Speaker
Description
We present a search for transient gamma-ray activity from the rapidly rotating, highly magnetized white dwarf ZTF J1901+1458 using Fermi-LAT data. We investigate the temporal behaviour of the source by analysing individual time intervals and identify several candidate episodes with test statistics corresponding approximately to the (3\sigma) significance regime. The candidate intervals show integrated photon fluxes of order (10^{-7})–(10^{-6}) ph cm(^{-2}) s(^{-1}), with the most significant interval reaching approximately 4$\sigma$. However, accounting for the large number of temporal trials substantially reduces the significance of the most significant individual excursion, and we therefore treat these intervals as candidate transient events rather than definitive detections. Nevertheless, the recurrence of candidate episodes motivates investigation of whether such activity could be connected to the extreme physical properties of ZTF J1901+1458, whose rapid rotation and strong magnetic field provide substantial rotational and magnetic energy reservoirs. We therefore investigate an alternative magnetospheric mechanism in which differential rotation generates magnetic stresses and an accelerating electric potential that injects non-thermal particles into the magnetosphere. For the adopted parameters, the model produces an accelerating potential of (\Delta V \simeq 5.53\times10^{11}) V, while a six-hour event requires a free magnetic energy of (\sim9.98\times10^{39}) erg, corresponding to a toroidal-to-poloidal field ratio of (\sim0.098) and a differential-rotation fraction of (\sim3.0\times10^{-4}). Stronger differential winding is expected to enter a nonlinear regime regulated by magnetic back-reaction. The resulting framework provides an alternative interpretation of the candidate gamma-ray activity and enables a self-consistent test of the available magnetic energy, particle acceleration, and subsequent radiative emission.