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Using Adaptive Optics to probe the incidence of Binarity among Be Stars
  • Andrew MacGregor,
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Andrew MacGregor

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Abstract

A sample of 31 nearby Be stars within 100 pc have been observed with the Altair adaptive optics system at Gemini-North. Close companions were found in 4 cases. The sample was selected to include the nearest isolated Be stars in each spectral subtype. The proposed binaries have angular separations ranging from 0.13”-0.83”, corresponding to physical separations 19-78 AU. For the tightest binary, assuming low inclination and a circular orbit, the predicted orbital period is of order 20 years. JHK photometry indicates the companions are A-type stars. The incidence of companions in the range of magnitudes and separations found, is in excess of the random probability by a factor of ?? and in ? cases relative motion was measured. Binarity is a leading contender for explaining the origins and behavior of Be-stars, a unique and fascinating class that exhibit dynamic circumstellar disks and extreme rotation. Adaptive optics has opened a new parameter space for binary star searches not probed by radial velocity (RV) or light-curve studies.