Transcript Document

Thermal balance of the jet in the
microquasar SS433
G.S. Bianovatyi-Kogan, Yu.N. Krivosheev
Space Research Institute, Moscow (IKI RAN)
HEPRO-III, Barcelona
28 June, 2011
SS433 is a unique massive X-ray binary system with precessing
relativistic jets. It is situated at a distance of approximately 5 kpc = 1.5 10^22 cm
nearly in the galactic plane. The optical companion V1343 Aquilae was first
identified in the survey of stars exhibiting H_alpha (656 nm) emission by
Stephenson and Sanduleak in 1977.
This binary has been observed in radio, optical, ultraviolet and X-ray for
three decades, and nevertheless there are several puzzles concerning this object
that remain to be solved, for instance, the nature of the relativistic object and the
mechanism of collimation and acceleration of matter in jets to relativistic velocity.
orbital period of binary system
1. The origin of the broadband X-ray spectrum of
SS433 from 3 to 100
keV
2. Getting the values of
some physical
parameters of the
source
3. Thermal balance of the
jet
SS433
•
It is almost certain that there is a black hole in SS433 system.
•
This binary system consists of an optical star and a black hole, surrounded
by an accretion disk with a couple of jets. Mass ratio of SS433 components is
q  M X / MV  0.2  0.3
•
object
One of SS433 pecularities is supercritical regime of accretion onto relativistic
4
( M ~ 10 M sun / yr, M cr~ 107 M sun / yr ( M X  10M sun )
)
•
Powerful jets of conical shape have kinetic luminosity about Lk ~ 1039 40 erg / s ,
the velocity of matter in jets is almost one third of light speed (0.26с)
Fabrika S.,2004 ,ApSS Reviews, 12, 1
 jet  1.20
Binary separation
a  4 1012 cm
rjet  1013 cm
rdisk  1.5 1012 cm
 disk  40
M bh  7  M Sun
q
M bh
 0.3
M opt
-2
-3
10
2
lg I, phot/cm /sec/keV
In this figure the SS433 spectrum
in the range from 3 to 90 keV is
presented. It was obtained from
INTEGRAL data (JEM-X points
from 3 to 20 keV and IBIS (ISGRI)
points from 20 to 90 keV). The
spectum corresponds to
precessional moment T3, i.e.
when the angle between jet axis
and the line of sight is equal 60
degrees and the disk is maximally
‘face-on’.
10
-4
10
-5
10
10
100
lg h, keV
Cherepashchuk A.M.,Sunyaev R.A., Fabrika S.N., Postnov K.A. et al., 2005, A&A, 437, 561
Cherepashchuk A.M.,Sunyaev R.A. et al., 2006, Proceeding of 6th INTEGRAL Workshop, Moscow,
Russia
Monte-Carlo simulations of the X-ray spectrum
of SS433
Yu. M. Krivosheyev, G. S. Bisnovatyi-Kogan,
A. M. Cherepashchuk and K. A. Postnov
MNRAS, 394, 1674–1684 (2009)
It follows from observations, that jet’s opening angle in X-ray range is
about 1.2 degrees. That leads us to the assumption that jet is of conical shape.
 r0 
T

T
Temperature profile: jet
cor 

r
4
3
1,0
F(r/r0)
0,8
v0
corresponds to adiabatic cooling of
expanding ideal gas.
Density profile:
 r0 
n  n0  
r
Follows from the equation of
continuity with the following
expression for n0:
0,6
2
0,4
0,2
0,0
2
4
M is mass loss rate in the jet
n0 
M
m p v0 r0 2 
v0  0.26c is the radial velocity in the jet
 is the solid angle, occupied by the jet
6
8
10
r/r0
r0 , the outer one is rcor .
•
The corona has a spherical shape, its inner radius is
•
It was considered to be isothermal, with temperature equal to Tcor  20keV.
•
The density profile was taken to be the same as in the jet for simplicity, but
with different value at r0.
 cor   T
rcor

r0

r0 
n(r )dr  T n0 r0 1  
 rcor 
And thus we can obtain the formula
for the outer radius of the corona:
rcor
- optical depth of corona with
respect to Thomson scattering
r0

1   cor /  T n0 r0
•
It was assumed that the size of the accretion disk coincides with that of
12
Roche lobe and is equal rdisk  1.5 10 cm .
•
One can find the half thickness of the disk using the standard disk accretion
theory in the gas-dominated region with free-free opacity, which begins from the
10
radius rbc  4·10 cm (Shakura&Syunyaev, 1973, A&A, 24, 337-355) and then,

assuming linear growth of thickness with radius h  r tan disk , obtain the disk’s half2
opening angle. It is equal 2 degrees (approximately).

3 1/10  M
h  6.1·10 
 M˙
 cr




3/20
 M 


M
 Sun 
9/10
 R

 3Rg



9/8
  R
1  
  3Rg




1/2 3/20




Geometry of
the
computational
domain
V jet  0.26c
rcor
r0  1011 cm
Angle dependence of SS433 spectrum
-2
10
-3
10
2
I, phot/cm /sec/keV
In the figure the spectra of
the source for three angles
of observation is shown: 60
degrees (solid line), 82
degrees (dotted line) and 90
degrees (dash-dotted line).
In the last case the
contribution of both
hemispheres was taken into
account, in the first two
cases it wasn’t necessary.
-4
10
-5
10
10
100
h, keV
The observed X-ray flux is small at 90 degrees, so the second hemisphere is
not visible, and outer parts of the disk have larger thickness, that SS model.
The observational points correspond to the angle ~60 degrees.
Heating mechanisms of the jet in
SS433
B.-K., K. Astron. Zh. (in press)
Sources of heating
1. Compton effect of hard X rays from corona on jet
electrons
2. Heating due to dissipation of the energy of shock waves
moving along the jet, and generated near the origin
3. Heating due to transformation of the jet kinetic energy
into the heat in the collisions of the corona and jet
protons.
Equation of a thermal balance of the jet
Density profile
Radiative energy losses
Solution of the equation of the energy balance in jet
Temperature profiles of the jet temperature with account of
adiabatic expansion only (hard curve), and with account of
radiative energy losses (dotted curve).
Radiative losses curve due to free-free (dotted curve), and
with account of free-bound, and bound-bound losses
Account of Compton heating
Energy density of photons
Integrating over the frequency::
Input into the thermal balance
Jet heating due to dissipation of shock waves
Hugonit adiabate
This expression is used in the equation of the balance of the
internal energy, together with radiative losses. The value
Delta (t) is established from the observations of the X ray
variability of SS 433, on the time scale ~ 1 second.
To close the system, we derive the equation, determining the
change of the energy flux in the shock, propagating along the
jet..
The density of the flux of the energy of the shock wave, equal
to the energy moving through the unit of square in a unit time
$D$ is the a velocity of the shock relative to the jet
The system describing the thermal balance of the jet with shocks
Jet temperature
profile with account
of shock wave
heating
Shocks heat only a small region of the jet,
around the place of the shock origin.
The whole jet could be heated only by a
system of shocks formed along the jet, and
dissipating at different lengths.
May be the “clumpy” structure of jets is
connected with a shock heating.
Coulomb collisions of protons
Thermal protons from corona enter the jet, becoming
targets, on which jet protons, moving with a speed 0.27 c
are scattered. Jet protons loose their kinetic energy due
to scattering. The kinetic energy of jet is transformed
into heat.
Estimate a maximal heating rate by this mechanism, when
the proton entering the jet is thermolised inside the
jet, transforming into the heat the energy (М_р vjet^2/2)
(erg/g/sec)
The mean free path of the proton due to Coulomb collisions is much less than the
jet radius, therefore the heating by collisions is much less than the maximally
possible. On the corona radius
Magnetic field influence
Jet temperature
profile
with radiative
losses and
collisional
heating at a=const
1.0, 0.5, 0.3, 0
Same for
variable
a
Heating of the optical jet in SS 433
Optical jet:
r ~10^14-15 cm (10^3-4 r0),
almost constant temperature T ~ 10^4 Ê.
Heating is necessary to balance radiative and adiabatic losses
Heating by collisions with the protons of corona and stellar
wind
T_0 = 2.2 10^8 K until r = r_cor = 6. 4 10^11 cm,
Adiabatic law at larger radius
T ~ rho^{2/3}~r^{-4/3}.
Temperature
profile of the jet:
Solid line –
best fit by
analytic formula
Dotted line – pure
adiabatic profile
Dashed line –
simpler for heating
1.
SS433 spectrum in the region form 3 to 90 keV origins from
comptonized free-free emission of corona and jet (with the exception of
small region near 7 keV, where line formation is important)
2.
Еmission from accretion disk plays an important role in spectrum
formation for lower energies and makes no contribution to the source’s
spectrum in the range considered.
3. Most effective heating mechanism of the jet in SS 433 is
connected with kinetic energy losses by collisions with
surrounding matter (protons), in presence of a very moderate
magnetic field. Collisions may support T~10^4 Ê in the
optical jet. Shocks distributed over the jet may give an
input into heating.
4. The losses of the kinetic energy are relatively very small ~10^{-4}, and the
velocity change along the jet is hardly observable..