Strong signature of right-handed circularly polarized photoionization close to the cyclotron line in the atmosphere of magnetic white dwarfs
Year: 2024
Type: article
Abstract: Magnetic fields break the symmetry of the interaction of atoms with photons with different polarizations, yielding chirality and anisotropy properties. The dependence of the absorption spectrum on the polarization, a phenomenon known as dichroism, is present in the atmosphere of magnetic white dwarfs. Its evaluation for processes in the continuum spectrum has been elusive so far due to the absence of appropriate ionization equilibrium models and incomplete data on photoionization cross sections. We combined rigorous solutions to the equilibrium of atomic populations with approximate cross sections to calculate the absolute opacity due to photoionization in a magnetized hydrogen gas. We predict a strong right-handed circularly polarized absorption (χ+) formed blueward of the cyclotron resonance for fields from about 14 to several hundred megagauss. In energies lower than the cyclotron fundamental, this absorption shows a deep trough with respect to linear and left-handed circular polarizations that steepens with the field strength. The jump in χ+ is due to the confluence of a large number of photoionization continua produced by right-handed circularly polarized transitions from atomic states with a nonnegative magnetic quantum number toward different Landau levels.
Source: Astronomy and Astrophysics
Author: René D. Rohrmann
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,732
OpenAlex ID: W4405302806