Very long baseline interferometry of chromospherically active binary stars

Some of the most surprising stellar behavior comes from the stars like our own Sun. These intermediate mass stars can have strong magnetic dynamos, a kind of overgrown cousin to the dynamo that gives the Earth its magnetic field, if they have a rapidly rotating and deep upper atmosphere. The magnetic dynamo powers phenomena that influence space weather, effecting satellites and potentially surface electrical infrastructure during extreme outbursts.

Rapidly rotating binary star systems composed of intermediate mass stars in very close orbits display signposts from radio light to x-ray light of activity that vastly exceeds our Sun. We inspect two such systems to determine whether the region responsible for this emission is on one of the component stars or in an interaction between the stars is not established. If the extreme activity from a component star, then it establishes an upper limit on the most extreme space weather a star like our Sun could produce under rapid rotation.

To estimate the location of the region of activity, we combine the signals received by radio telescopes from across the world with a technique called Very Long Baseline Interferometry (VLBI), resulting in the most magnification power currently possible. We confirm the radio emission is located on a particular star in one such system, not an interaction region. In a second system, we closely examine the data for signs of source motion such as from an oversized solar flare.