The temporal decay of the flux components of Transient Anomalous X-ray Pulsar
XTE J1810-197 following its 2002 outburst presents a unique opportunity to
probe the emission geometry of a magnetar. Toward this goal, we model the
magnitude of the pulsar's modulation in narrow spectral bands over time.
Following previous work, we assume that the post-outburst flux is produced in
two distinct thermal components arising from a hot spot and a warm concentric
ring. We include general relativistic effects on the blackbody spectra due to
gravitational redshift and light bending near the stellar surface, which
strongly depend on radius. This affects the model fits for the temperature and
size of the emission regions. For the hot spot, the observed temporal and
energy-dependent pulse modulation is found to require an anisotropic,
pencil-beamed radiation pattern. We are able to constrain an allowed range for
the angles that the line-of-sight (psi) and the hot spot pole (xi) make with
respect to the spin-axis. Within errors, this is defined by the locus of points
in the xi-psi plane that lie along the line (xi+beta(R))(psi+beta(R)) ~
constant, where beta(R) is a function of the radius R of the star. For a
canonical value of R=12 km, the viewing parameters range from psi=xi=37 deg to
(psi,xi)=(85 deg,15 deg). We discuss our results in the context of magnetar
emission models.Comment: 8 pages, accepted to Ap