0 Assigned ID: 4401 ----- Attempting Submission 1 (Wed May 24 16:34:07 GMT 2023) ----- Understanding massive star evolution is important for a variety of astrophysical processes, from the formation of the elements to the generation of gravitational waves as their remnants merge. Wolf-Rayet (WR) stars are evolved stars, where the hydrogen has been removed from a massive OB star, and its nuclear burning products revealed at the surface. This stripping can occur either by stellar winds or by interactions in close binaries. Although we expect the latter to be an important mechanism, there are few examples where one can argue which mechanism has been responsible, as single WRs may have formed through binary interaction, but merged with its companion. Given the large number of massive stars in binaries, we expect stripped remnants to be common. Binary models suggest these should look like WRs, but they are curiously absent where we expect to find them. However, the recent discovery of a WR binary in the LMC matches many of the properties expected for a stripped binary WR. We have obtained extensive ground-based photometry and spectroscopy of this object, and have carried the analysis as far as it is possible. The WR component is of WN4-type, but with intrinsic hydrogen and helium absorption lines. The companion is an "impossible" star, with a sub-solar mass and radius but a very high temperature. We suggest that this is the result of an Algol-like system, with both components having been donors and recipients at some point. This could be the archetype of binary-produced WRs. ULLYSES obtained UV spectra of this star, and analysis of these data will allow us to determine CNO abundances, stellar wind properties, and other physical properties of this unique star. Phil Massey is an astronomer at Lowell; he has been studying Wolf-Rayet stars since his graduate school days in the late 1970s. Kathryn Neugent is a Hubble Fellow at the CfA, and has been studying massive stars for the past 12 years. Laura Penny is a faculty member at the College of Charleston, and is an expert in the fitting of light-curves and the analysis of massive binaries. John Hillier is a professor at the Univeristy of Pittsburgh, and an expert in Wolf-Rayet model atmospheres; he wrote the modeling program CMFGEN. Nidia Morrell is a staff astronomer at Las Campanas, and in also an expert in massive stars. Neugent, Massey, and Morrell discovered LMCe055-1 as well as the other 9 WN3/O3 stars. Neugent took the lead in modeling the other 9 WN3/O3 stars; all have experience in reducing and modeling STIS and COS spectra. Stellar Physics and Stellar Types 0 Regular false false true false false false SUPPORTED