Constraint on parameters of the Inverse Compton Scattering model for
  radio pulsars
  The inverse Compton scattering (ICS) model can explain various pulse profile
shapes and diversity of pulse profile evolution based on the mechanism that the
radio emission is generated through inverse Compton scattering between
secondary relativistic particles and radio waves from polar gap avalanches. In
this paper, we study the parameter space of ICS model for 15 pulsars, which
share the common pulse profile evolution phenomena that the pulse profiles are
narrower at higher observing frequencies. Two key parameters, the initial
Lorentz factor and the energy loss factor of secondary particles are
constrained using the least square fitting method, where we fit the theoretical
curve of the "beam-frequency mapping" of the ICS model to the observed pulse
widths at multiple frequencies. The uncertainty of the inclination and viewing
angles are taken into account in the fitting process. It is found that the
initial Lorentz factor is larger than 4000, and the energy loss factor is
between 20 and 560. The Lorentz factor is consistent with the prediction of the
inner vacuum gap model. Such high energy loss factors suggest significant
energy loss for secondary particles at altitudes of a few tens to hundreds of
kilometers.
