V404 Cygni with Fermi-LAT

Abstract

We revisit the well-studied outburst of the low mass X-ray binary (LMXB) system V404 Cygni, and claims of 𝛾-ray excesses observed with the Fermi-LAT instrument. Upon analysing an 11.5 year dataset with the 8-year LAT point source catalogue and 8-year background models, we find no evidence to suggest that there is high energy 𝛾-ray emission during the outburst period (or at any other time) from V404 Cygni. This is due to the proximity of V404 Cygni to the 𝛾-ray emitting blazar B2023+336, a luminous source approximately 0.3°away, which causes source confusion at the position of V404 Cygni, the luminous 𝛾-ray background, and the use of older background models and catalogues in previous studies.