HEAD 2003 Meeting
Session 12. Protostars, Stars and Instrumentation III
Poster, Sunday-Wednesday, March 23, 2003, Duration of Meeting

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[12.01] The Radio Spectrum of Capella

R. A. Osten (NRAO), G.M. Harper, A. Brown (CASA, University of Colorado)

Capella's soft X-ray and EUV spectrum are dominated by emission lines and continua from high temperature, T \approx 6-8 MK plasma. In contrast to most other X-ray bright late-type stellar sources, whose radio emissions are due to nonthermal processes, Capella's radio emission appears to be dominated by thermal bremsstrahlung radiation from the same high temperature plasma that produces copious X-rays. Radio and X-ray observations of thermal bremsstrahlung emission offer complimentary information on the distribution of the high temperature plasma. During the Emission Line Project observations of Capella with the Chandra X-ray Observatory in 1999 September, simultaneous observations of Capella were performed with the LETGS, EUVE, HST/STIS, and the VLA spanning an order of magnitude in frequency. Contemporanous observations with the HETGS were also performed. We report on modelling the differential emission measure distribution from chromospheric to coronal temperatures, and comparison of predicted radio fluxes with observed fluxes. The spectrum of excess radio emission is investigated to look for evidence of gyroresonance or gyrosynchrotron emission.

RAO acknowledges support from NRAO through a Jansky fellowship.

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Bulletin of the American Astronomical Society, 35#2
© 2003. The American Astronomical Soceity.