High-energy gamma-ray emission from the accreting black hole V404 Cygni
V404 Cygni is a close X-ray binary system composed of an about 10-solar mass
black hole accreting matter from a solar mass companion star. After nearly
26 years of quiescence, V404 Cygni underwent an exceptional outburst in 2015
for around ten days during which it became the brightest X-ray source in the
sky (see INTEGRAL POM
July &
November 2015).
This rare event was intensively monitored at all wavelengths (see Figure and,
e.g., INTEGRAL POM
July 2016).
The radio emission traces the jet activity (upper panel of the Figure) as
measured by OVRO and AMI radiotelescopes. The brightest radio flare occurred a
few hours before a high-energy gamma-ray emission detected by the Fermi Large Area
Telescope (second panel). The most significant emission period, as indicated by
the Test Statistic (third panel), is highlighted as a blue region in coincidence
with the brightest hard X-ray flare measured by INTEGRAL/IBIS/ISGRI in the
80-150 keV band (fifth panel).
The detection of high-energy gamma-ray production is a first for a so-called
low-mass X-ray binary. It is contemporaneous with the possible electron/positron
annihilation (Siegert et al. 2016, fourth panel) which may indicate that the
emitting region is located further away along the jet in order to avoid being
absorbed via pair production mechanism. This discovery would support the presence
of high-energy gamma-ray emission associated with ejections in X-ray binaries.
Reference:
"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
2016, Monthly Notices of the Royal Astronomical Society: Letters, Volume 462,
Issue 1, p.L111-L115
http://mnrasl.oxfordjournals.org/content/462/1/L111
