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

TL;DR

This paper reports the discovery of polarized molecular bands in the second known DQ white dwarf, GJ 841B, revealing its magnetic field and temperature, and compares it with the first such object, G99-37.

Contribution

It provides the first polarization detection in the C_2 Swan bands of a white dwarf and models the magnetic field and temperature of GJ 841B.

Findings

GJ 841B shows polarized CH molecular bands and a magnetic field of 1.3 MG.

G99-37's magnetic field is estimated at 7.3 MG.

The temperature of GJ 841B is about 6100 K.

Abstract

We report a discovery of the circularly polarized CH $A^2\Delta-X^2\Pi$ and $B^2\Sigma^- -X^2\Pi$ 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.