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Astron. Astrophys. 336, 220-230 (1998)

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On the outburst light curves of soft X-ray transients as response of the accretion disk to mass deposition

Ünal Ertan and M. Ali Alpar

Physics Department, Middle East Technical University, Ankara 06531, Turkey (ertan@newton.physics.metu.edu.tr; alpar@newton.physics.metu.edu.tr)

Received 7 October 1997 / Accepted 8 April 1998

Abstract

We note that the solution of accretion disk dynamics for an initial delta-function mass distribution gives a light curve that fits both the rise and the decay pattern of the outburst light curves of black-hole soft X-ray transients (BSXTs) until the onset of the first mini outburst quite well. The Green's function solution of Lynden-Bell & Pringle (1974) is employed for two different time-independent viscosity laws to calculate the expected count rates of X-ray photons in the Ginga energy bands as a function of time. For both models basic characteristics of the outburst light curves of two typical sources GS 2000+25 and  GS/GRS 1124-68 are reproduced together with plausible values of the thin disk parameter [FORMULA] and the recurrence times. This agreement with the outburst light curves and the source properties during quiescence support the idea of mass accumulation and the sporadic release of accumulated mass at the outer disk.

Key words: black hole physics – accretion, accretion discs – novae, cataclysmic variables – X-rays: stars

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© European Southern Observatory (ESO) 1998

Online publication: July 7, 1998
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