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NaSt1 (aka Wolf-Rayet 122) is a peculiar emission-line star embedded in anextended nebula of [N II] emission with a compact dusty core. This object wascharacterized by Crowther & Smith (1999) as a Wolf-Rayet (WR) star cloaked inan opaque nebula of CNO-processed material, perhaps analogous to Eta Car andits Homunculus nebula, albeit with a hotter central source. To discern themorphology of the [N II] nebula we performed narrowband imaging using theHubble Space Telescope and Wide-field Camera 3. The images reveal that thenebula has a disk-like geometry tilted 12 degrees from edge-on, composed of abright central ellipsoid surrounded by a larger clumpy ring. Ground-basedspectroscopy reveals radial velocity structure (~10 km/s) near the outerportions of the nebula's major axis, which is likely to be the imprint ofoutflowing gas. Near-infrared adaptive-optics imaging with Magellan AO hasresolved a compact ellipsoid of Ks-band emission aligned with the larger [N II]nebula, which we suspect is the result of scattered He I line emission (2.06um). Observations with the Chandra X-ray Observatory have revealed an X-raypoint source at the core of the nebula that is heavily absorbed at energies <1keV and has properties consistent with WR stars and colliding-wind binaries. Wesuggest that NaSt1 is a WR binary embedded in an equatorial outflow that formedas the result of non-conservative mass transfer. NaSt1 thus appears to be arare and important example of a stripped-envelope WR forming through binaryinteraction, caught in the brief Roche-lobe overflow phase.

Multiwavelength Observations of NaSt1 (WR 122): Equatorial Mass Loss and X-rays from an Interacting Wolf-Rayet Binary