Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21360203p&link_type=abstract
American Astronomical Society, AAS Meeting #213, #602.03
Astronomy and Astrophysics
Astronomy
Scientific paper
The class of magnetically active binary star systems known as RS-CVn stars emit very brightly at radio wavelengths via gryo-synchrotron radiation. The quiescent flux of these stars exceeds that of the sun by 4-6 orders of magnitude; however, there is a strong correlation between xray and radio flux from early- to late-type stars, implying some similarity between the processes producing the emission. To date, the morphology of the magnetospheres of these stars, and extrasolar stars in general, has been inferred. Here we present the results of a multi-epoch 15GHz VLBI survey of the binary system Algol, in which we produce high-resolution, high-SNR maps of Algol's magnetosphere. By phase-referencing our data to a nearby phase calibrator using a rapid switching time, we obtain sub-milliarcsecond precision astrometric positions that, when combined with previous astrometric VLBI studies of the system, allow us to accurately position the radio emission with respect to the members of the Algol system, the first time this has been possible for any extrasolar stellar system. In one epoch we were able to able to image a full coronal loop, and we find that the structure of the radio corona consistently conforms to a two-lobed emission pattern centered on the secondary in the pair, oriented along the polar axis, and slightly offset toward the primary, implying that this coronal loop is a stable feature of Algol's magnetosphere. We would like to acknowledge the National Radio Astronomy Observatory for providing funding for this research through the National Science Foundation.
Goss Miller
Mutel Robert L.
Peterson William
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