Study for Curvature Radiation and Magnetic Pair-creation Process on Polar-cap Region of Magnetic White Dwarf
Year: 2026
Type: article
Abstract: Rapidly rotating, strongly magnetized white dwarfs (WDs) have been proposed as potential sites of rotation-powered activity analogous to that of a neutron star pulsar. In this study, we investigate particle acceleration, radiation processes, pair creation, and resulting synchrotron radiation in the polar-cap acceleration region. Within the framework of the space-charge-limited flow model, we examine how these processes depend on the spin period and surface magnetic field using both one-dimensional numerical calculations and analytical estimates. To explore the impact of the magnetic field geometry on the accelerating process, we consider both a pure dipole field and a combination of dipole and quadrupole fields. The inclusion of a quadrupole component reduces the curvature radius of the magnetic field lines and significantly enhances the accelerating field, leading to more efficient radiation and pair-creation processes. Using this framework, we evaluate the WD death line with a more consistent treatment of the relevant physical processes than the previous studies. We find that the pair-creation process can occur for spin periods P ≲ 100 s, when the dipole field strength B *, d ≲ 10 10 G, indicating that pair creation is difficult to sustain in currently known magnetic WDs. We discuss the implications of our model for rotation-powered activity in rapidly spinning isolated magnetic WDs and for the possible WD interpretation of long-period radio transients.
Source: The Astrophysical Journal
Authors: Bingyan Wang, Jumpei Takata
Institution: Huazhong University of Science and Technology
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
OpenAlex ID: W7168150532