Stability of CModes on Accretion Disks Around Black Holes
Giovanni Sáenz A., Manuel Ortega R. PhD.
School of Physics, UCR.
Nicolas Figueroa H., Abraham Madrigal R.
School of Electrical Engineering, UCR.
26 de Noviembre del 2004
Abstract
We compute numerically the sign and value of the viscosityinduced damping rate of fundamental c, or corrugation, mode oscillations in the inner part of accretion disks around black holes. The damping of these oscillations has been studied analytically by Ortega–Rodriguez & Wagoner (2000), who obtained orderofmagnitude estimates. However, their work did not determine the sign of the damping rate for the cmodes. We start from their results and calculate the damping rate for different values of the black hole´s angular momentum. Stability considerations might be important as these (or similar) modes could explain certain QPOs (quasi periodic oscillations) measured by the Rossi Xray Timing Explorer (see, e.g., Strohmayer).
Accretion Disk
Experimental Proof Rossi Xray Timing Explorer Strohmayer,T.E. 2001, ApJ, 554, L169 Wagoner, R.V. et al. 2001, ApJ, 559, L25
Accretion Disk Conditions Weakly viscous
r, z
Barotropic Newtonian Fluids Rotational, Stationary, Axial Symetry.
Geometrically thin,
optically thick.
dp 5 p d 3
Movement equations of a Newtonian Fluid t
t v a vb
ab
a
a
a v b
v
a b
v 0
b a
v
a
p
a
ab b
ab g 2
3
c v c
v a r a v r r a v z z a
r, z
d d
2.4 10 b 1 y 13
2
Silbergleit, A. S. & Wagoner, R.V. & OrtegaRodríguez, M. 2000, ApJ, 548, 335
3
2
y
z 1 h 2
OrtegaRodríguez, M. & Wagoner, R.V. 2000, ApJ, 537, 922 (Erratum 543,1060)
Effects of Viscosity Changes the unperturbed value of the fluid
variables characteristic in its equilibrium state.
Considerably changes the dynamic
description of the movement.
Eulerian Perturbation Assuming small viscosity terms (αρ*h*2Ω*, given
α<<1)
a v t
v v a
t
a
v v a
a
b
a
p a p b ab 2 2
v a
b
a
1
a v 0 a
a v a
a
b
a
2 3
vb
b
va
c c v
a
b
2 3
v
a b
c
vc
b a
v
Oscillation Modes P Modes (Inertialpressure): They are characterized by the restoration force of the
pressure gradients.
G Modes (Inertialgravity): Is characterized by a restoration force between
gravity and centrifugal forces.
C Modes (Corrugation): Vertically incompresible near de inner edge of the
disk.
Solution for the Eigenfrequencies 1
F1 F2 F3 F4 d F0 d 3 x
3
τ <0 >0
x
V0 2 2 F0 2 v0 S p r F1 2 2 2 F2 1 2
V0 z
2
V0 S r r
2
2
F3 2 S 2 2 2 2 S
r F4 S 1 p
Estable Crece Decrece
2 2 2 r z
V0 r
V0 r z
2
2
2
r r
3
2
a
1
r r 1
a: Black Hole´s Angular Momentum σ: Oscillation frequency on Earth.
4a r
3
2
2
3a 2 r
6 8a 3a r r 1 3 2 r r 2 r p
V0 r , y
S
2 3
2
Vr r Vy y
2
ω: Corrotation frequency. κ: Vertical radial epyciclic angular velocity.
2
r r
1
1
2
Ω: Rotation angular velocity. Ω⊥: Vertical epyciclic angular velocity.. δVr: Radial Amplitude. δVy: Vertical Amplitude.
2 1
Silbergleit, A. S. & Wagoner, R.V. & OrtegaRodríguez, M. 2000, ApJ, 548, 335
Magnitude order approximation m 1
S
2
z
1 1 ~ h*
F3 F4 d x h* 1 ~ 2 3 2 r 2 cs V0 d x 3
Silbergleit, A. S. & Wagoner, R.V. & OrtegaRodríguez, M. 2000, ApJ, 548, 335
2 z
~0
2
*
OrtegaRodríguez, M. & Wagoner, R.V. 2000, ApJ, 537, 922 (Erratum 543,1060)
Black Hole Types a
ri
σ
ro
105
5.99996734009787
7.799967340097872 4.3x108
104
5.99967339747862
6.479673397478621 7.4x107
103
5.99673362466632
6.146733624666323 8.6x106
102
5.96730105006149
6.020301050061486 9.1x105
101
5.66930257120862
5.686302571208621 1.1x103
0.5
4.23300252952703
4.238102529527025 0.011
a: Black Hole´s angular momentum. σ: Oscillation frequency on Earth. ri: Initial radius of the C Mode. ro: Final radius of the C Mode.
Silbergleit, A. S. & Wagoner, R.V. & OrtegaRodríguez, M. 2000, ApJ, 548, 335
Density and Pressure Definitions
0 1 y
2
3
p Vr r
e
0
2
2.4 106
cs
r rm
Vy y
l2
2y
Silbergleit, A. S. & Wagoner, R.V. & OrtegaRodríguez, M. 2000, ApJ, 548, 335
Results Damping Rate (τ) µ
b
1,E05
1,E04
1,E03
1,E02
1,E01
0,5
0
7,06E+06
2,60E+07
6,61E+06
4,62E+06
1,71E+06
1,31E+05
1
2,32E+06
1,47E+06
7,73E+05
6,25E+05
3,14E+05
4,08E+04
2
5,41E+05
2,52E+05
1,39E+05
1,14E+05
5,96E+04
8,44E+03
3
2,28E+05
1,01E+05
5,61E+04
4,60E+04
2,42E+04
3,46E+03
0
4,87E+06
7,94E+06
3,08E+06
2,30E+06
9,68E+05
9,03E+04
1
2,28E+06
1,56E+06
8,10E+05
6,51E+05
3,23E+05
4,14E+04
2
7,73E+05
3,84E+05
2,10E+05
1,72E+05
8,92E+04
1,26E+04
3
3,61E+05
1,66E+05
9,19E+04
7,53E+04
3,94E+04
5,63E+03
0
2,82E+06
3,03E+06
1,37E+06
1,06E+06
4,82E+05
5,22E+04
1
2,18E+06
1,84E+06
9,11E+05
7,23E+05
3,47E+05
4,27E+04
2
2,68E+09
1,78E+06
1,10E+06
9,35E+05
5,50E+05
9,25E+04
3
9,78E+05
3,35E+05
1,89E+05
1,56E+05
8,32E+04
1,20E+04
0
0,3
1
-4
|τ| vs µ (a = 10 ) 4.00E+06 1,00E+08
4.00E+04 1,00E+ 06
|τ|
4.00E+05 1,00E+07
1,00E+ 05 4.00E+03
1,00E+04 4.00E+02
1
2
3
4
µ 4.00E+01
b{0}
4.00E+00 Row 2
b{0.3}
b{1}
Row 3
Row 4
Column L
1 .0 0 E + 7
τ
1 .0 0 E + 6
1 .0 0 E + 5
a 1 .0 0 E + 4
1 .0 0 E + 3
µ 0
1
2
1 .0 0 E + 4
−τ
1 .0 0 E + 5
1 .0 0 E + 6
1 .0 0 E + 7
1 .0 0 E + 8 1 .0 0 E + 9
1 .0 0 E + 1 0
3
b
105
Negro
1
104
Azul
0.3
103
Verde
1
102
Amarillo
101
Rojo
0.5
Morado
1 .0 0 E + 7
τ
1 .0 0 E + 6
1 .0 0 E + 5
µ
a 1 .0 0 E + 4
1 .0 0 E + 3
b 0 .0 0
0 .2 0
0 .4 0
1 .0 0 E + 4
−τ
1 .0 0 E + 5
1 .0 0 E + 6
1 .0 0 E + 7
1 .0 0 E + 8 1 .0 0 E + 9
1 .0 0 E + 1 0
0 .6 0
0 .8 0
1 .0 0
105
Negro
1
104
Azul
2
103
Verde
3
102
Amarillo
4
101
Rojo
0.5
Morado
1 .0 0 E + 7
τ
1 .0 0 E + 6
1 .0 0 E + 5
µ 1 .0 0 E + 4
1 .0 0 E + 3
a 1 .0 0 E 6
1 .0 0 E 5
1 .0 0 E 4
1 .0 0 E 3
1 .0 0 E + 4
−τ
1 .0 0 E + 5
1 .0 0 E + 6
1 .0 0 E + 7
1 .0 0 E + 8 1 .0 0 E + 9
1 .0 0 E + 1 0
1 .0 0 E 2
1 .0 0 E 1
1 .0 0 E + 0
b
0
Café
0
1
Verde
0.3
3
Rosado
1
4
Naranja
Conclusions Generally, one can see that for most of the
combinations of a,b and µ, the value of τ is negative, then the C mode has a simliar behavior to the p and g modes where the viscosity effects cause an increase.
For all the ¨a¨ values the absolute value of
τ tends to decrease, but for the b=1 and µ =2 one can notice an increment.
The values for a decreasing T (positive)
are found when the volumetric part of the viscosity increases for values of the parameter of b=1.
For higher values of ¨b¨the slope of | τ | vs
µ tends to be lower, which means that the slope of the curve is inverse to the value of ¨b¨.
References
OrtegaRodríguez, M. & Wagoner, R.V.2000, ApJ, 537, 922 (Erratum 543,1060). Silbergleit, A. S. & Wagoner, R.V. & OrtegaRodríguez, M. 2000, ApJ, 548, 335 Strohmayer,T.E. 2001, ApJ, 554, L169. Wagoner, R.V. & Silbergleit, A. S. & OrtegaRodriguez, M. 2001, ApJ, 559,L25. OrtegaRodríguez, M. Ph.D. thesis, Physics Dept., Stanford Univ. Shapiro, S.L., & Teukosky, S.A. 1983, Black Hole, White Dwarfs, and Neutron Stars, The Physics of Compact Objects.
Regards To the Ministry of Science and Technology
(MICIT) and the National Council of Technology (CONICIT) in Costa Rica.
To the Research Vicerrectory of the
University of Costa Rica.