Broad-band high energy emission from the black-hole binary V404 Cyg
The black-hole binary V404 Cyg, which entered the outburst phase in
June 2015, after 26 years of quiescence (see also INTEGRAL POMs of
July &
November 2015 and
July &
October 2016).
The source encountered extreme accretion rates and reached extreme
luminosities, and showed different kinds of outflows in the X-ray,
optical and radio bands.
The image shows the Swift/XRT (red) + INTEGRAL/JEM-X (purple) +
INTEGRAL/IBIS-ISGRI (clear blue) high energy emission spectrum of
V404 Cyg. Shown also is the spectrum of the dust scattering halo as
seen by Swift/XRT (orange), that formed around the source during the
outburst as a consequence of the bright flares produced by the source
and of the presence of dust layers along the line of sight, between
the system and Earth (see, e.g.,
NASA's Swift Reveals a Black Hole Bull's-eye).
The spectrum of the source V404 Cyg was fitted with a model including
the so-called "MYTORUS" model (see
Yaqoob T. 2012, MNRAS, 423, 3360), which assumes that the X-ray
emission from a point source is heavily reprocessed by a toroidal,
non-uniform, high-density absorber surrounding it. This configuration
seems so far to be the only model able to explain the extremely peculiar
behaviour of V404 Cyg as compared to other black-hole binaries. The thick
white line marks crossing the coloured points marks the best fit to the
data. The flat solid white lines indicate the illuminating Compton continuum
and the power-law component describing the dust scattering halo emission. The
dashed line marks the transmitted emission (the emission that survived the
absorption from the toroidal reprocessor), the dot-dashed lines mark the
scattered continuum, whereas the dotted line marks the fluorescent Fe line
spectra and the Nickel line at about 7.5 keV.
Reference:
"The black hole binary V404 Cygni: an obscured AGN analogue",
S.E. Motta, J.J.E. Kajava, C. Sánchez-Fernández, M. Giustini & E. Kuulkers,
MNRAS, in press
https://arxiv.org/abs/1607.02255
