Joint Astrophysics/Space Physics Seminar

November 7, 2017 - 12:30pm
309 VAN

"A Search for Thermal Gyrosynchrotron Emission from Hot Stellar Coronae" by, Professor Robert Mutel, Department of Physics & Astronomy, The University of Iowa

Abstract:  We have conducted a search for thermal gyro-synchrotron (GS) radio emission from a sample of eight radio-loud stars whose X-ray coronae contain a hot (T > 107 K) component. We used the JVLA to measure Stokes I and V spectral energy distributions (SEDs) over the frequency range 15 - 45 GHz, fitting for best-fit models parameters using both power-law and thermal gyrosynchrotron emission models. For five of the eight stars (Algol, UX Arietis, HR1099, AD Leo), the SEDs were well-fit by a power-law GS model, with no evidence for a thermal component. However, for three stars (V410 Tau, HDE 283572, and UV Ceti), the SEDs had a circularly polarized enhancement above 30 GHz that was inconsistent with a pure power-law electron distribution. These spectra were well-fit by summing the emission from an extended coronal region with power-law GS emission and a smaller region with hotter thermal plasma and much stronger magnetic fields emitting thermal GS emission. The inferred magnetic fields range from 1000 - 2500 gauss in these hot coronal regions.