Magnetic activity and dynamic phenomena in close binaries
Hydromagnetic dynamos in close binaries with outer convective envelopes produce large scale and intense magnetic fields which affect all atmospheric levels, from the photosphere to the chromosphere and corona. In the photosphere, magnetic fields give rise to huge cool structures, similar to sunspots...
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| Format: | Conference item |
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2001
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| Summary: | Hydromagnetic dynamos in close binaries with outer convective envelopes produce large scale and intense magnetic fields which affect all atmospheric levels, from the photosphere to the chromosphere and corona. In the photosphere, magnetic fields give rise to huge cool structures, similar to sunspots, which are called starspots. Their surface distribution and area changes can be used to study stellar rotation and activity cycles. The information on cycle lengths and differential rotation can be complemented with observations of the orbital period modulation in eclipsing systems. We discuss the recently proposed connection between the activity cycles and the modulation of the orbital period based on the variation of the gravitational quadrupole moment of the active component as a consequence of the redistribution of the kinetic and magnetic energies in its interior along the activity cycle. The variation of the gravitational potential felt by the companion can explain the observed variations of the orbital period of the order of DeltaP/P similar to 10(-6) - 10(-5). We present some recent results obtained by the study of a sample of late-type binaries and discuss their implication for the energy balance of hydromagnetic dynamos. |
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