NOTE ON HARTLE-HAWKING VACUA

The purpose of this Rapid Communication is to establish the basic prop erties-regularity at the horizon, time independence, and thermality-of the generalized Hartle-Hawking vacua defined in static spacetimes wit h a bifurcate Killing horizon admitting a regular Euclidean section. T hese states, for free or interacting fields, are defined by a Euclidea n functional integral on half the Euclidean section. The emphasis is o n generality, and the arguments are simple but formal.