Microflares in accretion disks

¹ Indian Institute of Astrophysics, Bangalore 560034, India e-mail: vinod@iiap.ernet.in
² Tata Institute of Fundamental Research, Theoretical Astrophysics Group, Mumbai 400005, India
³ Institutt for Fysikk, NTNU – Norwegian University of Science and Technology, N7491, Trondheim, Norway e-mail: ramadura@phys.ntnu.no
⁴ Department of Physics & Astronomy, Georgia State University, Atlanta GA 30303, USA e-mail: wiita@chara.gsu.edu

Corresponding author: P. J. Wiita, wiita@chara.gsu.edu

Received: 20 July 2001
Accepted: 13 November 2002

Abstract

We have investigated the phenomenon of explosive chromospheric evaporation from an accretion disk as a mechanism for fast variability in accreting sources such as low mass X-ray binaries and active galactic nuclei. This has been done in the context of advection dominated accretion flows, allowing both high and low states to be considered. This mechanism can in principle produce sub-millisecond timescales in binaries and sub-minute timescales in active galaxies. However, even considering the possibility that large numbers of these microflares may be present simultaneously, the power emitted from these microflares probably amounts to only a small fraction of the total X-ray luminosity.