Hardness-intensity diagram: evolution of a
black hole outburst
During this phase, the behavior of
the jet, revealed by infrared and radio
observations, also begins to change.
The infrared emission drops almost
as soon as the state transition begins
(14 ), indicating a change in the jet
properties(density andmagneticfield)
close to the black hole.
The radio emission begins to vary
more dramatically, showing oscilla-
tions and flare events superposed on
an overall decline (8 , 15 ). At a cer-
tain point, there are one or more large
radio flares, which can be two or more
orders of magnitude more luminous
than the previous existing, steadier jet
in the hard state. In several notable
cases, high-resolution radio observa-
tions after such flares have directly
resolved radio- or even x-ray–emitting
blobs moving away from the central
black hole (16 , 17 ), which can be
kinematically traced back to the time
hard transition, although also sho
ing a range of luminosities at which
can occur (even in the same sourc
generally occurs at a luminosity o
few percent of the Eddington lum
nosity (24 ). In fact, the soft state h
never been convincingly observ
in any BHXRB at luminosities b
low 1% Eddington. By the time t
source reaches the canonical ha
state again, with almost exactly t
same spectral and timing charact
istics as the initial hard state, the
has reappeared, and the accreti
disc wind is gone. Once in the ha
state, the source decline continu
typically below the detection lev
of all-sky or regular x-ray monitorin
and are observed only occasiona
until their next outburst. These qu
phases are not without interest, ho
ever, for it is during these perio
that—without the glare of the brig
X-ray spectrum
X-ray luminosity
SOFT HARD
A
B
C
D
E
F
Black Holes
Fender & Belloni 2012 Science
X-ray luminosity
During this phase, the behavior of
the jet, revealed by infrared and radio
observations, also begins to change.
hard transition, although also show-
ing a range of luminosities at which it
can occur (even in the same source),
X-ray spectrum
SOFT HARD
B
C
Black Holes
soft X-ray spectrum hard
During this phase, the behavior of
the jet, revealed by infrared and radio
observations, also begins to change.
The infrared emission drops almost
as soon as the state transition begins
(14 ), indicating a change in the jet
properties(density andmagneticfield)
close to the black hole.
The radio emission begins to vary
more dramatically, showing oscilla-
tions and flare events superposed on
an overall decline (8 , 15 ). At a cer-
tain point, there are one or more large
radio flares, which can be two or more
orders of magnitude more luminous
than the previous existing, steadier jet
in the hard state. In several notable
cases, high-resolution radio observa-
tions after such flares have directly
resolved radio- or even x-ray–emitting
blobs moving away from the central
black hole (16 , 17 ), which can be
kinematically traced back to the time
of the state transition. It has been re-
cently shown that in some cases, the
ejection is coincident in time with the
appearance of the strong QPOs (15 ).
The soft state (D → E). As the
spectral transition continues, these
strong QPOs disappear, and the over-
all level of x-ray variability drops as
hard transition, althou
ing a range of luminos
can occur (even in the
generally occurs at a
few percent of the E
nosity (24 ). In fact, th
never been convinci
in any BHXRB at lu
low 1% Eddington. B
source reaches the c
state again, with alm
same spectral and tim
istics as the initial ha
has reappeared, and
disc wind is gone. O
state, the source dec
typically below the d
of all-sky or regular x-
and are observed on
until their next outbur
phases are not withou
ever, for it is during
that—without the gla
accretion disc—resea
to accurately measure
tions of the compan
optical telescopes an
mate the mass of the
self (25 , 26 ).
These cycles of
clear changes in the w
X-ray spectrum
X-ray luminosity
SOFT HARD
A
B
C
D
E
F
Black Holes
GRS 1915+105
low/hard XRB
low-luminosity
AGNs, Sgr A*
N+06; N+14
rsnemmen
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