Journal Article

Fast variability as a tracer of accretion regimes in black hole transients

T. Muñoz-Darias, S. Motta and T. M. Belloni

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 410, issue 1, pages 679-684
Published in print January 2011 | ISSN: 0035-8711
Published online December 2010 | e-ISSN: 1365-2966 | DOI:
Fast variability as a tracer of accretion regimes in black hole transients

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We present the root mean square (rms)–intensity diagram for black hole transients. Using observations taken with the Rossi X-ray Timing Explorer, we study the relation between the rms amplitude of the variability and the net count rate during the 2002, 2004 and 2007 outbursts of the black hole X-ray binary GX 339−4. We find that the rms–flux relation previously observed during the hard state in X-ray binaries does not hold for the other states, when different relations apply. These relations can be used as a good tracer of the different accretion regimes. We identify the hard, soft and intermediate states in the rms–intensity diagram. Transitions between the different states are seen to produce marked changes in the rms–flux relation. We find that one single component is required to explain the ∼40 per cent variability observed at low count rates, whereas no or very low variability is associated to the accretion-disc thermal component.

Keywords: accretion, accretion discs; black hole physics; binaries: close; X-rays: binaries; X-rays: individual: GX 339−4

Journal Article.  4099 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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