dens.wr140.0021.gif dens.wr140.0128.gif dens.wr140.0142.gif dens.wr140.0152.gif 3D symbiotics spectrum 2 spectrum 3 spectrum 4 line profiles interaction zone interpolatet density nitrogen, y-axis nitrogen, z-axis Gamma Vel orbit Gamma Vel X-ray RW Hya streamlines RW Hya disk



Hot star binaries

by Doris Folini and Rolf Walder



Page contents

Introduction
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Eccentric orbit of WR140
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X-ray light curve of gamma velorum
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NLTE radiative transfer for the wind-wind collision zone in gamma Velorum
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Orbital line profile variations in symbiotic binaries
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Wind accretion in RW Hya
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References
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Introduction

The 3D distribution of the circumstellar matter in hot star binaries, in particular WR+O star binaries and symbiotic binaries, has interested us for a long time. What can we learn from observed light curves or line profile variations on the circumstellar matter distribution? Is this matter distribution determined by the collision of the two stellar winds or by something else, for example accretion onto one of the two components? To what degree can we determine the parameters of the two stellar winds from such observation?

We examine these questions by means of multidimensional simulations of such binary star systems, using the different codes of our A-MAZE package.


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WR + O binaries

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Eccentric orbit of WR140

WR 140 is a WR+O binary with a very excentric orbit. Around periastron passage, dust is observed. We have used our AMRCART codes to perform a 3D hydrodynamical simulation of WR140. One of the goals is to study how the shape and central density of the wind-wind interaction zone changes over one orbit.
dens.wr140.0021.gif dens.wr140.0128.gif
dens.wr140.0142.gif dens.wr140.0152.gif
Density in orbital plane. Click on images to enlarge or watch a mpeg-video (3.0MB) or a quicktime video (5.9MB).


The X-ray light curve of gamma Velorum

The observed X-ray light curve of gamma Velorum, found in the literature, shows a distinct asymmetry. We propose that this asymmetry is largely due to the effect of the colliding wind interaction zone present in gamma Velorum. To corroborate this idea, we have performed a 3D adiabatic hydrodynamical simulation of the WR+O binary gamma Velorum. This yields us a 3D density distribution as a function of orbital phase.
Subsequently, we have used this density distribution to estimate the diminution of X-rays emitted in the central regions of the wind-wind collision zone. We assume that the emitted X-ray flux is diminished according to flux = flux0*exp(-kappa*col.dens), where kappa = 5*10^23 cm^-2 and col.dens is the column density between the source and the observer. In this way, and for a proper orientation of the system with respect to the observer, we obtain the synthetic X-ray light curve shown below in blue. Red are observed data points. Click on images to enlarge.

Gamma Vel orbit Gamma Vel X-ray



NLTE radiative transfer for the wind-wind collision zone in gamma Velorum

What ionization states occur in the wind-wind collision zone of gamma Velorum? We have performed 3D isothermal hydrodynamical simulations of the system. The 3D density and velocity distribution we have obtained in this way, we have subsequently used as input for our 3D NLTE optically thick radiative transfer code TR3D to calculate the ionization state of the interaction zone. Our results so far suggest that optically thick effects do become important in this context. However, due to the limited spatial resolution we could achieve these results are preliminary only. Click on individual regions to enlarge. wind-wind collision


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Symbiotic binaries

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Orbital line profile variations in symbiotic binaries

We are interested in how far orbital line profile variations of optically thin, Doppler broadened lines can be used to determine the circumstellar matter distribution in symbiotic binaries. In addition, we are interested in what such line profile variations can tell us about the wind parameters of the two stars.

We have run 3D adiabatic, hydrodynamical simulations of three different model symbiotic systems, which differ in their wind parameters. We then have assumed different temperatures and luminosities for the white dwarf and have used D3NEBEL to calculate the resulting nebular spectrum for each possible combination of temperature, luminosity, and the three calculated 3D density distribution. Click on figure to enlarge. 3D symbiotics

Studying the synthetic spectra we obtain, we find that it should indeed be possible to infer, within limits, the 3D density distribution and the wind parameters of the stars from the variation of Doppler broadened line profiles over one orbit. Click on individual parts to enlarge. line profiles


Wind accretion in RW Hya

For the symbiotic system RW Hya we have used 3D hydrodynamical simulation to examine a wind accretion scenario. What would the circumstellar matter distribution look like if, instead of both stars having a wind, the white dwarf were to accrete matter from the red giant? The simulations show the formation of a pronounced accretion wake and an accretion disk around the white dwarf. Click on individual regions for enlargements.
RW Hya
Maybe this could explain a prominent dip in the observed emission of RW Hya, which repeats with the orbital phase, but occurs not at eclipse. More details on this point you find in the paper by Dumm et al., listed in the reference section.


References

R. Walder and D. Folini
3D-hydrodynamics of colliding winds in massive binaries
IAU Symposium No. 212, 2002, 7 pages, to appear
(Available as a 1.0MB gzipped ps-file)

D. Folini and R. Walder
Theoretical predictions for the cold part of the colliding wind interaction zone
PASP conference series, 260, 605-614, 2002
(Available as a 473KB gzipped ps-file)

R. Walder and D. Folini
Theoretical consideration of colliding clumped winds
PASP conference series, 260, 595-603, 2002.
(Available as a 280KB gzipped ps-file)

D. Folini and R. Walder
Theory of thermal and ionization effects in colliding winds of WR+O binaries
ASP conference series 204, 267-278, 2000
(Available as a 63KB gzipped ps-file)

R. Walder and D. Folini
Complex wind dynamics and ionization structure in symbiotic binaries
ASP conference series 204, 331-342, 2000
(Available as a 228KB gzipped ps-file)

D. Folini and R. Walder
3D hydrodynamical simulations of colliding wind binaries: theory confronts observations
Astrophysics and Space Science 274, 189--194, 2000
(Available as a 251KB gzipped ps-file)

T. Dumm, D. Folini, H. Nussbaumer, H. Schild, W. Schmutz, and R. Walder
A wind accretion wake in RW Hydrae? Astronomy and Astrophysics, 354, 1014--1020, 2000
(Available as a 229KB gzipped ps-file)

D. Folini and R. Walder and Simin Motamen
Colliding winds in WR binaries: further developments within a complicated story
IAU Symposium No. 193, 298-305, 1999
(Available as a 1.2MB gzipped ps-file)

D. Folini
Computational approaches to multidimensional radiative transfer and the physics of radiative colliding flows
PhD Thesis, ETH No. 12606, 1998
(Available as a 3.3 MB gzipped ps-file)

R. Walder
Some Aspects of the Computational Dynamics of Astrophysical Nebulae
PhD Thesis, ETH No. 10302, 1994
(Available upon request)



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Doris Folini and Rolf Walder
Last Update: October 14, 2002