Magnetic cycles of tidally deformed red dwarfs reveal new stellar behavior

Star system: CD-28 1030 | Distance from the Sun: 63.9 light years

M dwarfs are small, cool stars that can become tidally deformed when they are part of close binary systems called cataclysmic variables. These distortions change the stars’ shapes and may affect how their magnetic fields are generated. Studying these effects helps scientists understand stellar dynamos and magnetic activity in stars beyond our Sun.
This study examined the relationship between the magnetic cycle period and the rotation period in tidally distorted M dwarfs. The researchers found that, unlike single M dwarfs, those in cataclysmic variables show an anti-correlation: as the rotation period increases, the cycle period also becomes longer. This suggests that tidal deformation changes how magnetic fields are produced in these stars.
Numerical simulations revealed that in highly distorted M dwarfs, thermal convection and differential rotation are both weakened. These changes may slow down the process that converts poloidal magnetic fields into toroidal ones, providing a possible explanation for the observed relationship between cycle and rotation periods.
Key findings

 
Tidally distorted M dwarfs in cataclysmic variables show an anti-correlation between cycle and rotation periods.
 
Single M dwarfs do not display this relationship.
 
Greater stellar deformation leads to longer magnetic cycle periods.
 
Simulations indicate weakened convection and reduced differential rotation in distorted stars.
 
These effects may explain changes in magnetic field generation in non-spherical stars.

Scientific study

Retarded Stellar Dynamo in Tidally Deformed M Dwarfs (external link)