Presentation on theme: "Gamow conference, Odessa, 20.08.2009 Ivan L. Andronov Odessa National Maritime University Space Laboratory to Study Accretion in Magnetic Cataclysmic Variables:"— Presentation transcript:
Gamow conference, Odessa, Ivan L. Andronov Odessa National Maritime University Space Laboratory to Study Accretion in Magnetic Cataclysmic Variables: The Case of Exotic Newly-Discovered Polar OTJ
Theoretical part of the international observational campaign
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 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)
General model depends on characteristic dimensions: R wd – radius of the white dwarf R A -Alfven Radius (magnetosphere) R c - co-rotation radius R d - maximum dimension of disk R L – distance to the inner Lagrangian point a – orbital separation Always: R wd
Types of Variability: Non-Magnetic Nova-like Dwarf Novae IP asynchr classical Magnetic (polars) Characteristic timescale
New Year 2008/2009
Theoretical models of 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 Gravitation Coriolis force Centrifugal force Viscosity Gas pressure Magnetic channeling
Theoretical models of 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
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 HJD min = (14) + 0, (12) × (Е –16347).
“Var-Comp” instrumental VR magnitudes The orbital “dip” was removed HJD spin = (13) (30) *Е (2004г.) spin wide 1 spin narrow 2
Three types of minima orbital "dips" spin wide 1 spin narrow 2 | 1 orbital period 2 spin period migrating minima beat period ~60 days 4 subsequent nights from 18 Andronov, Baklanov & Burwitz (2005)
Synchronization of the white dwarf (acceleration of the “slow” spin rotation): HJD spin = (74) (23) *Е (11) *Е 2 ( ) HJD spin = (13) (30) *Е (2004)
Period variations: T E = T0+P*Е + Q* Е 2 dP/dt=2Q/P, (dP/dt)/P=2Q/P 2 Q= (Staubert et al. 2003, 1.5 ) Q= (Mukai et al. 2003, 9 ) Q=-7.81(11) (all data: , 61 ) Theory: AM Her (similar parameters) : 6< <260 yrs (Andronov 1982) Observations: BY Cam (Silber et al. (1997), Mason et al. ), V1500 Cyg (Pavlenko and Pelt (1988), Pavlenko and Shugarov 2005)
Distances from the center of the white dwarf to: a – center of the secondary R L – inner Lagrangian point R Y – Roche lobe in the orbital plane (“Y”) R HS – “hot spot” (Warner & Peters 1972) 16R WD – minimal capture radius R WD – surface of the white dwarf + Andronov & Baklanov (Af 2007)
Two limiting models of the accretion columns : 1 - “vertical” (or height > radius) (hope that the truth is somewhere in between): Δφ R 0 / R WD (model 1) R 0 / R WD (model 2) "corridor" of model 1 model 2 white dwarf dipole magnetic field line φ+ ψ (φ)= π(1-2Δφ)/2
Results (briefly): Most precise: Orbital period Spin period Spin period variations + synchronization time Beat period of d 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
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)
Crimean Astrophysical Observatory: AZT-11 reduced with WinFits by L.L.Chinarova: Measuring all S.V.Kolesnikov (reduced with MUNIpack by V.V.Breus): Faint minima missing
BVRI photometry at the Korean Mt. Lemmon Observatory: 1m
unfiltered photometry in Finland: changing states of luminosity & pre-dip shift
unfiltered photometry in Finland: fall <5 sec
Crimean Astrophysical Observatory: ZTSh (1 sec) – S.V.Kolesnikov, N.M.Shakhovskoy Reduced with ZTShServer (V.V.Breus) Wide R filter (intensities “var/comp”)
These studies of the magnetic cataclysmic variables were initiated in 1978 by Prof. Vladimir P.Tsessevich ( ) when I was a 3-rd year student and was interested in mathematical modeling of unstable Universe, black holes, gravitational lenses and pulsations
Need for monitoring to check dynamics of the object. Otherwise: antigravitation maybe?
Arto Oksanen (Finland) : 3 unexpectedly different luminosity states
Theoretical models of magnetic binary stars 2D - oscillations of the orientation of the magnetic axis Red dwarf White dwarf
Theoretical models of magnetic binary stars 3D - oscillations of the orientation of the magnetic axis
Theoretical models of magnetic binary stars “Swinging dipole" – excitation of the auto- oscillations of the orientation of the magnetic axis with characteristic time of ~1-10 years
Model of Dipole+thin disk: Dependence of the equilibrium period on the orientation (Andronov 2005)
Spin phase variability as function of the orbital phase +correlated irregular shifts: clues for determination of the column orientation Kim, Andronov et al. (2005)
Angular characteristics of the Roche lobe (Andronov, 1992) Improved expressions presented In the poster: Andronov & Breus, this conf.
Модель затменного поляра OTJ Модель затменного поляра OTJ Dependence of the eclipse duration (in degrees) on the orbital inclination for various values of the mass of the white dwarf
Dependence of the orbital inclination on the mass of the white dwarf
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 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 stars Advanced models of the “Standard” accretion column : Non-homegeneous Asymmetric Inclined “Rainbow” “Boiling” “Falling oscillating spaghetti”
"Rainbow" Accretion Column
Self-consistent model Orbital period ± minutes Duration of eclipse seconds Distance to the system ~140 parsec Mass of the red dwarf M Sun Radius of the red dwarf R Sun Mass ratio q=0.3 (assuming similarity to the magnetic system AR UMa) Mass of the white dwarf M Sun Orbital separation R Sun =4.9*10 8 m Distance from the inner Lagrangian point to the white dwarf 3.04*10 8 m Illumination of the red dwarf ~ 1.8% emission of the white dwarf Radius of the white dwarf 0.013R Sun =9.06*10 6 m 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 (79.1 o ) Angle between the line of centers and the magnetic axis 50.3 o Angle between the line of centers and the accretion column’s axis in the intermediate state 38.9 o Dependence of accretion geometry on luminosity !
3D Model: I.L.Andronov; animation: V.V.Breus
Self-consistent mathematical model of the exotic object OTJ = CSS : is discussed. The system was discovered as a polar at the New year night / 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.