Lyman and Balmer Continuum Spectra for Hydrogen Atoms in Strong White Dwarf Magnetic Fields

Abstract

Abstract We report calculations of photoionization cross sections for hydrogen atoms in white-dwarf magnetic fields. The calculations were implemented using the adiabatic-basis-expansion method and the coupled-channel theory, which are valid for low and high magnetic fields, respectively. The magnetic fields span over a typical white-dwarf strength regime from 23.5 to 2350 MG. Lyman and Balmer continuum spectra for bound–free transitions in magnetic white-dwarf stars are presented with various field strengths. The current results are compared with those from the complex-rotation method. Excellent agreement is shown in the energy region away from Landau thresholds, but the pronounced discrepancies are found in the small vicinity below Landau thresholds. The agreement shown illustrates the reliability of these two theoretical approaches used, while the discrepancies should be attributed to the limitation of the complex-rotation method. The photoionization cross sections presented here should be applicable to the analyses of continuum spectra and their polarization properties observed in the atmospheres of hydrogen-dominated magnetic white dwarfs.