  We study the conformal data of a generic superconformal half-BPS line defect
in a four-dimensional $\mathcal{N} = 2$ theory. We prove a theory independent
relation between the one-point function of the stress tensor in the presence of
the line defect and the two-point function of the displacement operator. When
the defect is interpreted as a heavy charged particle in a gauge theory, the
result relates the energy emitted through Bremsstrahlung with the coupling of
the stress tensor to the particle at rest.
