Sub-millimeter Imaging of Wolf-Rayet Binary Systems: Investigating Their Role in Dust Production

Low- and intermediate-mass stars in the Asymptotic Giant Branch (AGB) stage of evolution are the most dominant sources of dust in the Galaxy. The shocked colliding-wind region between Wolf-Rayet and OB binary systems also produce dust, as observed in near IR interferometric images. Although their dust contribution is much less than that of AGB stars, such systems could be important in explaining dusty galaxies at high red-shifts (z~6), e.g., SDSS J1148+5251, in which AGB evolution would be too slow to explain the amount of dust that is observed.

To characterize dust formation in Wolf-Rayet binaries, we have analyzed Submillimeter Array (SMA) archival data on a sample of five such “dustars”. We detected 870 micron continuum emission in three sources: WR112, WR140, and WR146 with flux densities 7.3±1.2, 26.3±2.4, 29.8±4.6 mJy respectively. These detections contribute to the currently sparse photometric data available for dustars at submillimeter wavelengths. WR98a and WR104 were non-detections with flux upper limits at 3-sigma of 6.9 and 12 mJy respectively. The continuum emission remains unresolved in our 1" synthesized beam, but WR140 shows hints of extended emission at 3-sigma level, and WR112 shows two point sources, both of which are displaced from the expected position of the WR star. CO J=3-2 emission is also detected and imaged in WR112. We present channel maps of CO emission in this source which shows an elongated structure associated with the central source.

We have compiled photometric data from the literature, at infrared and cm wavelengths, from VLA, 2MASS, WISE, and Spitzer observations, to construct spectral energy distribution (SED) plots for the three WR sources with SMA detections. We are currently modeling these model these SEDs in order to determine the dust contributions to the sub-mm flux, and thus estimate the cold dust masses.

The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. AST-1852268, and by the Smithsonian Institution.