High-energy gamma-ray observations of the accreting black hole V404 Cygni during its 2015 June outburst

A. Loh*, S. Corbel, G. Dubus, J. Rodriguez, I. Grenier, T. Hovatta, T. Pearson, A. Readhead, R. Fender, K. Mooley

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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We report on Fermi/Large Area Telescope observations of the accreting black hole low-mass X-ray binary V404 Cygni during its outburst in 2015 June-July. Detailed analyses reveal a possible excess of γ -ray emission on 2015 26 June, with a very soft spectrum above 100 MeV, at a position consistent with the direction of V404 Cyg (within the 95 per cent confidence region and a chance probability of 4 × 10-4). This emission cannot be associated with any previously known Fermi source. Its temporal coincidence with the brightest radio and hard X-ray flare in the light curve of V404 Cyg, at the end of the main active phase of its outburst, strengthens the association with V404 Cyg. If the γ -ray emission is associated with V404 Cyg, the simultaneous detection of 511 keV annihilation emission by INTEGRAL reqires that the high-energy γ -rays originate away from the corona, possibly in a Blandford-Znajek jet. The data give support to models involving a magnetically arrested disc where a bright γ -ray jet can re-form after the occurrence of a major transient ejection seen in the radio.

Original languageEnglish
Pages (from-to)L111-L115
Number of pages5
Issue number1
Publication statusPublished - 11 Oct 2016
MoE publication typeA1 Journal article-refereed


  • Black hole physics
  • Gamma-rays: stars
  • Radio continuum: stars
  • Stars: individual: V404 Cygni
  • X-rays: binaries

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