V404 Cygni with Fermi-LAT

TL;DR

This study reanalyzed 11.5 years of Fermi-LAT data for V404 Cygni and found no gamma-ray emission during its outburst, attributing previous claims to source confusion with a nearby blazar.

Contribution

The paper provides a comprehensive reanalysis with updated data and models, clarifying the absence of gamma-ray emission from V404 Cygni during outburst periods.

Findings

No gamma-ray excess detected during outburst

Previous claims likely due to source confusion

Updated analysis rules out high-energy emission from V404 Cygni

Abstract

We revisit the well-studied outburst of the low mass X-ray binary (LMXB) system V404 Cygni, and claims of gamma-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 gamma-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 gamma-ray emitting blazar B2023+336, a luminous source approximately 0.3 degrees away, which causes source confusion at the position of V404 Cygni, the luminous gamma-ray background, and the use of older background models and catalogues in previous studies.