complex than a simple dipole. For example, the pulse profiles of X-ray Dim Isolated Neutron Stars may be explained by the addition of higher order multipoles (Zane & Turolla 2006). Also, magnetars are thought to require large toroidal fields to fuel their bursting activity (e.g., Thompson & Duncan 2001). The most striking example of a NS undergoing magnetar-like bursts is SGR 0418+5729, whose observed dipole field ($\lo 8\times 10^{12}$G) is much too low compared with typical magnetars, and therefore a significant hidden field must be present to power it (Rea et al. 2010; Turolla et al. 2011).

The central compact object (CCO) PSR J1852+0040 in the Kesteven 79 supernova remnant is another source with unusual properties (Halpern & Gotthelf 2010). Specifically, while its dipole surface magnetic field is inferred via $P$-$\dot{P}$ measurement ($P=0.105$ s, $\dot P=8.7\times 10^{-18}~\mathrm{s~s^{-1}}$) to be only $\sim 3.1\times10^{10}$ G, its pulse profile presents with an unusually high pulse fraction ($64\pm 2\%$), which implies large temperature anisotropy (concentrated hot spots) on its surface. Such hot spots are unattainable by anisotropic heat conduction at the observed dipole field strength. Also, since the spindown luminosity is much smaller than the X-ray luminosity, they cannot be produced by heating from 