Speaker
Description
We asses the precision of the modeling of electromagnetic cascades using model calculations with publicly available Monte-Carlo codes CRPropa, CRbeam and ELMAG and compare their predictions with theoretical expectations. We find that model predictions of different codes differ by up to 50% for low-redshift sources, with discrepancies increasing up to order-of-magnitude level with the increasing source redshifts. We identify the origin of these discrepancies and demonstrate that after eliminating the inaccuracies found, the discrepancies between the three codes are reduced to 10% when modeling nearby sources with z~0.1. Our corrections were taken into account and implemented by developers of ELMAG and CRPropa in the new versions of their codes: CRPropa 3.2 and ELMAG 3.03. We argue that the CRbeam code provides reliable predictions for spectral, timing and imaging properties of the secondary gamma-ray signal for both nearby and distant sources with z~1. Finally, we use CRbeam and corrected CRPropa to set a lower bound on IGMF from time variability of 1ES 0229+200 and Fermi/LAT observations of the "pair echo" of GRB 221009A.
