Photospheric Hanle diagnostic of weak magnetic dipoles in stars

Aims. We propose and explore a new diagnostic technique based upon the linear polarization emitted in Hanle-sensitive lines in disk-integrated stars where a dipolar magnetic field breaks the rotational symmetry of the resonance scattering polarization Methods. A star with a simple dipolar field and a 1-0 spectral line were used to compute polarization amplitudes and angles. Results. Predicted amplitudes are low but within reach of present instruments Conclusions. A new application of the Hanle effect is proposed and analyzed as a tool that allows measuring of some of the weakest stellar magnetic fields.