Energy Loss of Newborn Magnetars by Schwinger Process

We investigate electron–positron pair creation through the Schwinger process in newborn magnetars with millisecond spin periods and surface dipole fields close to or above the QED critical field, $B_{\mathrm{Q}}=4.414\times {10}^{13}\mathrm{G}$. In the unscreened field scenario, we derive the analytical global pair creation flux and recast it into a compact form with accurate analytic approximations. For a fiducial model with $B_{\mathrm{p}}={10}^{14}\mathrm{G}$ and $P_0=1\mathrm{m}\mathrm{s}$, the Schwinger channel exceeds the classical Goldreich–Julian particle supply by many orders of magnitude and becomes the dominant source of charges at the earliest stage of the magnetar. The associated discharge removes about $90\mathrm{\%}$ of the initial rotational energy within 30 ms, suppresses the gravitational-wave loss channel, and implies that the observable millisecond phase is extremely short in this unscreened scenario. The rapid energy release over such a short timescale may also provide a viable power source for astrophysical transients. Extending the same fiducial model to ${10}^4\mathrm{y}\mathrm{r}$ gives spin periods of order seconds, linking newborn millisecond magnetars to the mature magnetar population.