“HR-diagram” for BHs: stellar BHs change states
in Δt ~ days; AGNs in Δt ≳105 years?
phase, the behavior of
by infrared and radio
so begins to change.
mission drops almost
tate transition begins
a change in the jet
ty andmagneticfield)
ck hole.
mission begins to vary
lly, showing oscilla-
vents superposed on
ne (8, 15). At a cer-
are one or more large
h can be two or more
tude more luminous
s existing, steadier jet
e. In several notable
lution radio observa-
flares have directly
r even x-ray–emitting
way from the central
17), which can be
ced back to the time
hard transition
ing a range of
can occur (eve
generally occu
few percent o
nosity (24). In
never been co
in any BHXR
low 1% Eddin
source reache
state again, w
same spectral
istics as the in
has reappeare
disc wind is g
state, the sou
typically belo
of all-sky or re
and are obser
until their next
phases are not
ever, for it is
that—without
X-ray spectrum
X-ray luminosity
SOFT HARD
A
B
C
D
E
F
oles
Fender & Belloni 12 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
ing a range of luminosities at w
can occur (even in the same s
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
X-ray spectrum
X-ray luminosity
SOFT HARD
A
B
C
D
E
F
Black Holes
low/hard XRB
low-luminosity
AGNs, Sgr A*
N+06; N+14
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