Speaker
Description
Accreting magnetic white dwarfs offer a unique window into accretion physics in binary systems. Like X-ray binaries, they harbour a standard Shakura-Sunyaev accretion disc whose inner edge can be magnetically truncated, yet their lower energies and longer dynamical timescales make the inner accretion geometry far more accessible. I will present results on DW Cnc, a well-studied intermediate polar that has recently revealed a remarkable suite of new phenomena. We report a new micronova burst detected by ASAS-SN reaching a peak optical luminosity of 6.6×10³³ erg s⁻¹ with a released energy consistent with a thermonuclear runaway in the magnetically confined accretion flow. Immediately preceding the burst, TESS and OPTICAM data reveal the reappearance of tilted disc precession as DW Cnc emerges from its low state. Strikingly, we also identify a new phenomenon in which the white dwarf spin signal switches on and off during the precession period, providing the first evidence for pole flipping in a disc-accreting system. These results place DW Cnc at the intersection of two poorly understood phenomena, micronovae and accretion column dynamics, and highlight the need for systematic monitoring of magnetic systems beyond serendipitous discovery. Here I will discuss how NewAthena will transform our ability to probe the inner accretion geometry of magnetic white dwarfs. In particular I will show how measurements of time-resolved velocity shifts in the Fe XXV/XXVI lines at eV precision will allow us to directly test competing models of disc–magnetosphere coupling and definitively distinguish pole switching from continuous accretion column precession.
