Astrophysics and Space Dynamics Department Space and Solar - Terrestrial Research Institute

Astrophysics and Space Astrophysics and Space Dynamics DepartmentDynamics Department

Space and Solar - Terrestrial Research Institute

Astrophysics and Space Dynamics Astrophysics and Space Dynamics ©©

Research topicsResearch topics

Dynamics and Evolution of accretion discs;

Synergetic;

Physics of Shocks in Astrophysical objects;


Dynamics and evolution of accretion discDynamics and evolution of accretion disc

Credit for animations: Dana Berry, NASAhttp://www.nasa.gov/centers/goddard/news/topstory/2003/0702pulsarspeed.html


Dynamics and evolution of accretion discDynamics and evolution of accretion discMethods and mechanisms of researchMethods and mechanisms of research

• Results of magneto-hydrodynamical approximation

It isIt is investigate investigatedd the basic equations of magneto- the basic equations of magneto-hydrodynamics for non-stationary and non-axihydrodynamics for non-stationary and non-axi--symmetrical symmetrical accretion flowsaccretion flows..

It is obtained global It is obtained global solutionsolutionss for for the the 2D 2D andand 3D 3D structurestructuress and theand the evolution evolution ofof accretionaccretion diskdisk. .


T h i s i s t h e d i s t r i b u t i o n o f d i m e n s i o n l e s s d e n s i t y f 1 ( X ,Y ) i n n o n -a x i s - s y m m e t r i c M H D m o d e l .

WW ee cc aa nn ss ee ee oo nn ff ii gg uu rr ee tt hh ee bb ee gg ii nn nn ii nn gg oo ff tt hh ee ss pp ii rr aa ll aa bb oo uu tt tt hh ee oo uu tt ee rr ee dd gg ee aa ss ll ee aa pp ii nn ff uu nn cc tt ii oo nn oo ff tt hh ee dd ee nn ss ii tt yy oo nn 00 .. 99 хх ..

T h i s i s t h e d i s t r i b u t i o n o f t h e d i m e n s i o n l e s s r a d i a l v e l o c i t y f 2 ( X ,Y ) . WW ee ss ee ee tt hh aa tt tt hh ee tt ww oo tt ww ii gg ss aa rr ee ss ee pp aa rr aa tt ee ii nn tt hh ee ee nn tt ii rr ee dd ii ss cc .. TT hh ee rr ee aa rr ee ss ii mm uu ll tt aa nn ee oo uu ss ii nn cc rr ee aa ss ee aa nn dd dd oo ww nn ff aa ll ll oo ff rr aa dd ii aa ll vv ee ll oo cc ii tt yy ff oo rr ff ii xx aa nn gg uu ll aa rr cc oo --oo rr dd ii nn aa tt ee == >> tt hh ee ff ll uu ii dd pp aa ss ss ii nn ii nn dd ee pp ee nn dd ee nn tt ii nn tt hh ee bb oo tt hh dd ii rr ee cc tt ii oo nn ss ..

SS uu cc hh bb ee hh aa vv ii oo rr oo ff tt hh ee vv ee ll oo cc ii tt yy ss hh oo ww ss aa vv aa ii ll aa bb ii ll ii tt yy oo ff mm ii cc rr oo -- vv oo rr tt ii cc ee ss ii nn aa ll ll

tt hh ee dd ii ss cc ..

0 0 . 5 1 0 . 5

1 . 5

2 . 5

- 1

X 0

- 1 0

1 Y

0

1 e + 0 9

- 1 0

X

0 - 1

0

1 Y

1 e + 0 8

T h i s i s t h e d i s t r i b u t i o n o f d i m e n s i o n l e s s o f d e n s i t y f 1 ( x , Z ) f o r t h e p o i n t o f s p r e a d i n g ( φ 0 = 0 ) i n m o m e n t . t = 1 P ~ Ω 0

- 1 .

P r o f i l e ( x , Z ) f o r f 1 ( x , Z ) = 1 0 6 ; 1 0 8 ; 1 0 1 0 .

T h i s i s t h e d i s t r i b u t i o n o f d i m e n s i o n l e s s d e n s i t y f 1 ( x , Z ) f o r t h e p o i n t o f s p r e a d i n g ( φ 0 = 0 ) i n m o m e n t t = 0 .

P r o f i l e ( x , Z ) f o r f 1 ( x , Z ) = 1 0 6 ; 1 0 8 ; 1 0 1 0 .

0

x Z 1

0

0 . 0 8

1 e + 0 8

0

1

x

0

0 . 0 8

Z

1 e + 0 8

7 e + 0 7 7 . 5 e + 0 7 8 e + 0 7 8 . 5 e + 0 7 9 e + 0 7 9 . 5 e + 0 7

0 x 1

0

Z

0 . 0 8

0 1 x

0

0 . 0 8

Z



In 3D for planes Z=const and x= const we can get the distribution of level for the chosen coordinate.

For contours 108 and 1010 on the density for t ≈ 0 we observe maximums and this mark for t ≈ 0, spreading is

going on. The solution in moment t ≈ 0Ω0-1, in the form f1(x)exp(-

ω0f7(x)/Ω0) along the whole disc, because coefficient ω(r) is indefinitely and the coefficient kφ(r) is zero. After the instantly spreading of the disk, there are not instabilites, yet.

In the results of 2D-structure of the disc are appear short-live formation-rings with enhanced density.

We are building a model of such a formation and obtaining local heating and getting the local dependences of instabilities from warming: ω(K) and kφ(K), and kr(K) of an orbit r.

We investigate local condition va < vs, on different levels for different radius in disk and discuss results in terms of magneto-rotation instability existing, their connection with generating of the corona like consequences.

We use the potentialities on the developed model, to concrete objects, representatives of BH with different masses. Aim to do results comfortably for comparative analyses.

Modifying is the disk model for conditions in disk’s corona. Aim to do possible to put stitches the solution for corona with solution in disk, when the two global flows have no total energetics.



D e v e lo p m e n t o f th e c o n d it io n o n х fo r (0 .0 7 5 ; 0 .0 8 ) Z .

D e v e lo p m e n t o f th e c o n d itio n o n х fo r (0 .0 5 5 ; 0 .0 6 )Z .

D e v e lo p m e n t o f th e c o n d it io n o n х fo r (0 .0 3 5 ; 0 .0 4 ) Z .

D e v e lo p m e n t o f th e c o n d itio n o n х fo r (0 .0 0 1 ; 0 .0 0 2 )Z .

|v a |< |v s |

|v a |< |v s | |v a |> |v s |

|v a |> |v s | |v a |< |v s |

|v a |> |v s | |v a |< |v s |

0 1 x 0

1 0 0 0

0 1 x 0

1 0 0 0

0 1 x 0

1 0 0 0 0

0 1 x 0

1 e + 1 0

|v a |> |v s |

D evelopm ent o f the cond ition on Z fo r 1 .0х .

D evelopm ent o f the cond ition on Z fo r 0 .6х .

D evelopm ent o f the cond ition on Z fo r 0 .1х . Then |v a|< |v s| on ly for Z< 0.002 .

0 .08 Z 0

1e+ 07

|v a |> |v s|

|v a |< |v s|

0 .08 Z 0

1000

|v a |< |v s| |v a |> |v s|

0 .08 Z 0

1000




• Results of hydrodynamical approximation

In nonlinear study it is needed to apply numerical methods:Runge-Kutta numerical method, combined with computational software, gives the next graphical results:

Two images show the variations of density /left/ and the velocity values drops-off /right/ in the flow.



• Results of numerical simulation of vortices formation.

Further development of the baroclinic instability turns it into the source of vorticity formations in the discs. Applying numerical code, and after performing a series of runs, it is presented the simulation of this kind of pattern growth in plane of the disc zone.



• Observational effects of unstable behavior

Observationally, the outbursts and pulsations of Cataclysmic Variables are expressed in their light curves and revealed by exchanges in luminosities.

Light curve of CV GK Per /Perseus/ (RK catalogue of X-ray stars). It is observed the X-Ray pulsations with rapid than slow irregular variations in the luminosity. The image is created on the observational data of AAVSO /www.aavso.org/.



• Applying of bifurcation analysis

a bifurcation is any qualitative or topology reconstruction of the system, when the parameter of the system crosses its critical value. When a given system passes through a bifurcation point, it may lose its stability. It is seen in the figure this transition trough the critical point.

-80-60

-40-20

020

4060

80

lambda(c)

-40-20

020

4060

80100

120

w(c)

-4

-2

0

2

4Psi(r)

The bifurcation theory is a powerful tool for analyzing the nonlinear evolution of instability behavior in pattern forming systems.


Synergetics Synergetics Subjects and methods of researchSubjects and methods of research

Study of the Driving forces- stabilization and disruptive modes; Systems’ Evolution Hierarchies- their Transitional Stages and Time scales; Time- "periodicity"- paradoxes in the structure of an astrophysical system’s activity; The trigger effects from: Interstellar dust properties, giant planets’ & sudden energy release (GRB) influence on: IPM, magnetic field generation & planetary atmospheres; A Study of Possible Scenarios as a Result of Rapid and/or Burst-like, Long-term;


Physics of Shocks in Astrophysical

objects ResearchResearch Projects and resultsProjects and results

In general, this topic may include a broad variety of objects but the basic interests here are related to shocks in stellar winds, their interaction with the interstellar matter, supernova remnants. Since the gas flows in the studied objects are highly supersonic, the postshock temperatures are of the order of a million Kelvin and even much higher, therefore, the primary shock emission is in X-rays. All the observations that are part of this science project are done with the modern X-ray observatories Chandra (NASA) and XMM-Newton (ESA), as the three basic subprojects are as the following.




• Monitoring the birth of the supernova remnant in the Large Magelanic Cloud (SNR 1987A)

A new phenomenological model is being developed that is capable of explaining the observed X-ray emission and how it is related to the shock emission in other spectral domains.

The observations are done as part of numerous projects with the Chandra X-ray observatory (PI: Prof. D. Burrows, The Pennsylvania State University, USA for the imaging in 2000 - 2009; PI: Prof. R. McCray, University of Colorado at Boulder, USA for the spectral observations in 2004-2007) The figure is published in S. Zhekov et al. (2004, Astrophysical Journal, 628, L127-L130).


• Colliding stellar winds in massive binaries



WR+O binaries are one of the brightest X-ray sources amongst the massive stars. Their enhanced emission originates from the interaction region of the winds of the two massive stars. A phenomenon called colliding stellar winds(CSW) being an ideal laboratory for studying the shock physics.

A new CSW model (see Figure 3) was used to analyse the X-ray spectrum of the massive binary system WR 147 that was obtained with the XMM-Newton X-ray observatory (PI: Dr. S. Skinner, University of Colorado at Boulder, USA). The figure is from S. Zhekov (2007, MNRAS, 382, 886-894).




• X-ray emission from single massive stars

It was used for analysis of a sample of 15 massive OB stars. The data were taken from the archive of the Chandra observatory. X-ray spectra of presumably single WR stars were analysed over the years. These projects are based on data taken with Chandra and XMM-Newton X-ray telescopes (PI: PI: Dr. S.Skinner,University of Colorado at Boulder, USA).

The present concept on theorigin of X-rays in massive stars (OB and Wolf-Rayet) posits that they are emitted by hot gas heated by shocks. OB and WR stars possessmassive and fast winds driven by radiation pressure and subject to instabilities (radiation-driven instabilities) which may give rise to the formation of strong shocks.


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Astrophysics and Space Dynamics Department Space and Solar - Terrestrial Research Institute