Comments on the magnetic field structure of the star CU Virginis

Abstract

The model of the magnetic field structure of the CP2 star CU Vir (HD 124224) constructed by the method of “magnetic charge (MCD-method) has shown that it is consistent with the model of a displaced dipole. The displacement from the center of the star to the negative monopole is $d = 0.3$ of the radius, the inclination angle of the dipole axis to the rotational axis is $\beta = 87^{\rm o}$, and the field strength at the poles amounts to $B_{\rm p}(-) = 7.9$ kG and $B_{\rm p}(+) = 1.2$ kG. The mean surface magnetic field varies within 1.2–3.2 kG. The dipole axis points away from the zero meridian by an angle of $+30^{\rm o}$. Using the MCD-method we derived the distribution of the field intensity over the surface, which has been compared to the distribution of the chemical elements He and Si, taken from literature. Silicon has turned out to concentrate around the strong negative magnetic pole, whereas helium concentrates in the region of the weak positive pole, where the orientation of magnetic lines of force is mostly vertical. The presence of a double silicon spot suggests a more complex magnetic field structure than the dipolar one, however, the small number of data makes it impossible so far to confirm such an assumption.