  We consider the response of an Unruh-DeWitt detector near an extremal charged
black hole, modeling the near-horizon region of this extremal spacetime by the
Bertotti-Robinson spacetime. The advantage of employing the Bertotti-Robinson
limit is that the two-point functions for a massless scalar field are
obtainable in closed form for the field in a number of quantum states of
interest. We consider the detector coupled to a massless field in both the
Boulware vacuum state and arbitrary thermal states, including the
Hartle-Hawking state, and analyse the detector's response for a broad range of
trajectories. Particular attention is paid to the thermalization of the
detector, the anti-Unruh and anti-Hawking effect.
