The Keck Aperture‐masking Experiment: Near‐Infrared Sizes of Dusty Wolf‐Rayet Stars

We report the results of a high angular resolution near-infrared survey ofdusty Wolf-Rayet stars using the Keck-1 Telescope, including newmulti-wavelength images of the pinwheel nebulae WR 98a, WR 104, and WR 112.Angular sizes were measured for an additional 8 dusty WR stars using aperturemasking interferometry, allowing us to probe characteristics sizes down to ~20milliarcseconds (~40 AU for typical sources). With angular sizes and specificfluxes, we can directly measure the wavelength-dependent surface brightness andsize relations for our sample. We discovered tight correlations of theseproperties within our sample which could not be explained by simplespherically-symmetric dust shells or even the more realistic ``pinwheelnebula'' (3-D) radiative transfer model, when using optical constants of Zubko.While the tightly-correlated surface brightness relations we uncovered offercompelling indirect evidence of a shared and distinctive dust shell geometryamongst our sample, long-baseline interferometers should target themarginally-resolved objects in our sample in order to conclusively establishthe presence or absence of the putative underyling colliding wind binariesthought to produce the dust shells around WC Wolf-Rayets.Comment: Accepted by Astrophysical Journa