Investigations of the accretion disk structure in SS Cyg using the Doppler tomography technique D.A.Kononov Institute of Astronomy of the RAS Russia, Moscow

Introduction

Close binary systems are interesting from the observational point of view as well as from the point of view of studying physical processes running in the systems. The bulk of the emission are caused by accretion and processes taking place in the accretion disc and in the circumbinary envelope.

Gas dynamical features are difficult to be observed directly because the systems are small and are not to be resolved from direct observations. How might one cope with this problem?

Radon transform - normalized local profile The method of Doppler tomography

I(VR,φ) → I(Vx, Vy)

But!

Unfortunately direct transform from velocities to coordinates is impossible without initial assumptions about the density, temperature and velocity distribution.

I(V x,V y ) → I(x,y) – impossible.

Unfortunately direct transform from velocities to coordinates is impossible without initial assumptions about the density, temperature and velocity distribution. I(V x,V y ) → I(x,y) – impossible. However, we can easily turn the numerically calculated distribution of the intensity from the coordinate frame into the velocity frame.

Unfortunately direct transform from velocities to coordinates is impossible without initial assumptions about the density, temperature and velocity distribution. I(V x,V y ) → I(x,y) – impossible. However, we can easily turn the numerically calculated distribution of the intensity from the coordinate frame into the velocity frame. I(x,y) → I(V x,V y ) – possible.

In our work we have started from observations and transform them to observational Doppler tomograms. At the same time we performed gas dynamic simulations of the system and computed a synthetic Doppler map. Comparison of the synthetic map with the observational tomograms allows us to identify the main features of the flow structure.

Primary Secondary WD Red Dwarf (K 4.5 V) M ≈ 0.97M ๏ M ≈ 0.56M ๏ Teff ≈30000 K Teff ≈ 3500 K Ṁ ≈ M ๏ /year A ≈ 2.05 R ๏ P ≈ 6.6 h

Observations

2 meter telescope Ziess-2000 in the Terskol Observatory. Classical spectrograph in the Cassegrain focus Dates of observations:2006/08/05, 2006/12/08, 2006/12/10, 2006/12/13 (outbursts), 2006/08/14 (quiescence) Exposure times τ = 10 min (2006/08/05), τ = 15 min (all other dates) Lines: Hα, H β, H γ

Quiescent state

Raw spectrum

Doppler tomography of H β, H γ

Maximum Entropy Image Restoration

3D gas dynamic simulations

Density distribution in the equatorial plane and the velosity vectors

Intensity distribution in the equatorial plane

Identification of the main gas dynamic features in SS Cyg in quiescence.

Synthetic Doppler map Intensity distribution in the equatorial plane

Synthetic Doppler map Intensity distribution in the equatorial plane

Synthetic Doppler map Intensity distribution in the equatorial plane

Synthetic Doppler map Intensity distribution in the equatorial plane

Synthetic Doppler map Intensity distribution in the equatorial plane

Intensity distribution in the equatorial plane Synthetic Doppler map

Intensity distribution in the equatorial plane

Synthetic Doppler map Intensity distribution in the equatorial plane

H 

H 

Outburst

Observational data analysis Profiles of the Hα,Hβ and Hγ lines

Observational data analysis Profiles of the Hβ and Hγ lines

Observational data analysis Orbital evolution of the line profiles

Observational data analysis Long term line profiles evolution

Outburst model

Donor’s surface (L1 point) Z X

Hα line.

H α Doppler map of the system

Conclusion Quiescence Observational tomograms clearly show presence of the disc in the system. Performed analysis shows that the main contribution to the intensity of the emission during quiescence is provided by: arms of the tidal spiral shock, hot line, and the region near the bow shock.

During outburst five flow regions contribute to the line formation: outer parts of the disk’s remnant, region of the donor’s surface near the L 1 point, toroidal envelope around the accretor, spherical envelope around the accretor, and the region near the bow shock. Conclusion Outburst