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We show that a pair of thermal, antipodal hot-spots on the neutron starsurface is able to fully account for the pulsar's double blackbody spectrum andenergy-dependent pulse profile, including the observed 180 degree phasereversal at approximately 1.2 keV. By comparing the observed pulse modulationand phase to the model predictions, we strongly constrain the hot-spot pole(xi) and the line-of-sight (psi) angles with respect to the spin axis. For anominal radius of R = 12 km and distance D = 2.2 kpc, we find (xi,psi) =(86d,6d), with 1-sigma error ellipse of (2d,1d); this solution is degenerate inthe two angles. The best-fit spectral model for this geometry requires that thetemperatures of the two emission spots differ by a factor of 2 and their areasby a factor of ~ 20. Including a cosine-beamed pattern for the emittedintensity modifies the result, decreasing the angles to (84d,3d); however thismodel is not statistically distinguishable from the isotropic emission case. Wealso present a new upper limit on the period derivative of Pdot < 3.5E-16(2-sigma), which limits the global dipole magnetic field to B_s < 2.0E11 G,confirming PSR J0821-4300 as an "anti-magnetar." We discuss the results in thecontext of observations and theories of nonuniform surface temperature onisolated NSs of both weak and strong magnetic field. To explain the nonuniformtemperature of PSR J0821-4300 may require a crustal field that is much strongerthan the external, global dipole field.

Modeling the Surface X-ray Emission and Viewing Geometry of PSR J0821-4300 in Puppis A