Origin of the broad band emission from gamma-ray binaries with a radio pulsar

Gamma-ray binaries are a subclass of high-mass binary systems whose energy spectrum peaks above 100 MeV and extends up to very high energy (TeV) gamma-rays. Currently, fewer than ten such systems were discovered in the gamma-ray band by the current generation of Cherenkov telescopes. Therefore gamma-ray binaries represent a relatively new and unexplored class of astrophysical object. Of all the binary systems that are regularly observed at TeV energies, the nature of the compact object is firmly established for only two systems, PSR B1259-63 and PSR J2032+4127. For all other systems, the nature of their compact object is so far unknown. Thus it is highly important to study the details of timing and spectral properties over the broad band (radio to TeV) emission from these two systems, as it would allow a detailed scalable physical model, which can be compared with the emission observed from other systems, to be built. In my talk I will compare properties of these two systems comparing the results of the 2017 periastron passage in PSR J2032+4127 with the results accumulated during more than two decades of observations of PSR B1259-63, and discuss the possible theoretical implications of these observations. Intensive multi-wavelength observations of both systems allowed to propose a model in which the disc of the Be star is inclined to the orbital plane and X-ray and TeV emission originates from synchrotron and inverse Compton emission of pulsar wind electrons accelerated at the shock. Despite these similarities the higher spin-down luminosity of PSR B1259-63 and its larger/denser disk significantly changes the magnetic field in the emission region and the details of the particle acceleration leading to a drastically different behavior of the two systems in the GeV domain. Knowledge of the disk clumping and bremsstrahlung emission in PSR B1259-63 allows the origin of the mysterious GeV flares in PSR B1259-63 to be explained.