Radio and gamma-ray emissions from pulsars: possible observational tests

TL;DR

This paper reviews observational tests for pulsar radio and gamma-ray emission models, demonstrating how frequency-dependent pulse profile evolution supports the inverse Compton scattering model and how gamma-ray emission locations can be constrained geometrically.

Contribution

It provides observational tests for pulsar emission models, linking pulse profile evolution to the inverse Compton scattering model and constraining gamma-ray emission sites.

Findings

Pulse profile evolution can be explained by the ICS model.

Different emission components originate from different heights at various frequencies.

Gamma-ray emission locations are consistent with the annular gap and outer gap models.

Abstract

Many models for the pulsar radio and $\gamma$-ray emissions have been developed. The tests for these models using observational data are very important. Tests for the pulsar radio emission models using frequency-altitude relation are presented in this paper. In the radio band, the mean pulse profiles evolve with observing frequencies. There are various styles of pulsar profile - frequency evolutions (which we call as "beam evolution" figure), e.g. some pulsars show that mean pulse profiles are wider and core emission is higher at higher frequencies than that at lower frequencies, but some other pulsars show completely the contrary results. We show that all these "beam evolution" figures can be understood by the Inverse Compton Scattering(ICS) model (see Qiao at al.2001 also). An important observing test is that, for a certain observing frequency different emission components are radiated from the different heights. For the $\gamma$-ray pulsars, the geometrical method (Wang et al. 2006) can be used to diagnose the radiation location for the $\gamma$-ray radiation. As an example, Wang et al. (2006) constrain the $\gamma$-ray radiation location of PSR B1055-52 to be the place near the null charge surface. Here we show that Wang's result matches the proposed radiation locations by the annular gap model as well as the outer gap models.