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Gamow conference, Odessa , 2 0.08. 20 0 9. Ivan L. Andronov Odessa National Maritime University. Space Laboratory to Study Accretion in Magnetic Cataclysmic Variables: The Case of Exotic Newly-Discovered Polar OTJ 071126+440405.

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slide1

Gamow conference, Odessa, 20.08.2009

Ivan L. Andronov

Odessa National Maritime University

Space Laboratory to Study

Accretion in Magnetic Cataclysmic Variables:

The Case of Exotic Newly-Discovered Polar

OTJ 071126+440405

international collaboration
International collaboration
  • Inter-Longitude Astronomy (ILA):
  • Polar – photopolarimetric and spectroscopic study of gravimagnetic rotators in cataclysmic variables (in Ukraine, using the CrAO telescopes)‏
  • Superhump – study of the precession of accretion disks in nova-like and dwarf nova stars
  • Stellar Bell – analysis of multi-component pulsations of short- and long- period variable stars based on own photometric observations and the data from the international databases of UAVSO (Ukraine), AFOEV (France) and VSOLJ (Japan).
  • SCJ - Star classification and justification of suspected variables from surveys (space observatories: Hipparcos-Tycho and ground-based: Sky Patrol).
general classification of non magnetic and magnetic binary stars
General classificationof non-magnetic and magnetic binary stars
  • non-magnetic cataclysmic binary stars (ex-Nova, dwarf Nova, Nova-like)
  • “semi-magnetic” cataclysmic binary stars (intermediate polars)
  • magnetic cataclysmic binary stars (synchronizing polars)
  • magnetic cataclysmic binary stars (classical polars)
slide5

General modeldepends on characteristic dimensions:Rwd – radius of the white dwarfRA-Alfven Radius (magnetosphere)Rc- co-rotation radiusRd- maximum dimension of diskRL– distance to the inner Lagrangian pointa – orbital separation

  • Always: Rwd<Rd<RL< a, but

Rwd ~RA-”non-magnetic”

Rwd <RA~Rc <~Rd intermediate polars

Rwd <Rc < RA~ Rd<RL

asynchronous polars

Rwd <Rd < Rc = RA~RL

classical polars

types of variability
Types of Variability:

Non-Magnetic

Magnetic (polars)

Characteristic timescale

Nova-like

classical

Dwarf Novae

asynchr

IP

theoretical models of magnetic binary stars
Theoretical modelsof magnetic binary stars
  • “Asymmetric propeller" – synchronization of the spin and orbital periods of the white dwarf owed to ejection of plasma by magnetic field (additional centrifugal force)
theoretical models asymmetric propeller ejection
Theoretical models: “Asymmetric propeller" –ejection
  • Gravitation
  • Coriolis force
  • Centrifugal force
  • Viscosity
  • Gas pressure
  • Magnetic channeling
theoretical models of magnetic binary stars1
Theoretical modelsof magnetic binary stars

“Standard model" – accretion flow channelized by the magnetic field:

“Magnetic valve” (dependence on the accretion flux and torque on the orientation of the magnetic axis

slide12
Ivan L. Andronov,

Odessa National Maritime University;

Alexey V.Baklanov,

Crimean Astrophysical Observatory

Vadim N. Burwitz

Max-Planck Institut fuer Extraterrestische Physik (Germany);

Observatori Astronomic de Mallorca (Spain)

A & A 2006

The unique magnetic cataclysmic system

V1432 Aql:

Third type of Minima,

Synchronization and

Capture Radius

var comp instrumental vr magnitudes choosing an optimal local constant linear fit
“Var-Comp” instrumental VR magnitudes choosing an optimal local constant/linear fit

HJDmin = 2451492.11112(14) + 0,140235812(12) × (Е –16347).

var comp instrumental vr magnitudes the orbital dip was removed
“Var-Comp” instrumental VR magnitudes The orbital “dip” was removed

spin wide 1

spin narrow 2

HJDspin = 2453223.8359(13)+ 0.140585(30) *Е (2004г.)

three types of minima
Three types of minima

spin wide 1

1 orbital period

2 spin period

migrating minima

beat period ~60 days

spin narrow 2

orbital "dips"

|

Andronov, Baklanov & Burwitz (2005)

4 subsequent nights from 18

synchronization of the white dwarf acceleration of the slow spin rotation
Synchronization of the white dwarf (acceleration of the “slow” spin rotation):
  • HJDspin= 2449638.327427(74) + 0.14062831(23) *Е -7.81(11) 10-10 *Е2 (1993-2004)
  • HJDspin = 2453223.8359(13)+ 0.140585(30) *Е(2004)
period variations
Period variations:
  • TE= T0+P*Е +Q* Е2
  • dP/dt=2Q/P, (dP/dt)/P=2Q/P2
  • Q=-9.14.10-10 (Staubert et al. 2003 , 1.5s)
  • Q=-6.5.10-10 (Mukai et al. 2003, 9s)
  • Q=-7.81(11) . 10-10(all data:1993-2004 , 61s)

Theory: AM Her (similar parameters) : 6<t<260 yrs (Andronov 1982)

Observations: BY Cam (Silber et al. (1997), Mason et al. [1998]),

V1500 Cyg (Pavlenko and Pelt (1988), Pavlenko and Shugarov 2005)

slide18

Distances from the center of the white dwarf to:a – center of the secondaryRL – inner Lagrangian pointRY – Roche lobe in the orbital plane (“Y”)RHS – “hot spot” (Warner & Peters 1972)16RWD – minimal capture radius RWD – surface of the white dwarf

+

Andronov & Baklanov (Af 2007)

slide19

Two limiting models of the accretion columns :1 - “vertical” (or height << radius) 2 - “inclined” (or height >> radius) (hope that the truth is somewhere in between):

Δφ

R0/ RWD (model 1)

R0/ RWD (model 2)

0.42

36

16

0.43

47

21

0.44

64

28

φ+ ψ(φ)= π(1-2Δφ)/2

dipole

magnetic

field

line

white

dwarf

1s "corridor" of Df

model 1

model 2

results briefly
Results (briefly):

Most precise:

Orbital period

Spin period

Spin period variations + synchronization time

Beat period of 57.201d

First (observations):

3-rd type of minima

2-color (VR) photometry -> color index -> temperature

First (theory):

Capture radius range from the phase difference

Self-consistent values of the parameters:

Distance

Accretion rate

Capture radius

Mass/Radius of the white dwarf

slide21
Very new object: OTJ 0704

Discovered on December 31, 2008/January 1, 2009

Short orbital period (117 minutes)

Deep eclipse (7minutes, from ~15 to ~19 magnitude)

Pre-eclipse: 17 minutes before

Out-of the outburst asymmetric wave

Mean brightness variations: ~15 in January, ~18 in February, Maximum at the beginning of March

Drastic color variations ~0.6 mag!!!

Observations at 1-m Korean telescope at Mt.Lemmon (USA)

March 11-19, 2009 (Yoh-Na Joon (became a father during obs))

1-m (Slovakia), 2.6m, 1.25m (Ukraine)

slide22

Crimean Astrophysical Observatory: AZT-11

S.V.Kolesnikov (reduced with MUNIpack by V.V.Breus):

Faint minima missing

reduced with WinFits by L.L.Chinarova:

Measuring all

slide27

Crimean Astrophysical Observatory:

ZTSh (1 sec) – S.V.Kolesnikov, N.M.Shakhovskoy

Reduced with ZTShServer (V.V.Breus)

Wide R filter (intensities “var/comp”)

slide28

These studies of the magnetic cataclysmic variables were initiated in 1978 by

Prof. Vladimir P.Tsessevich

(1907-1983)

when I was a 3-rd year student and was interested in mathematical modeling of unstable Universe, black holes, gravitational lenses and pulsations

slide30

Arto Oksanen (Finland) :

3 unexpectedly different luminosity states

theoretical models of magnetic binary stars2
Theoretical modelsof magnetic binary stars
  • 2D - oscillations of the orientation of the magnetic axis

Red dwarf

White dwarf

theoretical models of magnetic binary stars3
Theoretical modelsof magnetic binary stars
  • 3D - oscillations of the orientation of the magnetic axis
theoretical models of magnetic binary stars4
Theoretical modelsof magnetic binary stars
  • “Swinging dipole" – excitation of the auto-oscillations of the orientation of the magnetic axis with characteristic time of~1-10years
model of dipole thin disk dependence of the equilibrium period on the orientation andronov 2005
Model of Dipole+thin disk:Dependence of the equilibrium period on the orientation (Andronov 2005)
slide35
Spin phase variabilityas function of the orbital phase+correlated irregular shifts:clues for determination of the column orientation

Kim, Andronov et al. (2005)

slide36
Angular characteristics of the Roche lobe (Andronov, 1992)

Improved expressions presented

In the poster: Andronov & Breus, this conf.

slide37

Dependence of the eclipse duration (in degrees) on the orbital inclination

for various values of the mass of the white dwarf

slide39

The model of the system computed assuming the mass ratio q=0.3. The red dwarf (RD) fills its Roche lobe (RL). The plasma moves from the inner Lagrangian point (LP) initially along the ballistic (collisionless) trajectory (BT) and then captured by the magnetic field of the white dwarf (WD) and then moves along the dipole line (DL). At the low state, the thread point is close to the Lagrangian point, so the self-eclipse (SE) of the accretion column is observed closer in phase to the main eclipse of the main emission region by the red dwarf (when the line of centers (LC) is closest to the line of sight). The self-eclipse at the high state (SEH) is observed at another phase, practically corresponding to the minimal angle between the line of sight an the magnetic axis.

monitoring of selected cataclysmic variables am herculis
Monitoring of selected cataclysmic variables – AM Herculis
  • Statistical dependence of the phase curve and characteristics of flickering on luminosity …
  • Changes of orientation of the accretion column (I.e. magnetic axis of the white dwarf) have been confirmed, which had been predicted by the “Swinging Dipole” model.
  • Unprecedented flare of the red dwarf of the UV Ceti -type
  • Minute-scale variability as the “Red noise”.
  • Fractal behaviour of luminosity variations in unprecedentally wide range from seconds to decades
theoretical models of magnetic binary stars5
Theoretical modelsof magnetic binary stars
  • Advanced models of the “Standard” accretion column :
  • Non-homegeneous
  • Asymmetric
  • Inclined
  • “Rainbow”
  • “Boiling”
  • “Falling oscillating spaghetti”
slide43

Self-consistent model

Orbital period 117.18331±0.00017minutes

Duration of eclipse 433.3 seconds

Distance to the system ~140 parsec

Mass of the red dwarf 0.163 MSun

Radius of the red dwarf 0.204RSun

Mass ratio q=0.3 (assuming similarity to the magnetic system AR UMa)

Mass of the white dwarf 0.543 MSun

Orbital separation 0.704 RSun=4.9*108m

Distance from the inner Lagrangian point to the white dwarf 3.04*108m

Illumination of the red dwarf~ 1.8% emission of the white dwarf

Radius of the white dwarf 0.013RSun=9.06*106m

Orbital velocity 437 km/s

Ascending/descending branch of the eclipse of the white dwarf: expected 20 sec, observed 3 sec

Size of the main emission region 1300 km

Orbital inclination 79-86 (79.1o)

Angle between the line of centers and the magnetic axis 50.3o

Angle between the line of centers and the accretion column’s axis in the intermediate state 38.9o

Dependence of accretion geometry on luminosity !

slide45

Self-consistent mathematical model of the exotic object OTJ 071126+440405= CSS 081231:071126+440405 is discussed. The system was discovered as a polar at the New year night 31.12.2008/01.01.2009 by D.Denisenko (VSNET Circ), and we have initiated an international campaign of photometric and polarimetric observations of this object (totally ~80 runs in Ukraine, Korea, Slovakia, Finland, USA). This work is a part of the "Inter-Longitude Astronomy" (ILA) project on monitoring of variable stars of different classes (Andronov et al., 2003). Results of this campaign will be published separately (Andronov et al., 2009). Here we present the geometrical and physical model of the system. In an addition to the usual assumption that cataclysmic variables contain a Roche-lobe filling red dwarf and an accreting white dwarf, we propose an interpretation of three types of the brightness minima, as the eclipses by the red dwarf, white dwarf and the accretion column itself (self-eclipse). In the low luminosity state, when the accretion rate is suggested to vanish, a "quiescence" is observed at the light curve, i.e. the optical flux comes from the illuminated secondary star and the non-accreting side of the white dwarf. When the accretion column becomes visible, the light curve exhibits a `hump" interrupted by the main eclipse by the red dwarf. In the "intermediate" luminosity state, the brightness increases at all phases, however, the main hump shifts to smaller phases and an additional minimum (self-eclipse) is observed. In this state, the emitting accreting region becomes larger, and is not significantly eclipsed by the white dwarf. The phase difference between the preliminary and main eclipses is smaller than in the high luminosity state, what is interpreted by the dependence of the position of the thread point, where magnetic field of the white dwarf captures the (initially ballistic) accretion stream. At the high state, the thread point approaches the cross-section of the ballistic stream with the magnetic axis, whereas at the intermediate state, the thread point may lie from 70% to 100% of the distance between the white dwarf and the inner Lagrangian point. As the ballistic trajectory nearly coincides with the magnetic field lines near the inner Lagrangian point, this argues for an "energetically optimal" orientation of the magnetic axis. As the system is of ~20 mag at minimum, no spectral observations were made to determine parameters of the red dwarf. From the statistical relationship, the mass of the red dwarf is estimated to be ~0.165 solar masses, for the white dwarf (from eclipse duration) - from 0.5 to 1.76 solar masses. As the system resembles ER UMa in some characteristics, the lower value may be assumed. The inclination of the system and other physical parameters are estimated. The object is an excellent laboratory to study multiple physical processes in the magnetic systems.