2120011

This proposal is to use INTEGRAL/ISGRI to observe the 2024 periastron passage of gamma-ray binary PSR B1259-63 within the framework of a large multi-wavelength campaign (MeerKAT ATCA SALT VLT FERMI) whereradio extensive monitoring with MeerKAT has already been approved with a high priority. The previous monitoringof the previous periastron passage in 2021 with Swift/XRT shown the presence of the strong correlation of soft X-rayand radio emission up to ~30 d after the periastron and consequent disappearance of the correlation. The observedbehaviour could be interpreted in terms of scenario suggesting that the radio/X-ray emission is produced by differentpossible spatially separated populations of electrons or by a single electrons population strongly modified by coolingprocesses (Chernyakova et al. 5).With 750 ksec INTEGRAL/ISGRI observations we aim at the detailed studies of the post-periastron behaviourof PSR B1259-63 in terms of hard X-ray/radio lightcurves correlation. The proposal will allow us to answer thefollowing questions (i): if there is a time delay between radio and hard X-ray emission (ii): if the correlation ofthe radio/hard X-ray emissions persists through the whole periastron passage. Consequently the observations couldallow us to select between the proposed scenarios as well as study the structure of the Be star disk and the detailsof the interaction of the pulsar and the stellar wind. The proposed observations combined with Swift/XRT data willalso help us to study the evolution of the spectrum of this source at different orbital phases. Such studies are of agreat importance for the multiwavelength spectral modelling of this source. [truncated! Please see actual data for full text]