9] It is very likely that WR 93b is on its last stages of
nuclear fusion, near or beyond the end of
helium 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.