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2000MNRAS.314..498M - Mon. Not. R. Astron. Soc., 314, 498-510 (2000/May-3)
Disc instability models for X-ray transients: evidence for evaporation and low α-viscosity?.
MENOU K., HAMEURY J.-M., LASOTA J.-P. and NARAYAN R.
Abstract (from CDS):
Removing the inner, most unstable, parts of the accretion disc increases the predicted recurrence times. However, DIMs with values of the viscosity parameter αhot∼0.1 and αcold∼0.02 (values typically used in applications of the DIM to standard dwarf nova outbursts) fail to reproduce the long recurrence times of soft X-ray transients (unless we resort to fine-tuning the parameters), independent of the evaporation strength. We show that models in which evaporation is included and a smaller value of αcold (∼0.005) used do reproduce the long recurrence times and the accretion rates at the level of the Eddington rate observed in outburst. The large difference between the values of αhot and αcold, if confirmed once disc irradiation is included, suggests that several viscosity mechanisms operate in these accretion discs.
For some parameter sets our models predict re-flares during the decline from outburst. The re-flares are a physical property of the model and result from the formation of a heating front in the wake of an initial cooling front, and subsequent multiple front reflections. The re-flares disappear in low-α models where front reflection cannot occur.
Abstract Copyright: 2000, Royal Astronomical Society
Journal keyword(s): accretion, accretion discs - black hole physics - MHD - turbulence - novae, cataclysmic variables - X-rays: stars.
Simbad objects: 10
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