High-resolution simulations of LS 5039

Abstract

Context. We present an analysis of our high-resolution relativistic hydrodynamics model of the stellar- and pulsar-wind interactions in the LS-5039 system. Aims. With our high-resolution simulation covering three orbital periods, we analyse the impact of turbulence with a particular focus on short-term and orbit-to-orbit variations. Methods. Our model uses a relativistic hydrodynamical description of the wind interaction in the LS-5039 system, assuming a pulsar wind-driven scenario. The corresponding system of equations was solved using the finite-volume code CRONOS. We computed the statistical quantities, which are also relevant for particle acceleration in this system, from the results of multiple consecutive timesteps. Results. In our simulation, we find that the previously observed shock structures related to the wind-collision region (WCR), including the pulsar-wind termination, are dynamically influenced by orbital motion. From our high-resolution simulation, we find high turbulence levels following from instabilities driven at the WCR. These instabilities lead to strong fluctuations of several dynamical quantities, especially around and after apastron. These fluctuations are expected to impact the particle transport and especially the related emission of non-thermal radiation. As an important example, the region for which gamma-ray emission has been found to be boosted due to relativistic beaming (in previous studies) shows strong variations in size both on short and orbital timescales. Conclusions. Using a large computational domain together with a high spatial resolution allowed us to carry out a detailed study of fluctuations in stellar- and pulsar-wind interactions. The results indicate a possible influence on the non-thermal emission from this system, which will be analysed with dedicated simulations in a forthcoming publication.