19/04/23 Variable Galactic Gamma-Ray Sources , Heidelberg, Germany 1

Maxim BarkovMPI-K, Heidelberg, Germany

Space Research Institute, Russia,University of Leeds, UK

Serguei KomissarovUniversity of Leeds, UK

Accretion/Blandford-Znajeck processes and jet formation

19/04/23 Variable Galactic Gamma-Ray Sources , Heidelberg, Germany 2

In the last few years we can see significant progress in general relativistic magneto hydrodynamics (GRMHD) simulations of BH accretion systems. It reveals a flow structure that can be decomposed into a disk, corona, disk wind and highly magnetized polar region that contains the jet (De Villiers, Hawley and Krolik 2003; Hawley and Krolik 2006; McKinney and Gammie 2004; McKinney 2005, 2006, 2007; McKinney and Balndford 2009; Shibata, Sekiguchi and Takahashi, 2007, Barkov and Komissarov 2008, 2010, Barkov and Baushev 2011).

Blandford-Znajek mechanism

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Setup

v

B

v

B

v

v

v

(Barkov & Komissarov 2008a,b)(Komissarov & Barkov 2009)black hole

M=3Msun a=0.9

Uniform magnetization R=4500km

= 4x1027-4x1028Gcm-2

outer boundary, R= 2.5x104 km

free fallaccretion

(Bethe 1990)

• 2D axisymmetric GRMHD;• Kerr-Schild metric;• Realistic EOS;• Neutrino cooling;• Starts at 1s from collapse onset. Lasts for < 1s

Rotation:

rc=6.3x103kml0 = 1017 cm2 s-1

230 1,/minsin crrll

III. Numerical simulations

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Free fall model of collapsing star (Bethe, 1990)

radial velocity:

mass density:

accretion rate:

Gravity: gravitational field of Black Hole only (Kerr metric); no self-gravity;Microphysics: neutrino cooling ; realistic equation of state, (HELM, Timmes & Swesty, 2000); dissociation of nuclei (Ardeljan et al., 2005); Ideal Relativistic MHD - no physical resistivity (only numerical);

1

2/11

1 1011.0

sM

M

M

s

tCM sun

sun

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magnetic field lines, and velocity vectors

unit length=4.5km t=0.24s

Model:AC1=9; Bp=3x1010 G

log10 (g/cm3) log10 P/Pmlog10 B/Bp

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magnetic field lines, and velocity vectors

unit length=4.5km t=0.31s

Model:AC1=9; Bp=3x1010 G

log10 (g/cm3)

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Model:AC1=9; Bp=3x1010 G

log10 (g/cm3)

magnetic field lines

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Model:CC1=3; Bp=1010 G

velocity vectors

log10 P/Pm

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Jets are powered mainly by the black hole via the Blandford-Znajek mechanism !!

• No explosion if a=0; • Jets originate from the black hole;• ~90% of total magnetic flux is accumulated by the black hole;• Energy flux in the ouflow ~ energy flux through the horizon (disk contribution < 10%);• Theoretical BZ power:

15122

227

50 1048.0106.3 sergMafEBZ

Model: C

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1/50 of case a=0.9

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GB

CsMM SUN

10

11

103

315.0

9.0

10 12170

a

scml

9.0

103 12170

a

scml

5.0

10 12170

a

scml

0.0

10 12170

a

scml

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)(log10

m

g

PP

10log

GB

CsMM SUN

10

11

103.0

315.0

9.0

10 12170

a

scml

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Different magnetic field topologies:Dipole, quadruple 1 and quadruple 2.

The initial conditions consist of an equilibrium torus (Fishbone and Moncrief 976; Abramowicz et al. 1978; Komissarov 2006), which is a "torus" of plasma with a black hole at the center. The value of the specific angular momentum of matter and angular momentum of BH ‘a’ determines the total effective potential.

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Magnetic flux Ψ time evolution

iidsB

Time evolution of magnetic flux of model Quadruple 2 on horizon, t=0.00496 sec -- solid,t=0.0248 sec -- dashed, t=0.1238 sec -- doted, t=0.4452 sec -- three dots dashed.

Time evolution of magnetic flux of Dipole model on radius r=4.7 rg left panel and on horizon central panel, t=0.00496 sec -- solid,t=0.0248 sec -- dashed, t=0.0495 sec -- dot dashed, t=0.0991 sec -- doted, t=0.346 sec -- three dots dashed.

2

46

1

h

BZ cE

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Dipole Quadruple 1

Quadruple 2

Radial component of magnetic field.

4/1

1610)(

G

BBsign rr

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Quadruple 2. Radial component of magnetic field.

4/1

1610)(

G

BBsign rr

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a=0 a=0.9

Flux of matter (MA) - bottom panels and electromagnetic (EM) - up panels per radian depends on θ and time on radius R=180 rg.

In our simulations up to ½ of initial electromagnetic flux are transformed to non-relativistic hot wind though numerous shock waves.

It can supply hot corona in such objects as SS433.

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Lorentz factor

• Distribution of Lorentz factor and magnetic lines for time 0.2075 sec.

• Cooling case provides most stable and powerful outflow.

• The Lorentz factor achieves Γ≤ 4.5 (numerical restriction)

Modified coolingNo cooling Cooling