On the outburst light curves of black hole soft X-ray transients

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2002

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Ertan, Ünal

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We explore the X-ray outburst light curves of black-hole soft X-ray transients. First, the analytical solutions for pure viscous disk evolution are investigated by using the time independent kinematic viscosities in the form v <x RP. The illustrative viscosity models which give best fits to the observed X-ray data with reasonable initial conditions are also examined through the observed in ner disk properties in quiescence. It is seen that the viscosity law power law index (p ~ 1) can account for both the observed main outburst and the quies cent X-ray emission with this time independent form of the kinematic viscosity. Next, we suggest a new scenario to explain the outburst light curves of black- hole soft X-ray transients together with the secondary maximum and bump iiiseen on their decay phases. Our explanations are based on the disk instability models considering the effect of X-ray irradiation. The scenario is in good agreement with the observed X-ray delays by a few days with respect to the optical rise for both the main outburst and the later maxima. We test our scenario by numerically solving the disk diffusion equation using the temper ature dependent standard a- viscosities. The obtained model curve fits well to the observed X-ray outburst photon flux curve of the black-hole soft X-ray transient GS/GRS 1124-68, which is a typical representative of the canonical black-hole soft X-ray transients.

Subject Keywords

Black holes (Astronomy), Neutron stars, Accretion (Astrophysics), Soft X-ray transients, Accretion disks, Disk dynamics model

URI

https://hdl.handle.net/11511/12798

Collections

Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

Ü. Ertan, “On the outburst light curves of black hole soft X-ray transients,” Ph.D. - Doctoral Program, Middle East Technical University, 2002.