# High-energy gamma-ray activity from V404 Cygni detected by AGILE during the 2015 June outburst

## TL;DR

The AGILE satellite detected transient high-energy gamma-ray emission from V404 Cygni during its June 2015 outburst, correlating with radio and X-ray flares and suggesting jet activity in a microquasar scenario.

## Contribution

This study reports the first detection of high-energy gamma-ray emission from V404 Cygni during an outburst, linking gamma-ray activity with jet ejections in a microquasar.

## Key findings

- Gamma-ray emission detected at 50-400 MeV with 4.3σ significance.
- Correlation between gamma-ray activity and radio/X-ray flares.
- Enhanced 511 keV line emission indicating plasmoid ejections.

## Abstract

The AGILE satellite detected transient high-energy gamma-ray emission from the X-ray binary V404 Cygni, during the June 2015 outburst observed in radio, optical, X-ray and soft gamma-ray frequencies. The activity was observed by AGILE in the 50-400 MeV energy band, between 2015-06-24 UT 06:00:00 and 2015-06-26 UT 06:00:00 (MJD 57197.25 - 57199.25), with a detection significance of ${\sim}4.3{\sigma}$. The gamma-ray detection, consistent with a contemporaneous observation by Fermi-LAT, is correlated with a bright flare observed at radio and hard X-ray frequencies, and with a strong enhancement of the 511 keV line emission, possibly indicating plasmoid ejections in a lepton-dominated transient jet. The AGILE observations of this binary system are compatible with a microquasar scenario in which transient jets are responsible for the high-energy gamma-ray emission.