event
Thursday 03 Jul 2008: Zeeman Doppler imaging and differential rotation in a pre- main sequence binary system
Dr Nick Dunstone - University of St Andrews
Physics, 4th Floor interaction area 13:00-14:00
I present the first surface magnetic field maps and differential rotation measurements of a pre-main-sequence binary system. The radial magnetic maps of HD 155555 (G5IV + K0IV) reveal a complex surface magnetic topology with mixed polarities at all latitudes and rings of azimuthal field present on both stars. We examine the evolution of the relative field strengths between observations in 2004 and 2007 and suggest that the observed changes could be indicative of a magnetic activity cycle. Using the same dataset we measure the differential rotation rate of brightness and magnetic features. Both stellar components of HD 155555 are found to have rates of differential rotation similar to those of the same spectral type main-sequence single stars. This is in contrast to previous work on evolved binary systems where low rates of differential rotation were reported. I will discuss possible explanations for this.
