Program: GN-2016B-Q-72

The existence of large amounts of circumstellar (CS) matter near non-supergiant hot stars is a longstanding puzzle of stellar astrophysics. We are investigating a recently defined group of FS CMa type objects, the largest group of dust-forming early-type stars. It includes ~50 objects and ~30 candidates ranging from 300 to 30,000 solar luminosities and exhibiting the B[e] phenomenon (forbidden lines and IR excess due to dust) with strong emission lines. This expands the range of hot dust-forming stars by two orders of magnitude toward lower luminosity. Physics of mass loss and dust formation in such objects is not understood, and accurate determination of temperature, luminosity, CS conditions, and evolutionary status is crucial for constraining stellar evolution. The current hypothesis is that FS CMa objects are binaries or result from the merger of a binary, and that those conditions explain the production of dust. This proposal concentrates on recently discovered or poorly characterized FS CMa objects for which we need to confirm the binarity. The high resolution spectra will be supplemented by lower-resolution spectra and multicolor optical photometry. The data will be modeled with a 3D radiation transfer code which calculates CS gaseous and dusty properties, and a Doppler tomography code which constraints the CS gas density distribution. The project's overall results will reveal the nature of the puzzling FS CMa group and test models of binary evolution.