Abstract
Some stars hotter than 10,000 K show propensity for unusual surface abundances and excessive magnetic fields. These peculiar stars, Ap and Bp in the spectral nomenclature, show unusually prominent absorption lines of heavier elements. Rapid rotation and strong magnetic fields are revealed by line shapes and Zeeman splitting. We have used very-long-baseline interferometry (VLBI) to directly probe the source size and brightness temperature of weak radio emission recently discovered from two isolated Bp stars, σ Orionis E and HD37017. The emitting zone for each star is no more than 6 stellar diameters in extent, reflecting brightness temperatures of more than 109 K. Such high surface brightness resembles gyrosynchrotron radiation from mildly relativistic electrons trapped in the strong magnetic fields surrounding these stars1,2. Compact radio radiation from these two stars presents new opportunities for probing the physical environments of early-type stars and for precise radio astrometry.
Published Version
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