Physical properties of the gamma-ray binary LS 5039

Abstract

We studied the LS 5039 gamma-ray binary in the 0.15-15 GHz range with both simultaneous and non-simultaneous data. From the non-simultaneous data we computed an average spectrum and found that it is best explained by Razin effect with p = 2.16±0.04 and νR = 0.42±0.02 GHz. We obtained two simultaneous spectra for 19 July 2013 and 21 July 2013. The first one was explained by SSA with p = 1.86 ± 0.01 while the second was explained by Razin effect with p = 2.28 ± 0.05 and νR = 0.44 ± 0.04 GHz. Therefore, we conclude that the Razin effect can vary to the point of vanishing completely. This, along with further variations in the spectral index, suggests the source experiences changes in either the synchrotron injection, electron density or magnetic field in the timescale of days and also timescales within the orbital period (3.906 d). Furthermore, the presence of the Razin effect supports a non-accreting pulsar scenario over a microquasar scenario. Finally, we suggest where further research should be directed towards