Spectrum evolution in binary pulsar B1259-63/LS 2883 Be star and gigahertz-peaked spectra

TL;DR

This study investigates how the radio spectrum of pulsar PSR B1259-63 varies with orbital phase, suggesting environmental interactions like free-free absorption and cyclotron resonance influence its spectral evolution, which may shed light on gigahertz-peaked spectra in pulsars.

Contribution

The paper introduces a qualitative model explaining spectral evolution of PSR B1259-63 based on environmental effects, advancing understanding of pulsar spectra.

Findings

Spectral shape depends on orbital phase.

Environmental interactions affect radio wave propagation.

Proposed mechanisms include free-free absorption and cyclotron resonance.

Abstract

We study the radio spectrum of PSR B1259-63 orbiting around the Be star LS 2883 and show that the shape of the spectrum depends on the orbital phase. At frequencies below 3 GHz PSR B1259-63 flux densities are lower when measured near the periastron passage than those measured far from periastron. We suggest that an interaction of the radio waves with the Be star environment accounts for this effect. While it is quite natural to explain the pulsar eclipse by the presence of an equatorial disk around LS 2883, this disk alone cannot be responsible for the observed spectral evolution of PSR B1259-63 and we, therefore, propose a qualitative model which explains this evolution. We consider two mechanisms that might influence the observed radio emission: free-free absorption and cyclotron resonance. We believe that this binary system can hold the clue to the understanding of gigahertz-peaked spectra of pulsars.