207 research outputs found
The rise and fall of the compact jet in GRO J1655-40
In this work, we present some preliminary results on a multi-wavelength (radio/infrared/optical/X-ray) study of GRO J1655-40 during its 2005 outburst. We focus on the broadband spectral energy distribution during the different stages of the outburst. In particular, using this unprecedented coverage, and especially thanks to the new constraints given in the mid-IR by Spitzer, we can test the physical self-consistent disk-jet model during the hard state, where the source shows radio emission from a compact jet. The hard state broadband spectra of the observations during the decay of the outburst, are fairly well fit using the jet model with parameters overall similar to those found for Cyg X-1 and GX 339-4 in a previous work. However, we find that, compared to the other two BHs, GRO J1655-40 has a much higher jet power (at least a factor of 3), and that, most notably, the model seems to underestimate the radio emissio
Transient jet formation and state transitions from large-scale magnetic reconnection in black hole accretion discs
Magnetically arrested accretion discs (MADs), where the magnetic pressure in
the inner disc is dynamically important, provide an alternative mechanism for
regulating accretion to what is commonly assumed in black hole systems. We show
that a global magnetic field inversion in the MAD state can destroy the jet,
significantly increase the accretion rate, and move the effective inner disc
edge in to the marginally stable orbit. Reconnection of the MAD field in the
inner radii launches a new type of transient outflow containing hot plasma
generated by magnetic dissipation. This transient outflow can be as powerful as
the steady magnetically-dominated Blandford-Znajek jet in the MAD state. The
field inversion qualitatively describes many of the observational features
associated with the high luminosity hard to soft state transition in black hole
X-ray binaries: the jet line, the transient ballistic jet, and the drop in rms
variability. These results demonstrate that the magnetic field configuration
can influence the accretion state directly, and hence the magnetic field
structure is an important second parameter in explaining observations of
accreting black holes across the mass and luminosity scales.Comment: 5 pages, 3 figures, submitted to MNRAS Letter
The unique case of the AGN core of M87: a misaligned low power blazar?
M87 hosts one of the closest jetted active galactic nucleus (AGN) to Earth.
Thanks to its vicinity and to the large mass of is central black hole, M87 is
the only source in which the jet can be directly imaged down to near-event
horizon scales with radio very large baseline interferometry (VLBI). This
property makes M87 a unique source to isolate and study jet launching,
acceleration and collimation. In this paper we employ a multi-zone model
designed as a parametrisation of general relativistic magneto-hydrodynamics
(GRMHD); for the first time we reproduce the jet's observed shape and
multi-wavelength spectral energy distribution (SED) simultaneously. We find
strong constraints on key physical parameters of the jet, such as the location
of particle acceleration and the kinetic power. However, we under-predict the
(unresolved) {\gamma}-ray flux of the source, implying that the high-energy
emission does not originate in the magnetically-dominated inner jet regions.
Our results have important implications both for comparisons of GRMHD
simulations with observations, and for unified models of AGN classes.Comment: 12 pages, 7 figures, accepted for publication on MNRAS, comments are
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