CrH molecule: new diagnostic tool for measuring magnetic fields in ultra-cool dwarfs

Kuzmychov Oleksii, oleksii.kuzmychov@kis.uni-freiburg.de, Kiepenheuer-Institut fur Sonnenphysik Germany
Berdyugina Svetlana, sveta@kis.uni-freiburg.de, Kiepenheuer-Institut fur Sonnenphysik

Abstract
We investigated the Paschen-Back effect in the CrH molecule, and we examined its potential for the estimation of magnetic fields in substellar objects. The quantum mechanical calculations were done in order to calculate the frequencies of the electronic transitions and their strengths both in the absence and in the presence of a magnetic field. Employing these results and solving the transport equation for polarized stellar radiation numerically, we calculated the Stokes parameters produced by a number of CrH lines in the wavelength range 8600 ? 8700 A in dependence of the strength and orientation of the magnetic field. We show that the CrH lines produce a considerable polarization signal, especially Stokes V/Ic, at the magnetic field strengths 0.5?10 kG. Furthermore, the polarization signal shows a substantial asymmetry that originates from the Paschen-Back effect in the molecular lines. Because this asymmetry does not depend on the filling factor, but only on the magnetic field strength, the approach considered provides a sensitive tool for measuring magnetic fields on cool dwarfs.