Recent Progress in Modelling of Accretion Discs in AM CVn Stars - - PowerPoint PPT Presentation

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Recent Progress in Modelling of Accretion Discs in AM CVn Stars - - PowerPoint PPT Presentation

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Recent Progress in Modelling of Accretion Discs in AM CVn Stars Thorsten Nagel D.-J. Kusterer, T. Rauch, D. Semionov, K. Werner Institut fr Astronomie und Astrophysik Kepler Center for Astro and Particle Physics Universitt Tbingen Sept.

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Recent Progress in Modelling of Accretion Discs in AM CVn Stars

Thorsten Nagel

D.-J. Kusterer, T. Rauch, D. Semionov, K. Werner Institut für Astronomie und Astrophysik Kepler Center for Astro and Particle Physics Universität Tübingen

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Outline

Modelling of NLTE Accretion Discs Model grid for AM CVn systems Model vs. CE 315 Accretion Disc Wind – First Steps Summary

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Modelling of NLTE Accretion Discs

Assumptions: geometrically thin α-disc (Shakura & Sunyaev 1973) axial symmetry Divide disc into set of concentric rings Each ring: plane-parallel radiating slab Calculate detailed vertical structure and synthetic spectrum with AcDc (Accretion Disc code, Nagel et al.

2004)

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Modelling of Accretion Discs

hydrostatic equilibrium (gas and radiation pressure) radiative equilibrium (full line blanketing, no convection) NLTE rate equations radiation transfer eqs. (irradiation by primary can be considered)

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Modelling of Accretion Discs

Vertical structure and spectrum for each disc ring Integration of all disc ring intensities, rotational broadening ⇒ NLTE accretion disc spectra for different inclinations disc spectrum can be used as input for our accretion disc wind models

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Modelling of Accretion Discs

Input parameters

mass and radius of central object mass accretion rate radial extension of accretion disc Reynolds number chemical abundances (→ donor star) irradiation: temperature/spectrum of central object irradiation angle

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SLIDE 7
  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Model grid for AM CVn stars

mass of primary: 0.6, 0.8, 1.0, 1.2 and 1.4 M☺ mass accretion rate: 10-8, 10-9, 10-10, 10-11 M☺/yr variation of C, N, O, Si abundances radially extended to the tidal radius (if possible) five inclination angles

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Model grid for AM CVn stars

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2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Variation of primary mass

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Variation of mass-accretion rate

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Variation of chem. abundances

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Variation of chem. abundances

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Variation of inclination

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2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Influence of irradiation by primary

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2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Influence of irradiation by primary

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Spectroscopic detection of primary

so far only one directly spectroscopical detection of white dwarf primary (Sion et al. 2006) in which systems should we look, in which wavelength range ?

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Spectroscopic detection of primary

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Models vs. Observation: CE 315

(spectrum by Ruiz et al. 2001)

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SLIDE 19
  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Models vs. Observation: CE 315

(spectrum by Ruiz et al. 2001)

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Models vs. Observation: CE 315

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Accretion Disc Wind

P Cygni profile

(Wade 2002)

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Accretion Disc Wind

WOMPAT: Wind mOdel in Monte carlo Parallel rAdiative Transfer (D. Kusterer 2008, PhD Thesis) parallelized Monte Carlo code LTE occupation numbers iterative solution of temperature and ionisation structure calculated disc spectrum or blackbody as input

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Accretion Disc Wind

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2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Accretion Disc Wind

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  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Summary

grid of accretion disc models:

0.6 - 1.4 M☺ 10-8 - 10-11 M☺/y

reproduction of absorption and emission line spectra for high and low state irradiation by the primary seems to have almost no effect onto the spectrum

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SLIDE 26
  • Sept. 4th 2008

2nd Int. Workshop on AM CVn Stars 1 – 5 Sept. 2008 Cape Town, South Africa

Summary

spectroscopic detection of primary best possible in UV indication of underabundance of Si in CE315

(also no Si found in X-ray [Ramsay et al. 2006] and UV [Gänsicke et al. 2003])

Monte Carlo based accretion disc wind