GJ 841B - The Second DQ White Dwarf with Polarized CH Molecular Bands

We report a discovery of the circularly polarized CH $A^2\mathrm{\Delta }-X^2\mathrm{\Pi }$ and $B^2{\mathrm{\Sigma }}^{-}-X^2\mathrm{\Pi }$ molecular bands in the spectrum of the DQ white dwarf GJ 841B. This is only the second such object since the discovery of G99-37 in the 1970s. GJ 841B is also the first WD to unambiguously show polarization in the C_2 Swan bands. By modeling the intensity and circular polarization in the CH bands we determine the longitudinal magnetic field strength of 1.3 ± 0.5 MG and the temperature of 6100 ± 200 K in the absorbing region. We also present new observations of G99-37 and obtain estimates of the magnetic field strength 7.3 ± 0.3 MG and temperature 6200 ± 200 K, in good agreement with previous results.